Global Technical Regulation No. 8
|Name:||Global Technical Regulation No. 8|
|Description:||Electronic Stability Control Systems.|
|Official Title:||Electronic Stability Control Systems.|
|Country:||ECE - United Nations|
|Date of Issue:||2008-06-26|
|Amendment Level:||Corrigendum 2 of October 28, 2011|
|Number of Pages:||70|
|Vehicle Types:||Bus, Car, Component, Heavy Truck, Light Truck|
|Subject Categories:||Braking, Steering, Wheels and Tyres|
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All InterRegs documents are formatted as PDF files and contain the full text, tables, diagrams and illustrations of the original as issued by the national government authority. We do not re-word, summarise, cut or interpret the regulatory documents. They are consolidated, published in English, and updated on a regular basis. The following text extract indicates the scope of the document, but does not represent the actual PDF content.
October 28, 2011
Created on November 18, 2004, Pursuant to Article 6 of the
AGREEMENT CONCERNING THE ESTABLISHING OF GLOBAL TECHNICAL
REGULATIONS FOR WHEELED VEHICLES, EQUIPMENT AND PARTS WHICH
CAN BE FITTED AND/OR BE USED ON WHEELED VEHICLES
(ECE/TRANS/132 and Corr.1)
DONE AT GENEVA ON JUNE 25, 1998
GLOBAL TECHNICAL REGULATION NO. 08
ELECTRONIC STABILITY CONTROL SYSTEMS
(ESTABLISHED IN THE GLOBAL REGISTRY ON JUNE 26, 2008)
dated January 26, 2009
dated October 28, 2011
GLOBAL TECHNICAL REGULATION NO. 08
A. STATEMENT OF TECHNICAL RATIONALE AND JUSTIFICATION
1. In spite of the technological advances and regulatory efforts of the past few decades, the
global burden to society associated with motor vehicle crashes remains considerable.
According to the World Health Organization (WHO), each year there are more than one
million fatalities and two million injuries in traffic crashes worldwide, and the global annual
economic cost of road crashes is nearly $600 billion. These human and economic losses
are distributed across regions, including approximately 40,000 fatalities annually in Europe,
over 40,000 in the United States, over 90,000 in India, and over 100,000 in China.
Therefore, regulators and others with an interest in vehicle safety and public health shall
carefully monitor the development of new technologies, which may offer the potential to
reduce the mortality, morbidity, and economic burdens associated with vehicle crashes.
Current research demonstrates that electronic stability control (ESC) systems represent a
mature technology, which could have the most significant life-saving potential since the
advent of the seat belt. ESC systems are particularly effective in preventing single-vehicle,
run-off-road crashes (many of which result in rollover).
2. Crash data studies conducted in the United States of America (U.S.), Europe, and Japan
indicate that ESC is very effective in reducing single-vehicle crashes. Studies of the
behaviour of ordinary drivers in critical driving situations (using a driving simulator) show a
very large reduction in instances of loss of control when the vehicle is equipped with ESC,
with estimates that ESC reduces single-vehicle crashes of passenger cars by 34% and
single-vehicle crashes of sport utility vehicles (SUVs) by 59%. The same recent U.S. study
showed that ESC prevents an estimated 71% of passenger car rollovers and 84% of SUV
rollovers in single-vehicle crashes. ESC is also estimated to reduce some multi-vehicle
crashes, but at a much lower rate than its effect on single-vehicle crashes. It is evident that
the most effective way to reduce deaths and injuries in rollover crashes is to prevent the
rollover crash from occurring, something which ESC can help accomplish by increasing the
chances for the driver to maintain control and to keep the vehicle on the roadway. It is
expected that potential benefits would be maximized by fleet-wide installation of ESC
systems meeting the requirements of this gtr. The following discussion explains in further
detail the nature of the identified safety problem and how ESC systems can act to mitigate
2. TARGET POPULATION: SINGLE-VEHICLE CRASH AND ROLLOVER STATISTICS
3. Although vehicle and road conditions may vary in different countries and regions, it is
anticipated that the experience with ESC, as reported in European, U.S., and Japanese
research studies, would be generally applicable across a range of driving environments.
The following information, based upon statistical analyses of U.S. data is illustrative of the
types of crashes that could potentially be impacted by a global technical regulation for ESC.
9. In order to counter such situations in which loss of control may be imminent, ESC uses
automatic braking of individual wheels to adjust the vehicle's heading if it departs from the
direction the driver is steering. Thus, it prevents the heading from changing too quickly
(spinning out) or not quickly enough (plowing out). Although it cannot increase the available
traction, ESC affords the driver the maximum possibility of keeping the vehicle under control
and on the road in an emergency manoeuvre using just the natural reaction of steering in
the intended direction. Keeping the vehicle on the road prevents single-vehicle crashes,
which are the circumstances that lead to most rollovers. However, there are limits to an
ESC system's ability to intervene effectively in such situations. For example, if the speed is
simply too great for the available road traction, even a vehicle with ESC will unavoidably drift
off the road (but not spin out). Furthermore, ESC cannot prevent road departures due to
driver inattention or drowsiness rather than loss of control. Nevertheless, available research
from around the world has shown that given their high effectiveness rate, ESC systems
would have a major life-saving impact, particularly once there is wide fleet penetration.
Mechanism of Action by Which ESC Prevents Loss of Vehicle Control
10. The following explanation of ESC operation illustrates the basic principle of yaw stability
control. An ESC system maintains "yaw" (or heading) control by comparing the driver's
intended heading with the vehicle's actual response, and automatically turning the vehicle if
its response does not match the driver's intention. However, with ESC, turning is
accomplished by applying counter torques from the braking system rather than from
steering input. Speed and steering angle are used to determine the driver's intended
heading. The vehicle response is determined in terms of lateral acceleration and yaw rate
by onboard sensors. If the vehicle is responding in a manner corresponding to driver input,
the yaw rate will be in balance with the speed and lateral acceleration.
11. The concept of "yaw rate" can be illustrated by imagining the view from above a car
following a large circle painted on a parking lot. One is looking at the top of the roof of the
vehicle and seeing the circle. If the car starts in a heading pointed north and drives half way
around the circle, its new heading is south. Its yaw angle has changed 180°. If it takes
10 seconds to go half way around the circle, the "yaw rate" is 180° per 10 seconds or
18 deg/sec. If the speed stays the same, the car is constantly rotating at a rate of
18 deg/sec around a vertical axis that can be imagined as piercing its roof. If the speed is
doubled, the yaw rate increases to 36 deg/sec.
12. While driving in a circle, the driver notices that he shall hold the steering wheel tightly to
avoid sliding laterally. The braking force is necessary to overcome the lateral acceleration
that is caused by the car following the curve. The lateral acceleration is also measured by
the ESC system. When the speed is doubled, the lateral acceleration increases by a factor
of four if the vehicle follows the same circle. There is a fixed physical relationship between
the car's speed, the radius of its circular path, and its lateral acceleration.
13. The ESC system uses this information as follows: Since the ESC system measures the
car's speed and its lateral acceleration, it can compute the radius of the circle. Since it then
has the radius of the circle and the car's speed, the ESC system can compute the correct
yaw rate for a car following the path. The system includes a yaw rate sensor, and it
compares the actual measured yaw rate of the car to that computed for the path the car is
following. If the computed and measured yaw rates begin to diverge as the car that is trying
to follow the circle speeds up, it means the driver is beginning to lose control, even if the
driver cannot yet sense it. Soon, an unassisted vehicle would have a heading significantly
different from the desired path and would be out of control either by oversteering (spinning
out) or understeering.
Oversteering. In Figure 1 (bottom panel), the vehicle has entered a left curve that is
extreme for the speed it is travelling. The rear of the vehicle begins to slide which
would lead to a vehicle without ESC turning sideways (or "spinning out") unless the
driver expertly countersteers. In a vehicle equipped with ESC, the system
immediately detects that the vehicle's heading is changing more quickly than
appropriate for the driver's intended path (i.e. the yaw rate is too high). It momentarily
applies the right front brake to turn the heading of the vehicle back to the correct path.
The action happens quickly so that the driver does not perceive the need for steering
corrections. Even if the driver brakes because the curve is sharper than anticipated,
the system is still capable of generating uneven braking if necessary to correct the
Understeering. Figure 1 (top panel) shows a similar situation faced by a vehicle
whose response as it nears the limits of road traction is to slide at the front ("plowing
out" or understeering) rather than oversteering. In this situation, the ESC system
rapidly detects that the vehicle's heading is changing less quickly than appropriate for
the driver's intended path (i.e. the yaw rate is too low). It momentarily applies the left
rear brake to turn the heading of the vehicle back to the correct path.
15. While Figure 1 may suggest that particular vehicles go out of control as either vehicles
strictly prone to oversteer or vehicles strictly prone to understeer, it is just as likely that a
given vehicle could require both understeer and oversteer interventions during progressive
phases of a complex avoidance manoeuvre such as a double lane change.
16. Although ESC cannot change the tyre/road friction conditions the driver is confronted with in
a critical situation, there are clear reasons to expect it to reduce loss-of-control crashes, as
17. In vehicles without ESC, the response of the vehicle to steering inputs changes as the
vehicle nears the limits of road traction. All the experience of the average driver is in
operating the vehicle in its "linear range" (i.e. the range of lateral acceleration in which a
given steering wheel movement produces a proportional change in the vehicle's heading).
The driver merely turns the wheel the expected amount to produce the desired heading.
Adjustments in heading are easy to achieve because the vehicle's response is proportional
to the driver's steering input, and there is very little lag time between input and response.
The car is travelling in the direction it is pointed, and the driver feels in control. However, at
lateral accelerations above about one-half "g" on dry pavement for ordinary vehicles, the
relationship between the driver's steering input and the vehicle's response changes (toward
oversteer or understeer), and the lag time of the vehicle response can lengthen. When a
driver encounters these changes during a panic situation, it adds to the likelihood that the
driver will lose control and crash because the familiar actions learned by driving in the linear
range would not be the correct steering actions.
18. However, ordinary linear range driving skills are much more likely to be adequate for a
driver of an ESC-equipped vehicle to avoid loss of control in a panic situation. By
monitoring yaw rate and sideslip, ESC can intervene early in the impending loss-of–control
situation with the appropriate brake forces necessary to restore yaw stability before the
driver would attempt an over-correction or other error. The net effect of ESC is that the
driver's ordinary driving actions learned in linear range driving are the correct actions to
control the vehicle in an emergency. Also, the vehicle will not change its heading from the
desired path in a way that would induce further panic in a driver facing a critical situation.
