Cars Gone Wild: The Major Contributor to Unintended Acceleration in Automobiles is Pedal Error

Cars Gone Wild: The Major Contributor to Unintended Acceleration in Automobiles is Pedal Error

Front Psychol.

2010 ; 1 : 209 . department of the interior :10.3389/fpsyg.2010.00209



PMID : 21833265

Cars Gone Wild: The Major Contributor to Unintended Acceleration in Automobiles is Pedal Error

1,2, * and 3,4

Richard A. Schmidt

1Department of Psychology, University of California, Los Angeles, Los Angeles, CA, USA 2Human Performance Research, Marina del Rey, CA, USA Find articles by Richard A. Schmidt

Douglas E. Young

3Exponent Inc., Failure Analysis Associates, Los Angeles, CA, USA 4Department of Kinesiology, California State University, Long Beach, CA, USA Find articles by Douglas E. Young Author information Article notes Copyright and License information Disclaimer 1Department of Psychology, University of California, Los Angeles, Los Angeles, CA, USA 2Human Performance Research, Marina del Rey, CA, USA 3Exponent Inc., Failure Analysis Associates, Los Angeles, CA, USA 4Department of Kinesiology, California State University, Long Beach, CA, USA Edited by : Gabriele Wulf, University of Nevada, Las Vegas, USA Reviewed by : Gabriele Wulf, University of Nevada, Las Vegas, USA ; Rebecca Lewthwaite, Rancho Los Amigos National Rehabilitation Center and the University of Southern California, USA *Correspondence : Richard A. Schmidt, Human Performance Research, 135 Lighthouse Mall, Marina del Rey, CA 90292-5992, USA. e-mail : moc.hcraeser-ph @ tdimhcsar This article was submitted to Frontiers in Movement Science and Sport Psychology, a peculiarity of Frontiers in Psychology .Copyright © 2010 Schmidt and Young. This is an open-access article subject to an single license agreement between the authors and the Frontiers Research Foundation, which permits unrestricted function, distribution, and reproduction in any medium, provided the original authors and generator are credited .


“ Unintended-acceleration ” automobile accidents typically begin when the driver first enters the cable car, starts the engine, and intends to press his/her right foot on the brake while shifting from Park to a drive gear ( Drive or Reverse ). The driver reports an unintended ( uncommanded ) full-throttle acceleration, coupled with a loss of braking, until the sequence ends in a crash. Pedal misapplications – where the correctly foot contacts the accelerator rather of the brake that was intended – have been linked to these accidents ( Schmidt, 1989, 1993 ) which, in the 1980s, were thought to occur entirely at the depart of a drive cycle ( and/or with the cable car in Park ). But, in 1997, we identified over 200 pedal point errors as the lawsuit of accidents reported in the North Carolina database ; these crashes occurred during the drive bicycle ( Schmidt et al., 1997 ), and/or with the vehicle in a gearing other than Park. Our deliver solve provides a more exhaustive analysis of these North Carolina Police Accident Reports from 1979 to 1995. The huge majority of pedal misapplications ( over 92 % ) ( a ) occurred during the drive cycle, ( barn ) were by and large in “ unhurried ” conditions, and ( c ) were flatly classify from those events referred to as unintended-acceleration episodes at start-up. These ideas are explanatory for the holocene ( 2009–2010 ) billow of unintended-acceleration reports, possibly even suggesting that all of these crashes are caused by bicycle errors, and that none of them are based on some vehicle defect ( south ). Keywords:

automobile accidents, unintended-acceleration, pedal misapplications, vehicle defect


The condition “ unintended acceleration ” ( UA – sometimes called “ sudden acceleration ” ) was coined in the 1980s to describe a type of car accident that was attracting considerable attention at the clock. In these episodes, the driver would report that, as he/she was initiating a drive hertz, after starting the engine, placing the veracious foot lightly on the brake ( to prevent the car from “ creeping ” ), and shifting from Park to a drive gear ( normally Park or Reverse, depending on the situation ), the fomite would go to an uncommanded ( i.e., unintended ) wide-open-throttle condition, coupled with an apparent personnel casualty of braking effectiveness ( Pollard and Sussman, 1989 ; Reinhart, 1989 ; Schmidt, 1989, 1993 ). The episode would often end with a barge in. In the 1980s, there was a rush of UA reports, representing about every mark of automobile. This situation resulted in a delirious search by three federal government agencies, respective car makers, and respective secret inquiry firms, for some electrical/mechanical defect that would cause these events. none was ever found. This naturally resulted in considerable publicity ( e.g., newspaper and magazine articles, and even a “ 60 Minutes ” television report ; CBS, 1986 ) and substantial populace awareness.

