TRB Special Report 308: The Safety Challenge and Promise of Automotive Electronics Insights from Unintended Acceleration (2012) / Chapter Skim
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Pages 133-168
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From page 133... ...
5 Review of National Highway Traffic Safety Administration Initiatives on Unintended Acceleration The statement of task for this study requests "an independent review of past and ongoing industry and NHTSA [National Highway Traffic Safety Administration] analyses to identify possible causes of unintended acceleration." As noted in Chapter 1, NHTSA's Office of Defects Investigation (ODI)
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134 || The Safety Promise and Challenge of Automotive Electronics investigations conducted and supported by ODI on the basis of its definition of unintended acceleration and its purposes in conducting the investigations. ODI informed the committee that it investigates consumer complaints to determine whether the conditions and behaviors reported result from a vehicle-related deficiency that presents a public safety risk.2 The agency's investigations inform decisions about whether specific follow-up steps are warranted, such as influencing or ordering a manufacturer safety recall, amending a Federal Motor Vehicle Safety Standard (FMVSS)
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Review of NHTSA Initiatives on Unintended Acceleration || 135 and comment on the continued relevance of the criteria derived from that report, which is often referred to as the Silver Book. More recently, questions have arisen about whether vulnerabilities in electronic throttle control systems (ETCs)
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136 || The Safety Promise and Challenge of Automotive Electronics Past NHtsa INItIatIves oN UNINteNded acceleratIoN As indicated in Chapter 1, two major investigations of unintended acceleration were commissioned by NHTSA during the 1980s. The first (Walter et al.
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Review of NHTSA Initiatives on Unintended Acceleration || 137 deficiency was found. The latter cases tended to involve vehicles that were accelerating abruptly from a stopped or parked position or from a low travel speed, often accompanied by a reported loss of braking.
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138 || The Safety Promise and Challenge of Automotive Electronics of engine load. The system, composed of an electronic control unit and an electromechanical air valve, was prone to defects that caused a high idle speed and periodic engine surging.7 The TSC team noted that because of their intermittent nature, these behaviors may not have been detected during premarket testing of the Audi or in postcrash investigations by ODI and others.
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Review of NHTSA Initiatives on Unintended Acceleration || 139 for a sticking throttle caused by problems such as frayed or kinked cables, broken springs, and stuck pedals. They concluded that such mechanical faults were not likely to be causes of unexplained cases of unintended acceleration since their origins would be evident during postevent inspection of the vehicle.
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140 || The Safety Promise and Challenge of Automotive Electronics assumed to be delayed somewhat to simulate a driver's emergency response to the onset of acceleration, will quickly stop a vehicle accelerating from a stationary position or low travel speed.10 Unintended acceleration accompanied by unexplained brake loss had long been associated with pedal misapplication.11,12 The TSC investigators knew this and questioned whether certain vehicle-related factors could be responsible for drivers applying the wrong pedal after being startled by a vehicle-related condition or behavior. They surmised that phenomena such as engine surging, high idling, or even unexpected noises could induce this effect, especially among drivers unfamiliar with the vehicle, its operating characteristics, and its control layout.
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Review of NHTSA Initiatives on Unintended Acceleration || 141 ical problems (e.g., stuck pedals and accelerator cables) and pedal obstructions (such as floor mat entrapment)
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142 || The Safety Promise and Challenge of Automotive Electronics 15 recalls affecting 13 manufacturers (OIG 2011, 5) .15 Eight of the investigations involved Toyota vehicles and led to two manufacturer recalls.