24. The difference between a roll stability control intervention and an oversteer intervention by
the ESC system operating in the basic yaw stability control mode is the triggering
circumstance. The oversteer intervention occurs when the vehicle's excessive yaw rate
indicates that its heading is departing from the driver's intended path, but the roll stability
control intervention occurs when there is a risk the vehicle could roll over. Thus, the roll
stability control intervention occurs when the vehicle is still following the driver's intended
path. The obvious trade-off of roll stability control is that the vehicle shall depart to some
extent from the driver's intended path in order to reduce the lateral acceleration from the
level that could cause tip-up.
25. If the determination of impending rollover that triggers the roll stability intervention is very
certain, then the possibility of the vehicle leaving the roadway as a result of the roll stability
intervention represents a lower relative risk to the driver. Obviously, the most effective
systems are ones that intervene only when absolutely necessary and then with the minimum
loss of lateral acceleration to prevent rollover. However, roll stability control is a new
technology that is still evolving.
26. Furthermore, there is currently insufficient data to evaluate the effectiveness of many of
these additional features, including roll stability control, either because their implementation
is not widespread or because it is too soon for actual crash statistics to illuminate its
practical effect on crash reduction. This is in contrast to the fundamental ESC system
described above for which a substantial amount of data exists.
4. EFFECTIVENESS OF ESC SYSTEMS
Overview of ESC Effectiveness in Preventing Single-Vehicle and Rollover Crashes
27. The following discussion explains in detail relevant research findings related to the
anticipated effectiveness of ESC systems. Electronic stability control can directly reduce a
vehicle's susceptibility to on-road untripped rollovers as measured by the "fishhook" test.
The direct effect is mostly limited to untripped rollovers on paved surfaces. However,
untripped on-road rollovers are a relatively infrequent type of rollover crash.
28. In contrast, the vast majority of rollover crashes occur when a vehicle runs off the road and
strikes a tripping mechanism such as soft soil, a ditch, a curb or a guardrail. The purpose of
ESC is to assist the driver in keeping the vehicle on the road during impending
loss-of-control situations. In this way, it can prevent the exposure of vehicles to off-road
Crash Data Studies of ESC Effectiveness
33. There have been a number of studies of ESC effectiveness in Europe and Japan beginning
in 2003. All of them have shown large potential reductions in single-vehicle crashes as a
result of ESC. Additionally, a preliminary U.S. study published in September 2004 of
crash data from 1997-2003 found ESC to be effective in reducing single-vehicle crashes,
including rollover. Among vehicles in the study, the results suggested that ESC reduced
single-vehicle crashes in passenger cars by 35% and in SUVs by 67%.
34. A later peer-reviewed study of ESC effectiveness found that ESC reduced single-vehicle
crashes in passenger cars by 34% and in SUVs by 59%, and that its effectiveness was
greatest in reducing single-vehicle crashes resulting in rollover (71% reduction for
passenger cars and an 84% reduction for SUVs). It also found reductions in fatal
single-vehicle crashes and fatal single-vehicle rollover crashes that were commensurate
with the overall crash reductions cited. ESC reduced fatal single-vehicle crashes in
passenger cars by 35% and in SUVs by 67% and reduced fatal single-vehicle crashes
involving rollover by 69% in passenger cars and 88% in SUVs.
5. INPUT ON THE SUBSTANCE OF THE ESC GTR
35. The substantive content of this global technical regulation for ESC was developed with the
input of a variety of interested parties, including the Contracting Parties to the 1998
Agreement, other governmental representatives, automobile manufacturers and trade
associations, the automobile equipment trade association, and safety advocacy
organizations. In addition, international automobile manufacturers conducted testing with a
broad array of ESC-equipped vehicles in order to assess potential performance criteria for
evaluating ESC systems. Thus, the ESC gtr has undergone a thorough vetting by not only
government regulators from the Contracting Parties, but also from the automotive industry
and the safety community.
36. The overwhelming majority of these participants supported establishing a technical
regulation for ESC systems installed on new light vehicles. Indeed, the difference of opinion
among the participants involved the stringency of the standard and the test procedures.
Other topics included making the "ESC System" definition more performance-based, lateral
responsiveness criteria, ESC performance requirements, ESC malfunction detection
requirements, ESC tell-tale requirements, system disablement and the "ESC Off" switch,
test procedures, and impacts on the aftermarket, among other things. In discussing the
provisions set forth as part of this gtr, this document addresses the issues raised by these
participants and the positions expressed on these topics.
43. One of the key elements of the gtr is the definition of "Electronic Stability Control System".
The definitional requirements specify the necessary elements of a stability control system
that is capable of both effective oversteer and understeer intervention. These requirements
are necessary due to the extreme difficulty in establishing tests adequate, by themselves, to
ensure the desired level of ESC functionality in a variety of circumstances. The test that
is being adopted is necessary to ensure that the ESC system is robust and meets a level of
performance at least comparable to that of current production ESC systems.
The ESC system shall meet additional specific functional requirements besides the
definition, as follows:
Be capable of applying braking torques individually to all four wheels
and have a
control algorithm that utilizes this capability;
Be operational over the full speed range of the vehicle, during all phases of driving
including acceleration, coasting, and deceleration (including braking), except:
a. When the driver has disabled ESC;
b. When the vehicle speed is below 20 km/h;
c. While the initial start-up self-test and plausibility checks are completed, not to
exceed 2 minutes when driven under the conditions of Paragraph 7.10.2.; and
d. When the vehicle is being driven in reverse.
Remain capable of activation even if the antilock brake system or traction control
system is also activated.
45. The gtr also specifies a number of other definitions intended to clarify the operation of ESC
systems or related performance testing. Specifically, definitions are provided for the
following terms: (1) "Ackerman Steer Angle"; (2) "Lateral Acceleration"; (3) "Oversteer"; (4)
"Sideslip or side slip angle"; (5) "Understeer"; (6) "Yaw rate"; and "SSF".
46. The gtr does not require the ESC system to be operable when the vehicle is being driven in
reverse, because such provision would necessitate costly changes to current ESC systems
with no anticipated safety benefit. The main safety problems associated with the vehicle
operating in reverse are backing into/over pedestrians, backing over edges (drop-offs), and
backing into inanimate objects (e.g., other vehicles, buildings). ESC is not expected to help
prevent any of these types of crashes. Furthermore, vehicles are rarely driven rapidly in
reverse, so the provision that ESC need not function when "the vehicle speed is below
20 km/h" means that ESC would typically not have to be active when the vehicle is in
47. The gtr acknowledges that the ESC system, the antilock brake system, and any traction
control system on current vehicles tend not to be functionally separate but instead to be
integrated into a single system, all of which utilize the vehicle's brake control system to
accomplish their intended stability enhancement goals. In order to allow subsystem
arbitration to occur as needed to optimize ESC performance, the regulation makes clear that
the vehicle's design logic for activation of these systems may be integrated so that these
systems can work in unison to address vehicle instabilities.
52. Furthermore, it is possible for a vehicle without ESC to be optimized to avoid spin-out in the
narrowly defined conditions of the ESC oversteer intervention test (especially if the
regulation is silent on understeer) but to lack the advantages of ESC under other conditions.
It has been determined that it is not currently feasible to develop a comprehensive battery of
tests that could substitute for the knowledge of what equipment constitutes ESC, and it
remains to be seen if such an approach would ever be practical to set a purely
performance-based standard that would ensure that manufacturers provide at least current
ESC systems. Therefore, the gtr's definition of "ESC System" is necessary in order to
ensure that vehicles subject to this regulation have the attributes of ESC systems that
produced the large reduction of single-vehicle crashes and rollovers in recent crash data
studies. The following discussion explains the identified obstacles to a strictly
53. Among the challenges associated with developing a performance test for ESC, it should be
noted that manufacturers develop ESC algorithms using tests whose conditions are
generally not repeatable (e.g., icy surfaces which change by the minute, wet/slippery
surfaces which are not repeatable day-to-day) and through simulation. Manufacturers also
use hundreds of conditions requiring weeks of testing for a given vehicle. However, it is not
practicable to use these approaches as part of a safety regulation. In contrast, this gtr is
objective and is expected to generate repeatable results.
54. It is possible to overcome these limitations through the gtr's use of a definition of "ESC
System," which is based on a Society of Automotive Engineers definition of what ESC is,
and which includes those elements that account for the cost of those systems. There is no
reason to believe that manufacturers will incur all the costs of the ESC equipment and
capabilities required by the regulation's definition and then just program the system to
achieve limited operation restricted to the test conditions of the gtr. The regulation's
definitional requirement for "ESC System" requires, at a minimum, the equipment and
capabilities of existing ESC system designs. This translates into the substantial fatality and
injury benefits provided by existing ESC systems.
55. Without the definition of "ESC System," it would not be feasible to assess comprehensively
the operating range of resulting devices, particularly for understeer intervention, that might
be installed in compliance with the safety standards. If manufacturers were to optimize the
vehicle so as to pass only a few highly-defined tests, the public would not receive the full
safety benefits provided by current ESC systems.
59. Furthermore, all of these other ESC-related components (including roll stability control )
lack supporting data to assess their effectiveness and to determine whether such
technologies meet the need for safety. The commonality of design for ESC systems in the
studies used to develop this regulation focused on individual brake application and engine
control, and at least one industry association (the 'Verband der Automobilindustrie') stated
that the definition for "ESC system" captures the state-of-the-art. Again, even though
certain later ESC designs incorporate some additional features, it was not possible to
determine the safety benefits, if any, of these features because these features were not
available on any of the ESC-equipped vehicles in the crash data study. Also, some of those
features are directed at comfort and convenience rather than safety.
60. Based upon the above consideration, it was concluded that there is no good reason to
postpone the proven life-saving benefits of basic ESC systems until such time as necessary
research could be conducted to assess the panoply of related components. Thus, instead
of specifying additional components as part of the regulation's definition for "ESC system," it
is left to the discretion of vehicle manufacturers to tailor the features of their individual ESC
systems to the needs of a given vehicle. The gtr does not limit manufacturers' ability to
develop, install, and advertise stability control systems that go beyond its requirements.