Over the adjacent few decades, this site gradually faded from public awareness. recently, however, in 2009–2010, a similar position has apparently returned. For many of us who worked on this problem in the 1980s, the current situation brings the problem again to mind again, creating the suspicion that the same phenomenon are still operating ( or are operating again ). In the 1980s, a number of researchers began to suspect that these episodes might have a human-error component ( for example, Schmidt, 1989 ; Reinhart, 1994 ), and that a search for an electro-mechanical defect might be misguided. The essential theme was that the driver, intending to put the right foot on the brake, would occasionally place the foot on the catalyst by error. then, when the cable car moved when a drive gear was engaged, the driver would press hard on the “ brake ” to stop it, the vehicle would go even faster, resulting in more “ brake ” application, usw., until the vehicle soon was in a wide-open-throttle condition ; the driver ( who was constantly panicked ) was rendered incapable of diagnosing the position in the few seconds before a crash occurred. In the 1980s, these accidents were chiefly associated with the begin of a drive cycle ( and/or otherwise initiating driving with the vehicle in Park gearing, such as at a fast-food drive-through or at an outdoor bank-teller ‘s station ). These types of accidents led to National Highway Traffic Safety Administration ‘s ( NHTSA ) formal definition which tended to confine UA crashes to strictly start-up events ( Pollard and Sussman, 1989 ). Less well known are the frequency and type of bicycle errors that occur during the drive cycle ( i.e., with the fomite already in Drive or Reverse ). These events do not fall easily under the above NHTSA definition, even though ( subsequent to the error ) they seem to have many features in coarse with UA ( full accelerator, relatively retentive duration : respective seconds or longer ). In 1997, we ( Schmidt et al., 1997 ) found a surprise number and variety of pedal errors leading to accidents, but which were not the “ official, ” NHTSA-defined UA situation ( because they did not start with the vehicle in Park or at abject initial speed ). In our initial employment ( Schmidt et al., 1997 ), we examined the North Carolina Police Accident Report database for the years 1979 and 1980 to determine the kinds of pedal errors that were made, the conducive factors, and the frequency of these events. We discovered 219 accidents for which the driver admitted having made a bicycle error as a aim cause of the crash. These pedal point errors occurred in many different driving situations ( i.e., all with the vehicle being in one of the drive gears other than Park when the episode began ). We were surprised that these accidents appeared to represent a basically different character of accident trigger from that previously classified ( by NHTSA ; Pollard and Sussman, 1989 ) as UA. One principal deviation is that the drivers in our pedal-error probe know ( and admitted ) that they had made an error, and offered this information to the investigate authorities. however, the drivers in NHTSA-defined UA episodes typically did not know that they had made a pedal error ; in fact, the latter drivers were typically emphatic that they did not make a bicycle mistake. This distinction means that, if a pedal erroneousness caused an NHTSA-defined UA episode, the driver would report the causal agent in terms such as accelerator malfunction, stick choke, failed brakes, etc. however, for the second class of pedal-error accident ( caused by an accept pedal mistake, at accelerate, and with the fomite not being in Park ), a different character of accident description would be given by the driver ; here language such as hit ( i, the wrong pedal point ), miss ( the brake ), slipped ( from brake to accelerator ), usw. In the present wallpaper, we expanded our research for this moment type of pedal-misapplication crash, using North Carolina data from the years 1979 through 1995. here, we report our examen of these two classes of accidents, and their relative frequencies, asking whether they can be considered as separate phenomena or as variants of the same phenomenon .

Materials and Methods

The accident-report database from North Carolina contains over one million accidents of about all types, where the accident was sufficiently unplayful to warrant a patrol report. The database includes the direct, written statement of the investigating officer describing how the accident happened, based in separate on statements made by the driver ( s ) of the byzantine fomite ( s ) and/or eye-witnesses or passengers. These narratives can be searched for assorted samara words, depending on the overall research finish. Our keyword evaluation of these narrative statements produced two different searches : one for recognized and/or admitted pedal errors, and a irregular for NHTSA-defined UA episodes where the driver stated that his/her correct foot was on the brake, and was not on the catalyst ( i.e., pedal mistake was not admitted ). A cardinal question was whether or not these two searches would result in overlapping subsets of the accident database. We first searched for keywords such as bracken, metrical foot, gasoline, pedal, and air combat command ( for accelerate, accelerator, etc. ), resulting in more than 94,000 accident reports. next, we searched this subset with more detailed keywords to isolate accidents thought to be caused by pedal misapplications, such as miss, skid, alternatively, etc. This trimmed the fixed to about 20,000 accidents for which we were at least fishy that a pedal error had led to the crash. The adjacent step was to read the remaining narratives to verify that the accident was, in fact, related to a pedal error. This process eliminated many cases which were not associated with pedal misapplications ( for example, “ The driver swerved to miss a pawl ” ). The final resultant role was a set of 3740 accidents that satisfied our pedal-error criteria. such a subset will surely underestimate the total count of such accidents, as many drivers are reluctant to admit their error ; and, some crashes are identical minor and do not result in accident reports. And, of run, an strange issue of bicycle errors may have been corrected before a crash actually occurred. In regulate to find NHTSA-defined UA events, we reviewed the pedal-error accidents identified in this late study to determine if any of these cases could besides be construed as an NHTSA-defined “ unintended-acceleration ” event, where a driver ( a ) lurch from Park to either Drive or Reverse at the originate of a repel cycle, ( b-complex vitamin ) incurs a sudden and unexpected vehicle acceleration, ( hundred ) reports a perceive failure of the brakes, and ( d ) reports a malfunction of the strangle or accelerator pedal. This analysis, however, produced no crashes that fit the NHTSA criteria for UA. We then searched the accident database ( for the years from 1979 to 1995 ) using key words believed to characterize NHTSA-defined UA episodes based on the accident narratives. These words included sudden, malfunction, runaway, stuck, transformation, accelerator, gear, control ( for out of control ), and produced over 43,000 accident records. We then reduced the set by combining assorted keystone words ( for example, catalyst stick ), and adding other keywords, which included terms such as park, leap, beginning, unexpect ( for unexpected or unexpectedly ), etc., to eliminate those accidents that were clearly not pedal-error based ( for example, accidents involving a car door stuck open ). We then read and categorized these narratives .