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TABLE 5-1 Summary of ODI Investigations and Inquiries on Unintended Acceleration Involving Toyota Vehicles, 2003–2010 Vehicles Involved (Toyota and Lexus Makes) ODI Investigation or Inquiry Findings and Conclusions Action Lexus GS and Response to a consumer petition: A petitioner to ODI After normalization to account for Assessment closed LS (Model Years reported experiencing multiple events of unintended vehicle production data, ODI did not 1997–2000)
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TABLE 5-1 (continued) Summary of ODI Investigations and Inquiries on Unintended Acceleration Involving Toyota Vehicles, 2003–2010 Vehicles Involved (Toyota and Lexus Makes)
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Sienna (Model ODI review of complaint data: ODI's Early Warning Vehicle inspections by ODI and Toyota Toyota issued a Year 2004) Division recommended a review of the Model Year found that the trim panel on the center recall to fix the Investigation 2004 Sienna because the Early Warning Reporting data console could obstruct the accelerator panel compoopened 2008 showed an unexplained trend of pedal interference in pedal.
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TABLE 5-1 (continued) Summary of ODI Investigations and Inquiries on Unintended Acceleration Involving Toyota Vehicles, 2003–2010 Vehicles Involved (Toyota and Lexus Makes)
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Review of NHTSA Initiatives on Unintended Acceleration || 147 who had experienced unintended acceleration and subsequently reviewed the consumer complaint data [Vehicle Owner's Questionnaire (VOQ)
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148 || The Safety Promise and Challenge of Automotive Electronics During the floor mat investigations, ODI mailed a survey to more than 1,800 owners of the 2007 Lexus ES 350 requesting information on occurrences of unintended acceleration. Of the approximately 600 owners who responded, 10 percent stated that they had experienced unintended acceleration, and 6 percent complained of occasional pedal interference from floor mats.
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Review of NHTSA Initiatives on Unintended Acceleration || 149 The involvement of the Lexus ES 350, which had been among the Toyota models subject to the earlier floor mat recall, in the Santee crash prompted ODI to question whether Toyota's recall plan was adequate and whether other precautions were needed to prevent a recurrence of such outcomes.21 Toyota responded by issuing a second recall to reshape the accelerator pedal to reduce the potential for floor mat entrapment. For recalled vehicles equipped with the start–stop button, Toyota also installed software that would cause application of the brake to override the throttle in the event of entrapment.22 Pedal Sticking Recall In late 2009, after the issuance of Toyota's second recall associated with floor mats, ODI observed that some owners of Toyota vehicles were complaining about the need to press harder than normal on the accelerator pedal to increase vehicle speed, and some were also finding that the pedal was slow to return to a rest position after it was released.
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150 || The Safety Promise and Challenge of Automotive Electronics FIGURE 5-1 Consumer complaints of unintended acceleration (UA) in relation to publicized events, as reported by NHTSA.
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Review of NHTSA Initiatives on Unintended Acceleration || 151 publicized events as well as NHTSA's announcement of its intention to commission studies by NASA and the National Research Council [referred to as the National Academy of Sciences (NAS) in the figure]
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152 || The Safety Promise and Challenge of Automotive Electronics TABLE 5-2 Unintended Acceleration Consumer Complaints Received by NHTSA, 2000–2010 Item Number Total consumer complaints (January 1, 2000, to March 5, 2010) 426,911 Complaints identified by key words associated with unintended acceleration 19,269 Complaints after manual review of narratives (Model Year 1998–2010 9,701 vehicles only)
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Review of NHTSA Initiatives on Unintended Acceleration || 153 ODI concluded that the low initiation speed incidents are highly suggestive of pedal misapplication for the reasons explained in the earlier discussion of the Silver Book. ODI further concluded that many of the incidents involving vehicles in which the onset of acceleration occurred at medium and higher speeds (31 percent of complaints)
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154 || The Safety Promise and Challenge of Automotive Electronics claimed to have applied the brakes. The analysis also indicated a number of cases in which the acceleration began at highway speeds; they occurred among the Model Year 2007 to 2010 vehicles that had been subject to the floor mat recalls.