61. It is acknowledged that in requiring ESC as it now exists and has proven to be beneficial,
the gtr may be indirectly impacting hypothetical future technological innovations. Should
new advances lead to forms of ESC different than those currently required by this
regulation, Contracting Parties may seek to modify this gtr. It is also noted that the vehicle
manufacturers who are the directly regulated parties have not opposed using the definition
for "ESC System" as the primary requirement of the gtr, and some have actively supported
66. Specifically, the ESC malfunction tell-tale shall be mounted inside the occupant
compartment in front of and in clear view of the driver and be identified by the symbol shown
for "ESC Malfunction Tell-tale" as described in this regulation. The ESC malfunction tell-tale
shall remain continuously illuminated under the conditions specified in the regulation for as
long as the malfunction(s) exists, whenever the ignition locking system is in the "On" ("Run")
position, and except as otherwise provided, each ESC malfunction tell-tale shall be
activated as a check of lamp function either when the ignition locking system is turned to the
"On" ("Run") position when the engine is not running, or when the ignition locking system is
in a position between "On" ("Run") and "Start" that is designated by the manufacturer as a
check position. The ESC malfunction tell-tale need not be activated when a starter interlock
is in operation. The ESC malfunction tell-tale shall extinguish after the malfunction has
been corrected. Manufacturers may use the ESC malfunction tell-tale in a flashing mode to
indicate ESC operation.
a. Types of Malfunctions to be detected
67. Regarding the issue of which vehicle components are subject to ESC malfunction testing, a
rule of reason applies. Simply stated, if a vehicle malfunction was to affect the generation or
transmission of control or response signals in the vehicle's electronic stability control
system, it shall be detectable by the ESC system. In other words, if the malfunction impacts
the functionality of the ESC system, the ESC system shall be capable of detecting it. For
shared or connected components, a malfunction need only be detected to the extent it may
impact the ESC system's operation. Manufacturers are in the best position to know the
vehicle components involved in ESC operation.
b. Practicability Issues with ESC Malfunction Detection
68. The regulation specifies that disconnections and connections of ESC components are to be
made with the power turned off, in order to prevent the risk of harm to technicians.
69. The gtr intends to ensure that ESC malfunctions are detected within a reasonable time after
the start of driving. The language adopted specifically provides that the vehicle should be
driven during the proposed two-minute period so that the parts of its malfunction detection
capability which depend on vehicle motion can operate.
70. Furthermore, in response to industry input, the gtr clarifies that the ESC system is not
expected to maintain its monitoring capability with ignition turned off and that it is not
necessary to restrict the extinguishment of the tell-tale to the exact instant of the initiation of
the next ignition cycle.
75. Vehicle manufacturers are permitted to use the ESC malfunction tell-tale in a flashing mode
to indicate operation of the ESC system.
b. Tell-tale Labelling
76. In terms of how to label the ESC malfunction tell-tale, it is the gtr's intention to provide
flexibility to vehicle manufacturers via alternative text terms for tell-tales, while at the same
time promoting consistency of message. As the concept of ESC becomes more widely
understood by drivers, it is expected that offering the option of using the text term "ESC," as
opposed to manufacturer-specific ESC system acronyms, will facilitate driver recognition of
the tell-tale. Therefore, the regulation permits use of the term "ESC" at the manufacturer's
discretion instead of the ISO symbol.
77. In light of the importance of promoting drivers' understanding of ESC and whether or not
their vehicle is equipped with ESC, industry recommended combining the ISO symbol with
the acronym "ESC". Insofar as drivers will have to learn the precise meaning of any tell-tale
offered by manufacturers to convey the idea of ESC, it is not necessary at this time to
specifically require a tell-tale that includes both the symbol and the acronym, and there is no
evidence that both together will convey a greater benefit than either alone. It is expected
that most drivers become increasingly familiar with the meaning of instrument panel
tell-tales over time, and that the ESC malfunction tell-tale symbol and substitute "ESC" text
can effectively be used interchangeably. However, given vehicle manufacturers' stated
concern that limited instrument panel area is available for locating tell-tales, it is noted that it
is permissible to augment the ISO symbol with the text "ESC".
c. Use of Message Centers
78. It should be noted that in the event that the text alternative for the ESC malfunction tell-tale
is presented via the vehicle's message/information centre (sometimes referred to as a
"common space"), the regulation's tell-tale requirements shall continue to be met and the
warning shall not be displaced by a subsequent warning until such time as the malfunction
condition has been corrected.
d. Colour Requirement
79. The use of message/information centres for presentation of ESC malfunction information is
permissible to the extent that the relevant requirements of the regulation are met, including
the yellow colour requirement. The intent of the colour requirement is that the colour yellow
be used to communicate to the driver a condition of compromised performance of a vehicle
system that does not require immediate correction. The International Standards
Organization in its standard titled, "Road Vehicles − Symbols for controls, indicators, and
tell-tales" (ISO 2575:2004(E)), agrees with this practice through its statement of the
meaning of the colour yellow as "yellow or amber: caution, outside normal operating limits,
vehicle system malfunction, damage to vehicle likely, or other condition which may produce
hazard in the longer term". In the context of ESC, a yellow, cautionary warning to the driver
was purposely chosen to indicate an ESC system malfunction. This requirement shall be
maintained in order to communicate properly the level of urgency with which the driver shall
seek to remedy the malfunction of this important safety system.
84. If the vehicle manufacturer chooses this option, it shall also provide an "ESC Off" control
and a tell-tale that is mounted inside the occupant compartment in front of and in clear view
of the driver. The purpose of this tell-tale is to indicate to the driver that the vehicle has
been put into a mode that renders it unable to satisfy the requirements of the gtr. The ESC
Off tell-tale shall be identified by the following symbol (the ISO symbol J.14 with the English
word "OFF") or text:
SYMBOL WORD OR ABBREVIATION CONTROL COLOUR
85. Such tell-tale shall remain continuously illuminated for as long as the ESC is in a mode that
renders it unable to meet the performance requirements of the gtr, whenever the ignition
locking system is in the "On" ("Run") position. Except as provided in this regulation, each
"ESC Off" tell-tale shall be activated as a check of lamp function either when the ignition
locking system is turned to the "On" ("Run") position when the engine is not running, or
when the ignition locking system is in a position between "On" ("Run") and "Start" that is
designated by the manufacturer as a check position. The "ESC Off" tell-tale need not be
activated when a starter interlock is in operation. The "ESC Off" tell-tale shall extinguish
after the ESC system has been returned to its fully functional default mode.
86. Several participants raised specific issues pertaining to the ESC Off control and tell-tale,
which are set forth and addressed below.
h. System Disablement and the "ESC Off" Control
87. Most participants expressed support for the decision to permit vehicle manufacturers to
install ESC Off controls, stating that a driver may need to disable the ESC system in certain
situations such as when a vehicle is stuck in a deformable surface such as mud or snow, or
when a compact spare tyre, tyres of mismatched sizes, or tyres with chains are installed on
88. In contrast, some safety advocacy organizations have expressed concern that ESC on-off
controls may place motorists at unnecessary risk, particularly where de-activation occurs for
"driving enjoyment" or racing purposes; this small minority of drivers could disable their ESC
systems by other (unspecified) means. Concern was expressed that permitting ESC
disablement could result in the loss of benefits of an active ESC system for long distances
or considerable periods of time until the start of the next ignition cycle and that turning off
the ESC system could also disable ABS operation, thereby negatively impacting vehicle
safety. Alternatively, it was suggested that it may be unnecessary to permit ESC deactivation,
if ESC systems can operate in conjunction with vehicle traction control systems
or that the gtr permits ESC disablement controls, de-activation should require either: (1) a
long control engagement period, or (2) sequential control engagement actions.
89. After considering these observations, it was nevertheless decided that provision in the gtr
for a control to disable the ESC system temporarily will enhance safety. The rationale for
this position is detailed below.
j. ESC Operation After Malfunction and "ESC Off" Control Override
95. In discussions, concern was expressed that when an ESC malfunction is detected, some
drivers may respond by pressing the ESC Off control (if one is provided). However, not all
ESC malfunctions may render the system totally inoperable, so there may be benefits to
ensuring that the system remains active in those cases. Thus, it was suggested that
manufacturers should be permitted to disable the "ESC Off" control in those instances
where an ESC malfunction has been indicated or override the "ESC Off" control in other
appropriate situations. It was argued that at such times, the benefits of ESC operational
availability are more important than the ability to disable the system, and it was further
argued that because the "ESC Off" control is permitted at the vehicle manufacturer's option,
the manufacturer should be accorded discretion to appropriately limit the operation of that
96. It is logical to conclude that just because the manufacturer permits the ESC system to be
disabled under some circumstances, that does not mean that the manufacturer shall allow it
to be disabled at all times. If the vehicle manufacturer believes a situation has occurred in
which it should not be possible to turn ESC off, then the manufacturer should be permitted
to override the operation of the "ESC Off" control. The example of an ESC system
malfunction after which the driver triggers the "ESC Off" control is illustrative of such a
situation; in such cases, the vehicle operator presumably had desired to maintain ESC
functionality while driving, so the driver's action to turn the system off arguably reflects a
reflex reaction that the system is unavailable and shall be shut down, rather than a
reasoned decision to forgo any residual ESC benefits that might remain in spite of the
malfunction. Similarly, it makes little sense to require the ESC system to remain disabled if
the vehicle manufacturer believes a situation has occurred in which ESC should again
become functional. The gtr's regulatory text has been drafted in a manner which reflects
k. Default to "ESC On" Status
97. This gtr recognizes that there may be certain situations in which ESC disablement may be
appropriate (e.g., vehicles stuck in snow or mud), but considered the fact that permitting the
ESC system to remain disabled until the next ignition cycle (i.e. default mode upon vehicle
start-up be ESC "full-on") could be problematic. It was argued that the driver may
inadvertently forget to reengage the ESC for the remainder of the current trip by turning the
ignition off and then on again, and that waiting for the next ignition cycle to require
reengagement of the ESC system needlessly compromises potential safety benefits. One
suggestion was to have the gtr require that, once disabled, the ESC system shall again
become operational when the vehicle reaches a speed of 40 km/h (or develop some other
alternative, such as a time-delay reminder to re-enable the system or some other means of
98. In response, it is noted that although ESC systems shall always return to the manufacturer's
original default mode that satisfies the regulatory requirements at the initiation of each new
ignition cycle, manufacturers have the freedom to equip their vehicles with ESC systems
that return to a compliant mode sooner, based upon an automatic speed trigger or timeout.
m. Labelling of the "ESC Off" Control
101. Industry stakeholders agreed that the "ESC Off" control should be identified, but they
argued that vehicle manufacturers should be granted flexibility in terms of how to identify the
"ESC Off" control. The industry stated that it is not necessary to standardize the
identification of the control because vehicle manufacturers have been providing drivers with
more detailed feedback on the ESC operating mode when the system is in other than the
default "full on" mode. In other words, the argument is that because vehicle manufacturers
are providing a tell-tale that would illuminate whenever the system is in a mode other than
"full on," they should be permitted discretion to optimize control labelling in ways that would
facilitate driver understanding of variable ESC modes (i.e. permitting an identification other
than "ESC Off").
102. There is a legitimate concern for ensuring driver understanding of ESC status. Therefore, it
would be beneficial to encourage drivers to select ESC modes other than "full on" only when
driving conditions warrant. However, standardized control labelling of an "ESC Off" control
shall be maintained, and, therefore, manufacturers shall identify an actual "ESC Off" control
using the specified "ESC Off" symbol or "ESC Off" text (which may be supplemented with
other text and symbols). However, there is a difference between a dedicated "ESC Off"
control (i.e. one whose sole function is to put the ESC system in a mode in which it no
longer satisfies the requirements of an ESC system, and which accordingly shall bear the
required "ESC Off" labelling) and other types of controls.
103. One type of control to be clarified as excluded is one which has a different primary purpose
(e.g., a control for the selection of low-range 4WD that locks the axles), but which shall turn
off the ESC system as an ancillary consequence of an operational conflict with the function
that it controls. In this case, such a control would be made confusing by adding "ESC Off"
to its functional label. Nevertheless, in such situations, the "ESC Off" tell-tale shall
illuminate to inform the driver of ESC system status.
104. Another type of control to be clarified as excluded is one that changes the mode of ESC to a
less aggressive mode than the default mode but which still satisfies the performance criteria
of this gtr. In such cases, the manufacturer may label such a control with an identifier other
than "ESC Off," and the manufacturer is permitted, but not required, to use the "ESC Off"
tell-tale beyond the default mode to signify lesser modes that still satisfy the test criteria. If
this control is combined with a control that puts ESC in a mode in which it no longer satisfies
the test criteria (a "dedicated" ESC Off control), as on a multi-mode switch or button, the
multi-mode control shall be labelled with either the words "ESC OFF" or the symbol word
combination for "ESC Off".
n. Location of the "ESC Off" Control
105. Certain industry participants requested that vehicle manufacturers be provided flexibility in
the placement of the ESC Off control for the following reasons. First, it was argued that the
ESC Off control would be infrequently used during normal driving. Second, it was argued
that the location of the ESC Off control would help ensure that disabling of the ESC reflects
a deliberate act by the driver.
106. For the reasons that follow, the "ESC Off" control location shall be visible to and operable by
the driver while properly restrained by the seat belt. Hand-operated controls should be
mounted where they are easily visible to the driver so as to minimize visual search time,
because safety may be diminished the longer a driver's vision and attention are diverted
from the roadway. Furthermore, relative consistency of location across vehicle platforms
will promote easy identification of the control when drivers encounter a new vehicle.
112. The regulation provides that the ESC malfunction tell-tale shall be illuminated "…after the
occurrence of any malfunction". Manual disablement of the ESC by the driver does not
constitute an ESC malfunction. In order to prevent confusion on the part of the driver, it has
been decided that the ESC malfunction tell-tale can only be used when a malfunction exists.
Specifically, if the ESC malfunction tell-tale were permitted to be presented simultaneously
with the "ESC Off" tell-tale, drivers would be unable to distinguish whether the system had
been switched off or whether a malfunction had occurred. Therefore, presentation of the
ESC malfunction tell-tale in addition to an "ESC OFF" indication when ESC has been
disabled via the driver-selectable control and no system malfunction exists is prohibited.
t. Use of Two-Part Tell-tales
113. Some industry stakeholders stated that vehicle manufacturers should be permitted the
flexibility to use two adjacent tell-tales, one containing the ISO symbol for the proposed
yellow ESC malfunction indicator and another yellow tell-tale with the word "Off". It was
argued that, given the limited space available on vehicle instrument clusters, this
dual-purpose combination would increase efficiency by allowing one lamp to be illuminated
to indicate ESC malfunction and both to be illuminated to indicate that the system has been
turned off or placed in a mode other than the "full on" mode.
114. This gtr would permit the tell-tale configuration described above. Indication of a malfunction
condition generally shall always be the predominant visual indication provided to the driver
by a tell-tale. As a result, if a two-part ESC tell-tale was used and an ESC malfunction
occurred, only the malfunction portion of the tell-tale could be illuminated. However, other
provisions in the regulation state that a tell-tale consisting of the symbol for "ESC Off" or
substitute text shall be illuminated when a control input to the ESC switch (i.e. control) has
been made by the driver to put the vehicle into a non-compliant mode. Thus, both parts of
the two-part tell-tale would be required to illuminate. In the rare event that an ESC
malfunction occurs while the ESC has been manually disabled, this gtr would allow the ESC
Off message to remain (i.e. both parts of the two-part tell-tale to remain illuminated) until the
next ignition cycle (at which point the ESC shall revert to "full on" mode regardless), at
which point the ESC malfunction part of the two-part tell-tale shall be illuminated.
u. Conditions for Illumination of the "ESC Off" Tell-tale: Speed
115. The automobile industry sought clarification that the "ESC Off" tell-tale (if an "ESC Off"
control is provided) need not illuminate when the vehicle is travelling below the low-speed
threshold at which the ESC system becomes operational. That understanding is correct.
The regulation requires that the ESC system shall be "…operational during all phases of
driving including acceleration, coasting, and deceleration (including braking), except when
the driver has disabled ESC or when the vehicle is below a speed threshold where loss of
control is unlikely". Thus, the ESC system need not be functional when the vehicle is
travelling at a speed below the low-speed threshold. Furthermore, the regulation requires
the vehicle manufacturer to illuminate the "ESC Off" tell-tale when the vehicle has been put
into a mode that renders it unable to satisfy the gtr's performance requirements. Driving a
vehicle at low speeds does not equate with the vehicle operator actively using a
driver-selectable control that places the ESC system into a mode in which it will not satisfy
these performance requirements. Therefore, the regulation should not be read to imply that
the "ESC Off" tell-tale shall be illuminated when the vehicle is travelling at low speeds, and it
is sufficiently clear in defining the conditions under which the "ESC Off" tell-tale shall be
121. However, the safety need for an ESC activation indicator to alert the driver during an
emergency situation that ESC is intervening is not obvious. It would seem that with ESC, as
with anti-lock brake systems, vehicle stability would be increased regardless of whether
feedback was provided to inform the driver that a safety system had intervened. No data
have been provided to suggest that safety benefits are enhanced by alerting the driver of
ESC activations. Nevertheless, current research on the topic of ESC activation warnings
supports this gtr's current approach that an ESC activation indication should neither be
prohibited nor required, as explained below.
122. The results of recent research neither show that alerting a driver to ESC activation provides
a safety benefit, nor that it may prove to be a source of distraction that could lead to adverse
safety consequences. Research shows that drivers presented with the flashing tell-tale
were more likely to glance at the instrument panel and that these drivers typically glanced at
the panel twice, rather than just once as for the steady-burning tell-tale or no tell-tale.
Insofar as a flashing tell-tale draws a driver's attention away from the road, where it should
be during an emergency loss-of-control situation, requiring it is not logical. It makes sense
to alert drivers to slick road conditions, when the driver is operating the vehicle on the
roadway in a generally straight path, but it would not make sense to draw the driver's
attention away from the road when they are in the midst of assessing a crash-imminent
situation and attempting to avoid a collision.
123. While research to date shows that drivers looked at a flashing tell-tale twice as often, this
did not result in significantly different rates for loss of control, road departures, and collisions
than with steady-burning tell-tales or no tell-tales. Thus, despite the logical risk of looking
away from the road during an ESC-worthy manoeuvre, there is no apparent detriment from
the increased glances at a flashing tell-tale. Currently available research results are
insufficient to support prohibition of the existing practice of providing a visual indication of
ESC activation, but neither do they support requiring it.
124. Once additional data from relevant research become available and are analyzed, it may be
possible to clarify further which strategy for notifying the driver of ESC activation is least
likely to negatively impact the driver's response to a loss-of-control situation. However,
unless additional research provides strong, statistically-valid evidence of a benefit or
detriment associated with presentation of an ESC activation indication, no requirement or
prohibition for such an indication will be made.
125. Consistent with available research, auditory indications of ESC activation are not necessary
and provide no apparent safety benefit. However, while research suggests that an auditory
indication of ESC activation elicits longer instrument panel glances and may be associated
with an increase in road departures, it is not considered that these results from a single
simulator study provide sufficient justification to prohibit use of an auditory ESC indicator.
Therefore, while an auditory ESC activation warning would be discouraged, even when
combined with a visual indication, current data do not justify a prohibition of such approach.
x. Flashing Tell-tale as Indication of Intervention by Related Systems/Functions
126. The automobile industry requested that it be permitted to flash the ESC malfunction tell-tale
to indicate the intervention of other related systems, including traction control and trailer
stability assist function. The industry reasoned that these functions are directly related to
the ESC system and that the driver would experience the same sensations from the braking
system actuator and throttle control triggered by operation of these related systems, as they
would in the event of ESC activation. In addition to keeping the driver informed, it also
reasoned that this strategy would aid in minimizing the number of tell-tales used for related
133. ESC-equipped vehicles covered under this gtr are also required to meet performance tests.
Specifically, such vehicles shall satisfy the gtr's stability criteria and responsiveness criteria
when subjected to the Sine with Dwell steering manoeuvre test. This test involves a vehicle
coasting at an initial speed of 80 km/h while a steering machine steers the vehicle with a
steering wheel pattern as shown in Figure 2 of the regulatory text. The test manoeuvre is
then repeated over a series of increasing maximum steering angles. This test manoeuvre
was selected over a number of other alternatives, because it was decided that it has the
most optimal set of characteristics, including severity of the test, repeatability and
reproducibility of results, and the ability to address lateral stability and responsiveness.