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Review of NHTSA Initiatives on Unintended Acceleration || 155 showed that the brake had been applied late in the crash, indicated by the brake light switch transitioning to "on" either 1 second before or at the time of the crash. The significantly delayed brake pedal application (suggesting a late driver correction after application of the wrong pedal)
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156 || The Safety Promise and Challenge of Automotive Electronics acceleration and brake performance testing to quantify braking effectiveness with and without power assistance. Tests included baseline acceleration and then a series of acceleration tests while applying pressure to the brake pedal by using the forces required for testing to comply with NHTSA's brake performance regulation (FMVSS 135)
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Review of NHTSA Initiatives on Unintended Acceleration || 157 Pedal Layout and Driver Interface The orientation, location, and operation of the accelerator and brake pedals in the Camrys were tested and measured. NHTSA reported that these measurements did not provide any basis for concluding that pedal misapplication was more likely in the Camry than in other vehicles (NHTSA 2011, 54)
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158 || The Safety Promise and Challenge of Automotive Electronics causing unintended acceleration in the fleet, the NESC team reviewed consumer complaints for hallmarks of the failures and tested vehicles and components previously used by drivers alleging unintended acceleration. On the basis of its vulnerability analysis, the NESC team identified the following two scenarios that it described as having at least a theoretical potential to produce unintended acceleration characteristic of a large throttle opening: (a)
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TABLE 5-5 Abbreviated FMEA of Toyota ETC by NASA Conditions Failure Condition Physical or Necessary for and Symptoms Electronic Range of Failure System Failure Electronics Failure to Occur, Found in Real Evidence, Failure Throttle Effect Response: Fail-Safe System-Level Component Failure Mode World Detection Opening Braking? Modes Applied Prevention Functional Area: Pedal Command Pedal Position sensor Pedal sensor DTC for high, low, Throttle does Limp-home mode -- Idle mode fuel sensors fail high, low, failures in war- outside operational not open with throttle limited to <15°.
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From page 160... ...
TABLE 5-5 (continued) Abbreviated FMEA of Toyota ETC by NASA Conditions Failure Condition Physical or Necessary for and Symptoms Electronic Range of Failure System Failure Electronics Failure to Occur, Found in Real Evidence, Failure Throttle Effect Response: Fail-Safe System-Level Component Failure Mode World Detection Opening Braking?
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Review of NHTSA Initiatives on Unintended Acceleration || 161 acceleration indicative of a large throttle opening, but some produced engine slowing and stalling. After contacting a consumer who had complained about unusual accelerator pedal responses, ODI recovered the vehicle's accelerator pedal assembly, which it turned over to the NESC team for analysis.
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162 || The Safety Promise and Challenge of Automotive Electronics component, the engine control module, the throttle actuator, the accelerator pedal, any related wiring or harness connectors, and any DTCs that could be associated with a failure of the ETC. In reviewing the warranty data generally, ODI had determined that claim rates for the Camry components (per vehicle sold)
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Review of NHTSA Initiatives on Unintended Acceleration || 163 and not one "occurring in the real world" (NHTSA 2011, 63)
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164 || The Safety Promise and Challenge of Automotive Electronics the driver releases the accelerator pedal. Degraded or failed braking is often asserted along with both of these forms of unintended acceleration.
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Review of NHTSA Initiatives on Unintended Acceleration || 165 Finding 5.4: Not all complaints of unintended acceleration have the signature characteristics of pedal misapplication; in particular, when severe brake damage is confirmed or the loss of braking effectiveness occurs more gradually after a prolonged effort by the driver to control the vehicle's speed, pedal misapplication is improbable, and NHTSA reported that it treats these cases differently. In its investigations of such cases, NHTSA has usually concluded that the acceleration was caused by faulty mechanical components or the accelerator pedal becoming stuck or entrapped, often by a floor mat.
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From page 166... ...
166 || The Safety Promise and Challenge of Automotive Electronics or any other vehicle defects as possible causes. Unintended acceleration resulting from pedal entrapment or pedal misapplication would not be expected to be revealed by warranty repair data; thus, in this sense the absence of suspect patterns in the warranty data corroborated ODI's conclusions that floor mat entrapment was the cause of the increase in the Toyota complaints uncharacteristic of pedal misapplication.
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Review of NHTSA Initiatives on Unintended Acceleration || 167 Reinhart, W
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