134. The manoeuvre is severe enough to produce spinout for most vehicles without ESC. The
stability criterion for the test measure is how quickly the vehicle stops turning after the
steering wheel is returned to the straight-ahead position. A vehicle that continues to turn for
an extended period after the driver steers straight is out of control, which is what ESC is
designed to prevent.
Lateral Stability Criterion
135. The quantitative stability criteria are expressed in terms of the per cent of the peak yaw rate
after maximum steering that persists at a period of time after the steering wheel has been
returned to straight ahead. The criteria require that the vehicle yaw rate decrease to no
more than 35% of the peak value after one second and that it continues to drop to no more
than 20% after 1.75 seconds.
Lateral Responsiveness Criterion
136. Since a vehicle that simply responds very little to steering commands could meet the
stability criteria, a minimum responsiveness criterion is applied to the same test. It requires
that an ESC-equipped vehicle with a GVM of 3,500 kg or less shall move laterally at least
1.83 m during the first 1.07 seconds after the Beginning of Steer (BOS); (Initiation of
steering marks a discontinuity in the steering pattern that is a convenient point for timing a
measurement. BOS is defined in the regulation at Paragraph 7.11.6.). It also requires that
a heavier vehicle with a GVM greater than 3,500 kg shall move at least 1.52 m laterally in
the same manoeuvre for specified steering angles (i.e. conducted with a commanded
steering wheel angle of 5A or greater). These computations are for the lateral displacement
of the vehicle centre of gravity with respect to its initial straight path.
140. However, even a robust steering machine cannot maintain the commanded steering profile
with some vehicle power steering systems. Some of the electric power steering systems
are especially marginal in that their power assistance diminishes at high steering wheel
velocities. In the case of vehicle power steering limitations, the first steering angle peak in
Figure 2 cannot be met, but the second peak as well as the frequency of the wave form are
usually achieved. Thus, marginal vehicle power steering does not likely reduce the severity
of the oversteer intervention part of the test, but it will reduce the steering input that helps
the vehicle satisfy the responsiveness criteria. If the regulation were to use the actual
steering angle rather than the commanded steering angle as the normalized steering angle
for the responsiveness test, it could create the unacceptable situation of vehicles that could
not be tested for compliance, because the test would not allow for their evaluation. For
example, if the steering machine could not achieve a normalized steering wheel angle of
5.0 even when commanded to a normalized angle of 6.5 because of vehicle limitations, the
vehicle could not be said to fail, no matter how poor its performance.
141. Therefore, the gtr uses the commanded steering profile (using an assuredly robust steering
machine), rather than the measured steering profile, to calculate the normalized steering
wheel angle used to assess compliance with our lateral displacement requirement. This
should not create a practical problem. At this time, the larger vehicles have reasonably
powerful steering systems that should enable them to achieve actual peak steering angles
within at least 10° of the commanded peak. Furthermore, under this approach to defining
the steering input, the lateral displacement required for large vehicles would be reduced to
1.52 m rather than the 1.68 m requested by the industry (with its somewhat higher
measured steering angle). The weaker electric power steering systems discussed above
are typically found on cars, and cars tend to be responsive enough to pass the 1.83 m
lateral displacement criterion at normalized steering wheel angles of less than 5.0.
142. As noted above, the gtr includes a responsiveness criterion that specifies a minimum lateral
movement of 1.83 m during the first 1.07 seconds of steering during the Sine with Dwell
manoeuvre. The purpose of the criterion is to limit the loss of responsiveness that could
occur with unnecessarily aggressive roll stability measures incorporated into the ESC
systems of SUVs. This is a real concern, as research has demonstrated that one such
system reduced the lateral displacement capability of a mid-sized SUV below that attainable
with a 15-passenger van, multiple unloaded long wheelbase diesel pickups, and even a
stretched wheelbase limousine.
143. A heavy-duty pickup truck understeers strongly in this test because of its long wheelbase
and because it is so front-heavy under the test condition. The ESC standard is not intended
to influence the inherent chassis properties of these vehicles (which were tested without
ESC), because low responsiveness in the unloaded state is the consequence of a chassis
with reasonable inherent stability in the loaded state. The gtr shall avoid causing any
vehicle to be designed with a chassis that is unstable at GVM and relies on ESC in normal
operation. In addition, some very large vans with a high centre of gravity, such as
15-passenger vans, rely on their ESC system to reduce responsiveness because of special
concerns for loss of control and rollover. While it is necessary to respect the
responsiveness limitations appropriate to large vehicles with commercial purposes, there is
no need for lighter vehicles designed for personal transportation, including SUVs, to give up
so much of the object avoidance capability of their chassis when tuning the ESC system.
The Issue of Understeer Performance
148. The following discussion explains the concept of vehicle understeer, how ESC systems
operate to control excessive understeer, and why it was not possible to develop and
incorporate an understeer performance test as part of this gtr.
149. As background, all light vehicles (including passenger cars, pickups, vans, minivans,
crossovers, and sport utility vehicles) are designed to understeer in the linear range of
lateral acceleration, although operational factors such as loading, tyre inflation pressure,
and so forth can in rare situations make them oversteer in use. This is a fundamental
design characteristic. Understeer provides a valuable, and benign, way for the vehicle to
inform the driver of how the available roadway friction is being utilized, insofar as the driver
can 'feel' the response of the vehicle to the road as the driver turns the steering wheel.
Multiple tests have been developed to quantify linear-range understeer objectively, including
SAE J266, "Steady-State Directional Control Test Procedures for Passenger Cars and Light
Trucks," and ISO 4138, "Road vehicles − Steady state circular test procedure". These tests
help vehicle manufacturers design their vehicles with an appropriate amount of understeer
for normal linear-range driving conditions. Tests such SAE J266 and ISO 4138 simply
measure the small constant reduction in vehicle turning (in comparison to the geometric
ideal for a given steering angle and wheelbase) that characterizes linear range understeer
at relatively low levels of lateral acceleration. This is much different from limit understeer in
loss-of-control situations where even large increases in steering to avoid an obstacle create
little or no effect on vehicle turning.
150. In the linear range of handling, ESC should never activate. ESC interventions occur when
the driver's intended path (calculated by the ESC control algorithms using a constant linear
range understeer gradient) differs from the actual path of the vehicle as measured by ESC
sensors. Since this does not occur while driving in the linear range, ESC intervention will
not occur. Therefore, ESC has no effect upon the linear-range understeer of a vehicle.
151. In overview, understeer intervention is one of the core functions of an ESC system, a
feature common to all current production systems. A literature search of the available
research was conducted in the U.S. in order to identify a potential ESC understeer test for
loss-of-control situations. However, no such tests were found. Understeer tests in the
literature (such as SAE J266 and ISO 4138) focus on linear range understeer properties and
are not relevant to the operation of ESC, as explained above.
152. Because there are no suitable tests of limit understeer performance in existence and
because of the complexity of undertaking new research in this area, several years of
additional work would be required before any conclusions could be reached regarding an
ESC understeer performance test. A principal complication is that manufacturers often
program ESC systems for SUVs to avoid understeer intervention altogether on dry roads
because of concern that the intervention could trigger tip-up or make the oversteer control of
some vehicles less certain in high-speed situations.
157. In sum, the above information would be expected to allow the Contracting Party to
understand the operation of the ESC system and to verify that the system has the
necessary hardware and logic for mitigating excessive understeer. This ensures that
vehicle manufacturers are required to provide understeer intervention as a feature of the
ESC systems, without delaying the life-saving benefits of the ESC gtr (including those
attributable to understeer intervention). In the meantime, the Contracting Parties will
monitor the progress of any additional research in the area of ESC understeer intervention
and consider taking further action, as appropriate.
158. It is further noted that the understeer requirement is objective, even without a specific
performance test. The definition of "ESC System" requires not only an understeer capability
(Part (2) of the definition), but also specific physical components that allow excessive
understeer mitigation (Part (1) of the definition).
Other Test Requirement Issues (Post Data Processing Calculations)
159. Participants raised numerous issues related to the appropriateness and technical details of
the ESC requirements and test procedures. These issues were carefully considered in
developing this gtr. Additional details regarding these issues are provided below.
a. Determining the Beginning of Steering
160. In order to ensure consistent calculation of lateral displacement, careful consideration was
given to the gtr's data processing specifications. One topic included determining the start of
steering, which the regulation ultimately defined as the moment when the "zeroed" steering
wheel angle (SWA) passes through 5°.
161. The process to identify "beginning of steering" uses three steps. In the first step, the time
when steering wheel velocity that exceeds 75 deg/sec is identified. From this point, steering
wheel velocity shall remain greater than 75 deg/sec for at least 200 ms. If the condition is
not met, the 200 ms validity check is applied the next time steering wheel velocity that
exceeds 75 deg/sec is identified. This iterative process continues until the conditions are
satisfied. In the second step, a zeroing range defined as the 1.0 second time period prior to
the instant the steering wheel velocity exceeds 75 deg/sec (i.e. the instant the steering
wheel velocity exceeds 75 deg/sec defines the end of the "zeroing range") is used to zero
steering wheel angle data. In the third step, the first instance the filtered and zeroed
steering wheel angle data reaches -5° (when the initial steering input is counter clockwise)
or +5° (when the initial steering input is clockwise) after the end of the zeroing range is
identified. The time identified in Step 3 is taken to be the beginning of steer.
162. It was decided that an unambiguous reference point to define the start of steering is
necessary in order to ensure consistency when computing the performance metrics
measured during testing. The practical problem is that typical "noise" in the steering
measurement channel causes continual small fluctuations of the signal about the zero point,
so departure from zero or very small steering angles does not indicate reliably that the
steering machine has started the test manoeuvre. Extensive evaluation of zeroing range
criteria (i.e. that based on the instant a steering wheel rate of 75 deg/sec occurs) has
confirmed that the method successfully and robustly distinguishes the initiation of the Sine
with Dwell steering inputs from the inherent noise present in the steering wheel angle data
channel. As such, the regulation incorporates the 75 deg/sec criterion described above plus
a 5° steering measurement. The value for time at the start of steering, used for calculating
the lateral responsiveness metrics, is interpolated.
a. Ambient Temperature Range
168. The regulation states that testing will be conducted when the ambient temperature is
between 0° C and 45° C. It was originally decided, based upon participant input, that the
temperature value should be 7° C. The reason is that research demonstrates that
responsiveness is reduced at higher temperatures, which is typical of vehicles with allseason
tyres. The temperature values reflect the general desirability of reducing sources of
variability in vehicle testing, in order to prevent testing at temperatures that favour a
vehicle's chance of passing the test. Higher minimum temperature values were considered
(e.g., 10° C), but such temperature has the disadvantage of reducing the length of the
testing season for potential test facilities in colder regions. Thus, the value selected reflects
the dual goals of better repeatability but also practicability. The following provides additional
detail on how these ambient temperature requirements were determined.
169. Industry participants stated that their analysis had demonstrated ESC test variability due to
temperature. It was suggested that, at near-freezing temperatures, certain high
performance tyres could enter their "glass transition range," which could introduce further
test variability. Accordingly, it was recommended that the lower bound of the temperature
range should be 10° C. In addition to reducing test variability, it was asserted that such an
approach to the temperature portion of the test procedures would permit virtually year-round
testing at many facilities, reduce burdens associated with confirming compliance at low
temperatures, and avoid complications of snow and ice during testing.
170. A vehicle's ESC system is designed for and expected to address stability issues over a wide
range of various environmental conditions. Testing conducted indicates that lateral
displacement for vehicles equipped with all-season tyres varies with fluctuating ambient
temperatures. According to the industry, the data indicate that lateral displacement for test
vehicles equipped with all-season tyres increases as the ambient temperature decreases,
suggesting that the displacement requirement could be met more easily at lower ambient
temperatures. However, this same relationship was not manifested in test vehicles
equipped with high performance tyres (some high-performance tyres are not designed for
operation under freezing conditions, and the performance variability of these tyres under
cold ambient temperatures is unknown, because in repeatability studies considered, tyres
are tested in the temperature ranges in which they are designed to operate). The industry
recommended minimizing potential test variability by reducing the specified test condition
ambient temperature range. To minimize test variability, the lower bound of the temperature
range was set for ESC testing to 7° C. It was believed that 7° C is appropriate because it is
low enough to increase the length of the testing season at multiple testing sites, and also
represents the low end of the relevant temperature range for some brands of high
performance tyres. However, because certain Contracting Parties requested a lower bound
of the temperature range of 0° C and because there may be certain tyre/vehicle
combinations that perform acceptably under such conditions, this gtr will allow testing down
to 0° C.
a. Vehicle Test Mass
177. In the test procedures, the gtr specifies that the vehicle is loaded with the fuel tank filled to
at least 90% of capacity, and total interior load of 168 kg comprised of the test driver,
approximately 59 kg of test equipment (automated steering machine, data acquisition
system and power supply for the steering machine), and ballast as required by differences
in the mass of test drivers and test equipment. Where required, ballast shall be placed on
the floor behind the passenger front seat or if necessary in the front passenger foot well
area. All ballast shall be secured in a way that prevents it from becoming dislodged during
178. Given that the mass of a 95 percentile male is 102 kg, it is believed that the maximum
allowable mass allocated for the test driver (109 kg) is conservative and should not impose
an unreasonable testing burden on parties performing ESC testing.
179. In the U.S., some participants recommended clarifying the location where ballast (if
required) is to be placed in the vehicle to account for varying mass of test drivers and test
equipment. As a result, specifications have been incorporated in the regulation as to where
the ballast shall be positioned. Such specification serves not only to ensure even
distribution of the load of the driver, steering machine, and test equipment, but it also
acknowledges the potential for the very abrupt vehicle motions imposed by the Sine with
Dwell manoeuvre to dislodge and/or relocate unsecured ballast during testing. Contracting
Parties may provide further direction in any accompanying laboratory test procedure, as
180. Industry participants conceded that the use of outriggers may be appropriate during testing,
but recommended that the regulation should explicitly clarify the vehicle class's properties
that are to be equipped with outriggers (e.g., trucks, multipurpose vehicles, and buses) and
set forth the design specifications for those devices. Concern was expressed that without
such clarification, outriggers can influence vehicle dynamics in the subject tests. Therefore,
in order to reduce test variability and increase the repeatability of test results, the gtr
specifies that outriggers may be used if deemed necessary for test driver safety. For
vehicles with a SSF less than or greater than 1.25, the gtr also specifies maximum mass
and roll moment of inertia specifications for outriggers.
Calculation of Lateral Displacement
187. One participant expressed concern with an ESC test procedure that would compute lateral
displacement by using double integration with respect to time of the measurement of lateral
acceleration at the vehicle centre of gravity (with time t=0 for the integration operation is the
instant of steering initiation), because it believes that the same vehicle, when tested at
different facilities and by different engineers, may experience differences in lateral
displacement of up to 60 cm. Specifically, it suggested that problems could arise from the
test procedures' computation of lateral displacement and also the repeatability of those
procedures. This participant also suggested that the test should be based upon "spin
velocity" rather than "spin displacement;" the reasoning was that this approach would render
timing less important, because spin velocity at 1.071 seconds is roughly constant, and it
argued that measurements of "spin velocity" would be easier to repeat.
188. Technically speaking, the lateral displacement evaluated under the regulation is not the
"lateral displacement of the vehicle's centre of gravity," but an approximation of this
displacement. In the present context, the location of the vehicle's centre of gravity
corresponds to the longitudinal centre of gravity, measured when the vehicle is at rest on a
flat, uniform surface. The lateral displacement metric, as defined, is based on the double
integration of accurate lateral acceleration data. Lateral acceleration data are collected from
an accelerometer, corrected for roll angle effects, and resolved to the vehicle's centre of
gravity using coordinate transformation equations. The use of accelerometers is
commonplace in the vehicle testing community, and installation is simple and well
understood. However, this gtr also permits use of GPS-based data for calculation of lateral
displacement if a Contracting Party determines that the GPS-based calculation method is
equivalent or better in accuracy than the double integration method.
191. However, studies have shown that human drivers can sustain handwheel rates of up to
1189° per second for 750 milliseconds, a steering rate which corresponds to a steering
angle magnitude of approximately 303°. It is conceded that the method used to
determine maximum Sine with Dwell steering angles can produce very large steering
angles. Of the 62 vehicles used to develop the Sine with Dwell performance criteria, the
vehicle requiring the most steering required a maximum steering angle of 371° (calculated
by multiplying the average steering angle capable of producing a lateral acceleration of
0.3 g in the Slowly Increasing Steer manoeuvre times a steering scalar of 6.5). Use of this
steering wheel angle required an effective steering wheel rate of 1454° per second, a
magnitude well beyond the steering capability of a human driver.
192. In order to ensure that the maximum steering angle in the regulation does not surpass the
steering capability of a human driver, the regulation provides that the steering amplitude of
the final run in each series is the greater of 6.5A or 270°, provided the calculated magnitude
of 6.5A is less than or equal to 300°. If any 0.5A increment, up to 6.5A, is greater than 300°,
the steering amplitude of the final run shall be 300°.
193. It was recommended that the gtr should include specifications for data filtering methods
directly in its regulatory text, given the potential for different filtering methods to significantly
influence final results. Specifically, the following filtering protocol was recommended for all
channels (except steering wheel angle and steering wheel velocity): (a) create a six-pole,
low-pass Butterworth filter with a 6 Hz cut-off frequency, and (b) filter the data forwards and
backwards so that no phase shift is induced. For the steering wheel angle channel, use of
the same protocol was recommended, but with a 10 Hz cut-off frequency. For steering
wheel velocity, adoption of a specific calculation was also recommended.
194. Data filtering methods can have a significant impact on final test results used for
determining vehicle compliance with this regulation, and the same filtering and processing
protocols shall be followed in order to ensure consistent and repeatable test results.
Accordingly, the test procedures section of the gtr's regulatory text now specifies critical test
filtering protocols and techniques to be used for test data processing.
195. Industry participants provided their assessment of the effect of brake pad temperatures on
ESC test results, particularly given the potential for drivers to use heavy braking between
test runs. Charts were provided based upon research that purported to demonstrate
variance in testing due to brake pad temperature, which would be an artefact of the test
methodology, not a reflection of expected ESC performance in the real world. Therefore, in
order to minimize non-representative test results, a recommendation was made that the
ESC test procedures should specify a minimum of 90 seconds between test runs in order to
allow sufficient time for cooling of the brake pads.
202. The responsiveness criteria proposed for use in this gtr, that a vehicle with a GVM of greater
than 3,500 kg shall achieve at least 1.83 m (1.52 feet) of lateral displacement when the Sine
with Dwell manoeuvre is performed with normalized steering angles greater than 5.0,
adequately safeguards against implementation of overly aggressive ESC systems, even
those specifically designed to mitigate on-road untripped rollover (i.e. systems that may
consider stability more important than path-following capability). Achieving acceptable
lateral stability is very important, but should not be accomplished by grossly diminishing a
driver's crash avoidance capability.
203. Intervention intrusiveness can refer to how the vehicle manufacturer and its ESC vendor
"tune" an ESC system for a particular vehicle make/model, specifically how apparent the
intervention is to the driver. It is not believed that it is appropriate to dictate this form of
intervention magnitude, as it can be an extremely subjective specification. As long as a
vehicle's ESC (1) satisfies the regulation's hardware and software definitions, and (2) allows
the vehicle to comply with the lateral stability and responsiveness performance criteria,
intervention intrusiveness should be a tuning characteristic best specified by the
204. In response to the issue of manoeuvre selection, twelve test manoeuvres were evaluated in
the U.S. before ultimately selecting the Sine with Dwell manoeuvre to assess ESC
performance. As explained below, this U.S. evaluation was performed in two stages, an
initial reduction from twelve manoeuvres to four, then from four to one.
205. The first stage began with identification of three important attributes: (1) high manoeuvre
severity ("manoeuvre severity"); (2) capability to produce highly repeatable and reproducible
results using inputs relevant to real-world driving scenarios ("face validity"); and (3) ability to
effectively evaluate both lateral stability and responsiveness ("performability"). To quantify
the extent to which each manoeuvre possessed these attributes, adjectival ratings ranging
from "Excellent" to "Fair" were assigned to each of the twelve manoeuvres, for each of the
three manoeuvre evaluation criteria. Of the twelve test manoeuvres, only four received
"Excellent" ratings for each of the manoeuvre evaluation criteria − the Increasing
Amplitude Sine (0.7 Hz), Sine with Dwell (0.7 Hz), Yaw Acceleration Steering Reversal
(YASR; 500 deg/sec), and Yaw Acceleration Steering Reversal with Pause (YASR with
Pause; 500 deg/sec steering rate).
206. Stage two of the manoeuvre reduction process used data from 24 vehicles (a sampling of
sports cars, sedans, minivans, small and large pickup trucks, and sport utility vehicles) to
compare the manoeuvre severity, face validity, and performability of the four manoeuvres
selected in the first stage. The ability of the four manoeuvres to satisfy these three
evaluation criteria were compared and rank ordered.
207. Of the four candidate manoeuvres, the Sine with Dwell and YASR with Pause were the top
performers in terms of evaluating the lateral stability component of ESC functionality.
However, due to the fact that the Sine with Dwell manoeuvre required smaller steering
angles to produce spinouts for five of the ten vehicles evaluated with left-right steering, and
for two of the ten vehicles with right-left steering (with the remaining thirteen tests using the
same steering angles), the Sine with Dwell manoeuvre was assigned a higher manoeuvre
severity ranking than that assigned to the YASR with Pause manoeuvre.
214. Note that all test track evaluations inherently contain some degree of output variability,
regardless of what aspect of vehicle performance they are being used to evaluate. In the
context of ESC testing, it is conceded that this variability could result in a marginally
non-compliant vehicle passing the test, but it is important to recognize these situations
would only affect a very small population of vehicles, and that the effect of instrumentation
and/or calculation errors is likewise believed to be very small. Since the performance of
most contemporary target vehicles resides far enough away from the regulation's
performance thresholds, it is extremely unlikely that measurement complications will be
solely responsible for having the performance of a non-compliant vehicle being deemed
Representativeness of Real World Conditions
215. A few participants in the U.S. questioned how many tests are necessary to ensure that the
ESC system is robust, and how many different configurations of tyres, loading, and trailering
are needed to be representative of real world driving. Concerns were also expressed that
even though an ESC system may increase safety under certain conditions, in other cases, it
may add unpredictable and unusual characteristics to the vehicle.
216. Many crash data studies quantifying real world ESC effectiveness were reviewed.
Regardless of the origin of the data used for these studies (i.e. whether from France,
Germany, Japan, Sweden, the United States, etc.), all reported or estimated that ESC
systems provide substantial benefits in "loss of control" situations. These studies reported
that ESC is expected to be particularly effective in situations involving excessive oversteer,
such as "fishtailing" or "spinout" which may result from sudden collision avoidance
manoeuvres (e.g., lane changes or off-road recovery manoeuvres).
217. The Sine with Dwell manoeuvre is specifically designed to excite an oversteer response
from the vehicle being evaluated. While this manoeuvre has been optimized for the test
track (because objectivity, repeatability, and reproducibility are necessary elements of a
regulatory compliance test), it is important to recognize that multiple studies have indicated
that the steering angles and rates associated with the Sine with Dwell manoeuvre are within
the capabilities of actual drivers, not just highly trained professional test drivers.
218. It is noted that there is no evidence of any "unpredictable and unusual characteristics"
imparted by any ESC system on the vehicle in which it is installed. ESC interventions occur
in extreme driving situations where the driver risks losing control of the vehicle, not during
"normal" day-to-day driving comprised of relatively small, slow, and deliberate steering
inputs. In these extreme situations, the driver shall still operate the vehicle by conventional
means (i.e. use of steering and/or brake inputs are still required to direct the vehicle where
the driver wants it to go); however, the mitigation strategies used by ESC to suppress
excessive oversteer and understeer help improve the driver's ability to successfully retain
control of the vehicle under a broad range of operating conditions.
224. It is anticipated that, when all U.S. light vehicles are equipped with ESC, the regulation
would prevent 67,466 to 90,807 crashes (1,430 to 2,354 fatal crashes and 66,036 to 88,453
non-fatal crashes). Preventing these crashes entirely is the ideal safety outcome and would
translate into 1,547 to 2,534 lives saved and 46,896 to 65,801 MAIS 1-5 injuries prevented.
225. The above figures include benefits related to rollover crashes, a subset of all crashes.
However, in light of the relatively severe nature of crashes involving rollover, ESC's
contribution toward mitigating the problem associated with this subset of crashes should be
noted. It is anticipated that the regulation would prevent 35,680 to 39,387 rollover crashes
(1,076 to 1,347 fatal crashes and 34,604 to 38,040 non-fatal crashes). This would translate
into 1,171 to 1,465 lives saved and 33,001 to 36,420 MAIS 1-5 injuries prevented in
226. In addition, preventing crashes would also result in benefits in terms of travel delay savings
and property damage savings. It is estimated that the regulation would save $376 to $535
million, undiscounted , in these two categories ($240 to $269 million of this savings is
attributable to prevented rollover crashes).
227. In addition, the ESC gtr will also have the effect of causing all light vehicles to be equipped
with anti-lock braking systems (ABS) as a foundation for ESC. It is anticipated that some
level of benefits will result from improved brake performance on vehicles not currently
equipped with ABS, but it has not been possible to quantify them. However, it should be
noted that the potential benefits of ABS did not influence the above-discussed effectiveness
estimates for ESC, because all of the non-ESC control vehicles in the study already had
ABS. The measure of unquantified benefits relates to situations where the ABS system
activates (but the ESC system does not need to) on vehicles that were not previously
equipped with ABS.
228. The cost of this gtr will need to be calculated for each individual Contracting Party. In the
case of the U.S. (for which an estimate is already available), in order to estimate the cost of
the additional components required to equip every vehicle in future model years with an
ESC system, assumptions were made about future production volume and the relationship
between equipment found in anti-lock brake systems (ABS), traction control (TC), and ESC
systems. It was assumed that in an ESC system, the equipment of ABS is a prerequisite.
Thus, if a passenger car did not have ABS, it would require the cost of an ABS system plus
the additional incremental costs of the ESC system to comply with an ESC standard. It was
assumed that traction control (TC) was not required to achieve the safety benefits found
with ESC. Future annual U.S. production of 17 million light vehicles was estimated
(consisting of nine million light trucks and eight million passenger cars).
233. In addition, this regulation is expected to add mass to vehicles and consequently to increase
their lifetime use of fuel. Most of the added mass is for ABS components and very little is
for the ESC components. Since 99% of light trucks in the U.S. are predicted to have ABS in
MY 2011, the mass increase for light trucks is less than one pound and is considered
negligible. The average mass gain for passenger cars is estimated to be 0.97 kg, resulting
in 9.8 litres more of fuel being used over the lifetime of these vehicles. The present
discounted value of the added fuel cost over the lifetime of the average passenger car is
estimated to be $2.73 at a 7% discount rate and $3.35 at a 3% discount rate.
234. These cost estimates do not include allowances for ESC system maintenance and repair.
Although all complex electronic systems will experience component failures from time to
time necessitating repair, experience to date with existing systems is that their failure rate is
not outside the norm. Also, there are no routine maintenance requirements for ESC
3.5. "Sideslip or side slip angle" means the arctangent of the ratio of the lateral velocity to the
longitudinal velocity of the centre of gravity of the vehicle.
3.6. "Understeer" means a condition in which the vehicle's yaw rate is less than the yaw rate
that would occur at the vehicle's speed as result of the Ackerman Steer Angle.
3.7. "Yaw rate" means the rate of change of the vehicle's heading angle measured in
degrees/second of rotation about a vertical axis through the vehicle's centre of gravity.
3.8. "Peak braking coefficient (PBC)": means the measure of tyre to road surface friction
based on the max deceleration of a rolling tyre.
3.9. "Common space" means an area on which more than one tell-tale, indicator, identification
symbol, or other message may be displayed but not simultaneously.
3.10. "Static Stability Factor" means one-half the track width of a vehicle divided by the height
of its center of gravity, also expressed as SSF = T/2H, where: T = track width (for vehicles
with more than one track width the average is used; for axles with dual wheels, the outer
wheels are used when calculating "T") and H = height of the center of gravity of the vehicle.
4. GENERAL REQUIREMENTS
Each vehicle equipped with an ESC system shall meet the general requirements specified in
Paragraph 4., the performance requirements of Paragraph 5., the test procedures specified
in Paragraph 6. and the test conditions specified in Paragraph 7. of this regulation.
4.1. Functional requirements. An electronic stability control system shall be one that:
Is capable of applying braking torques individually to all four wheels
and has a
control algorithm that utilizes this capability;
Is operational over the full speed range of the vehicle, during all phases of driving
including acceleration, coasting, and deceleration (including braking), except:
When the driver has disabled ESC,
When the vehicle speed is below 20 km/h,
While the initial start-up self test and plausibility checks are completed, not to
exceed 2 minutes when driven under the conditions of Paragraph 7.10.2.,
When the vehicle is being driven in reverse;
Remains capable of activation even if the antilock brake system or traction control
system is also activated.
5.4. ESC Malfunction Detection. The vehicle shall be equipped with a tell-tale that provides a
warning to the driver of the occurrence of any malfunction that affects the generation or
transmission of control or response signals in the vehicle's electronic stability control
system. The ESC malfunction tell-tale:
Shall be displayed in direct and clear view of the driver while in the driver's
designated seating position with the driver's seat belt fastened;
Shall appear perceptually upright to the driver while driving;
Shall be identified by the symbol shown for "ESC Malfunction Tell-tale" below or the
Shall be yellow or amber in colour;
When illuminated, shall be sufficiently bright to be visible to the driver under both
daylight and night time driving conditions, when the driver has adapted to the ambient
roadway light conditions;
Except as provided in Paragraph 5.4.(g), the ESC malfunction tell-tale shall illuminate
when a malfunction exists and shall remain continuously illuminated under the
conditions specified in Paragraph 5.4. for as long as the malfunction exists, whenever
the ignition locking system is in the "On" ("Run") position;
Except as provided in Paragraph 5.4.1., each ESC malfunction tell-tale shall be
activated as a check of lamp function either when the ignition locking system is turned
to the "On" ("Run") position when the engine is not running, or when the ignition
locking system is in a position between "On" ("Run") and "Start" that is designated by
the manufacturer as a check position;
Shall extinguish at the next ignition cycle after the malfunction has been corrected in
accordance with Paragraph 7.10.4.;
May also be used to indicate the malfunction of related systems/functions, including
traction control, trailer stability assist, corner brake control, and other similar functions
that use throttle and/or individual torque control to operate and share common
components with ESC.
5.4.1. The ESC malfunction tell-tale need not be activated when a starter interlock is in operation.
5.4.2. The requirement of Paragraph 5.4.(g) does not apply to tell-tales shown in a common
5.4.3. The manufacturer may use the ESC malfunction tell-tale in a flashing mode to indicate ESC
operation and/or the operation of ESC-related systems (as listed in Paragraph 5.4 (i)).
5.5.3. A control for an ESC system whose purpose is to place the ESC system in different modes,
at least one of which may no longer satisfy the performance requirements of Paragraphs 5.,
5.1., 5.2., and 5.3., shall be identified by the symbol shown below with the text "OFF"
adjacent to the control position for this mode.
Alternatively, in the case where the ESC system mode is controlled by a multi-functional
control, the driver display shall identify clearly to the driver the control position for this mode
using either the symbol in Paragraph 5.5.2. or the text "ESC OFF".
5.5.4. A control for another system that has the ancillary effect of placing the ESC system in a
mode in which it no longer satisfies the performance requirements of Paragraphs 5., 5.1.,
5.2., and 5.3. need not be identified by the "ESC Off" identifiers in Paragraph 5.5.2.
5.6. "ESC Off" Tell-tale. If the manufacturer elects to install a control to turn off or reduce the
performance of the ESC system under Paragraph 5.5., the tell-tale requirements of
Paragraphs 5.6.1. to 5.6.4. shall be met in order to alert the driver to the lessened state of
ESC system functionality. This requirement does not apply for the driver-selected mode
referred to in Paragraph 5.5.1.(b).
5.6.1. The vehicle manufacturer shall provide a tell-tale indicating that the vehicle has been put
into a mode that renders it unable to satisfy the requirements of Paragraphs 5, 5.1., 5.2.,
and 5.3., if such a mode is provided.
5.6.2. The "ESC off" tell-tale:
Shall be displayed in direct and clear view of the driver while in the driver's
designated seating position with the driver's seat belt fastened;
Shall appear perceptually upright to the driver while driving;
Shall be identified by the symbol shown for "ESC Off" in Paragraph 5.5.2. or the text
"ESC OFF"; or
Shall be identified with the English word "OFF" on or adjacent to either the control
referred to in Paragraph 5.5.2. or 5.5.3. or the illuminated malfunction tell-tale;
Shall be yellow or amber in colour;
When illuminated, shall be sufficiently bright to be visible to the driver under both
daylight and night time driving conditions, when the driver has adapted to the ambient
roadway light conditions;
Shall remain continuously illuminated for as long as the ESC is in a mode that
renders it unable to satisfy the requirements of Paragraphs 5., 5.1., 5.2., and 5.3.;
6.2.2. The road test surface has a nominal peak braking coefficient (PBC) of 0.9, unless otherwise
specified, when measured using either:
The American Society for Testing and Materials (ASTM) E1136 standard reference
test tyre, in accordance with ASTM Method E1337-90 without water delivery, at a
speed of 40 mph; or
The method specified in the Annex 6, Appendix 2 of UNECE Regulation No. 13-H.
6.2.3. The test surface has a consistent slope between level and 1%.
6.3. Vehicle Conditions
6.3.1. The ESC system is enabled for all testing.
6.3.2. Vehicle Mass. The vehicle is loaded with the fuel tank filled to at least 90% of capacity, and
total interior load of 168 kg comprised of the test driver, approximately 59 kg of test
equipment (automated steering machine, data acquisition system and the power supply for
the steering machine), and ballast as required by differences in the mass of test drivers and
test equipment. Where required, ballast shall be placed on the floor behind the passenger
front seat or if necessary in the front passenger foot well area. All ballast shall be secured
in a way that prevents it from becoming dislodged during test conduct.
6.3.3. Tyres. The tyres are inflated to the vehicle manufacturer's recommended cold tyre inflation
pressure(s) e.g. as specified on the vehicle's placard or the tyre inflation pressure label.
Tubes may be installed to prevent tyre de-beading.
6.3.4. Outriggers. Outriggers may be used for testing if deemed necessary for test drivers' safety.
In this case, the following applies:
For vehicles with a Static Stability Factor (SSF) ≤ 1.25;
Vehicles with a mass in running order under 1,588 kg shall be equipped with
"lightweight" outriggers. Lightweight outriggers shall be designed with a maximum
mass of 27 kg and a maximum roll moment of inertia of 27 kg·m .
Vehicles with a mass in running order between 1,588 kg and 2,722 kg shall be
equipped with "standard" outriggers. Standard outriggers shall be designed with a
maximum mass of 32 kg and a maximum roll moment of inertia of 35.9 kg·m .
Vehicles with a mass in running order equal to or greater than 2,722 kg shall be
equipped with "heavy" outriggers. Heavy outriggers shall be designed with a
maximum mass of 39 kg and a maximum roll moment of inertia of 40.7 kg·m .
6.3.5. Automated steering machine. A steering machine programmed to execute the required
steering pattern shall be used in Paragraphs 7.5.2., 7.5.3., 7.6. and 7.9. The steering
machine shall be capable of supplying steering torques between 40 to 60 Nm. The steering
machine shall be able to apply these torques when operating with steering wheel velocities
up to 1,200° per second.
7.6. Slowly Increasing Steer Procedure. The vehicle is subjected to two series of runs of the
Slowly Increasing Steer Test using a constant vehicle speed of 80 ± 2 km/h and a steering
pattern that increases by 13.5° per second until a lateral acceleration of approximately 0.5 g
is obtained. Three repetitions are performed for each test series. One series uses
counterclockwise steering, and the other series uses clockwise steering. The maximum
time permitted between each test run is five minutes.
7.6.1. From the Slowly Increasing Steer tests, the quantity "A" is determined. "A" is the steering
wheel angle in degrees that produces a steady state lateral acceleration (corrected using
the methods specified in Paragraph 7.11.3.) of 0.3 g for the test vehicle. Utilizing linear
regression, "A" is calculated, to the nearest 0.1°, from each of the six Slowly Increasing
Steer tests. The absolute value of the six A's calculated is averaged and rounded to the
nearest 0.1° to produce the final quantity, A, used below.
7.7. After the quantity "A" has been determined, without replacing the tyres, the tyre conditioning
procedure described in Paragraph 7.5. is performed immediately prior to conducting the
Sine with Dwell Test of Paragraph 7.9. Initiation of the first Sine with Dwell test series shall
begin within two hours after completion of the Slowly Increasing Steer tests of
7.8. Check that the ESC system is enabled by ensuring that the ESC malfunction and "ESC Off"
(if provided) tell-tales are not illuminated.
7.9. Sine with Dwell Test of Oversteer Intervention and Responsiveness. The vehicle is
subjected to two series of test runs using a steering pattern of a sine wave at 0.7 Hz
frequency with a 500 ms delay beginning at the second peak amplitude as shown in
Figure 2 (the Sine with Dwell tests). One series uses counterclockwise steering for the first
half cycle, and the other series uses clockwise steering for the first half cycle. The vehicle is
allowed to cool-down between each test run of 90 seconds to five minutes, with the vehicle
7.9.1. The steering motion is initiated with the vehicle coasting in high gear at 80 ± 2 km/h.
7.9.2. The steering amplitude for the initial run of each series is 1.5A, where "A" is the steering
wheel angle determined in Paragraph 7.6.1.
7.9.3. In each series of test runs, the steering amplitude is increased from run to run, by 0.5A,
provided that no such run will result in a steering amplitude greater than that of the final run
specified in Paragraph 7.9.4.
7.9.4. The steering amplitude of the final run in each series is the greater of 6.5A or 270°, provided
the calculated magnitude of 6.5A is less than or equal to 300°. If any 0.5A increment, up to
6.5A, is greater than 300°, the steering amplitude of the final run shall be 300°.
7.9.5. Upon completion of the two series of test runs, post processing of yaw rate and lateral
acceleration data is done as specified in Paragraph 7.11.
7.11.5. Lateral acceleration, yaw rate and steering wheel angle data channels are zeroed utilizing a
defined "zeroing range". The methods used to establish the zeroing range are defined in
Paragraphs 126.96.36.199. and 188.8.131.52.
184.108.40.206. Using the steering wheel rate data calculated using the methods described in
Paragraph 7.11.4., the first instant steering wheel rate exceeding 75 deg/sec is identified.
From this point, steering wheel rate shall remain greater than 75 deg/sec for at least
200 ms. If the second condition is not met, the next instant steering wheel rate exceeding
75 deg/sec is identified and the 200 ms validity check applied. This iterative process
continues until both conditions are ultimately satisfied.
220.127.116.11. The "zeroing range" is defined as the 1.0 second time period prior to the instant the steering
wheel rate exceeds 75 deg/sec (i.e. the instant the steering wheel velocity exceeds
75 deg/sec defines the end of the "zeroing range").
7.11.6. The Beginning of Steer (BOS) is defined as the first instance filtered and zeroed steering
wheel angle data reaches -5° (when the initial steering input is counterclockwise) or +5°
(when the initial steering input is clockwise) after time defining the end of the "zeroing
range". The value for time at the BOS is interpolated.
7.11.7. The Completion of Steer (COS) is defined as the time the steering wheel angle returns to
zero at the completion of the Sine with Dwell steering manoeuvre. The value for time at the
zero degree steering wheel angle is interpolated.
7.11.8. The second peak yaw rate is defined as the first local yaw rate peak produced by the
reversal of the steering wheel. The yaw rates at 1.000 and 1.750 seconds after COS are
determined by interpolation.
7.11.9. Determine lateral velocity by integrating corrected, filtered and zeroed lateral acceleration
data. Zero lateral velocity at BOS event. Determine lateral displacement by integrating
zeroed lateral velocity. Zero lateral displacement at BOS event. Lateral displacement at
1.07 seconds from BOS event is determined by interpolation.