Of the accidents identified, two distinct sets of pedal errors were found : ( a ) 3740 accidents which were intelligibly caused by pedal misapplication, and ( b ) a non-overlapping 39 reports that were NHTSA-defined UA episodes. This represents an authoritative find oneself, in that our earlier understanding of bicycle errors was that they were associated chiefly with the originate of the force bicycle. With this evidence, it is now clear that pedal misapplications can occur frequently in respective extra ways, possibly as Rogers and Wierwille ( 1988 ) have found in simulators .


The first of several classifications concerned whether the driver was parking or driving. “ Parking ” involved those situations where the car was in a parking batch, home garage, or was being parked in a parking space on the street. “ Driving ” included all other situations, where it was clear that the vehicle was being driven on the road or highway ( and consequently was not in Park ). Some of the crashes that occurred while driving might well have been classed as park accidents, however – for example, where the vehicle was being driven to a parking space. future, for each of these accidents we coded the bicycle embezzlement as either a skid from the brake, or as hitting the “ faulty bicycle ” ( the catalyst ) without inaugural slipping from the brake. besides, we classified the scenario as ( 1 ) hurried, ( 2 ) unhurried, or ( 3 ) distracted to identify the urgency or other extenuating circumstances involved in the attempted brake lotion. For the drive accidents, we made one extra categorization concerning the circumstances of the pedal point application. These were classified as accidents in which the vehicle or driver was ( 1 ) turn, ( 2 ) slow ( “ normally ” ), ( 3 ) stopped, or ( 4 ) early. For the park accidents, we classified them as occurring in the forward or backward commission .

Parking accidents

merely 279 of the 3740 accidents were involved in what we considered parking operations ( see Table ). These were divided between moving forth ( 216 ) and back ( 63 ). In terms of mechanism of the misapplication, 126 accidents were caused by slips from the brake, and 153 occurred because the driver hit the “ ill-timed pedal ” for some rationality. entirely 19 of the accidents were classified as hurried, with 213 not hurried, and 47 distracted. It is curious that the about half of the accidents occurring in parking operations happened because the driver for some reason hit the “ wrong pedal, ” with over three-quarters of the accidents being under non-hurried conditions .

Table 1

CharacteristicNumberSlip126“Wrong pedal”153Forward direction216Backward direction63Hurried19Unhurried213Distracted47Open in a separate window

Driving accidents

The overpower majority of accidents caused by pedal misapplications occurred under driving conditions ( 92.5 %, see table ). Of these, 2640 were caused by a slip, whereas the remainder ( 821 ) resulted from the driver pressing the “ wrong pedal. ” besides, there were more unhurried drive accidents ( 2938 ) as compared to those hurried ( 268 ) or distracted ( 255 ). This vogue is similar to that seen in the parking actions .

Table 2

CharacteristicNumberSlip2640“Wrong pedal”821Hurried268Unhurried2938Distraction255Slowing (“normally”)793Turning231Stopped673Other1641Open in a separate window The circumstances surrounding the pedal misapplications were then separated into three categories ( see Table ). The largest single category was slowing ( “ normally ” ), with 793 accidents, followed by stop and turn, with 673 and 231 accidents, respectively. We could not classify 1641 accidents from the narratives alone. We found an apparent interaction between the type of pedal embezzlement and the drive circumstances surrounding it ( see Table ). First, for accidents that occurred while the fomite was stopped, most ( 604 ) were associated with slip of the metrical foot from the bracken, whereas only 69 were caused by hitting the “ wrong pedal. ” On the early hand, for accidents wherein the driver was making a bend, most ( 134 ) were associated with the driver hitting the “ incorrect pedal point, ” whereas only 97 of these turning accidents involved slips from the brake .

Table 3

ActionType of pedal errorSlip“Wrong pedal”Stopped60469Slowing613180Turning97134Open in a separate window

Unintended-acceleration episodes

Keyword-search results for NHTSA-defined UA episodes produced merely 39 accidents ( Table ). In these accidents, the drivers ’ accident description to the reporting officer indicated that the vehicle abruptly accelerated immediately or soon after the vehicle was placed into Drive or Reverse from either Park or Neutral. In these accidents, there was a fairly uniform description of the accident by the drivers. about all of the accidents occurred in a parking fortune, driveway, or parking space ; one incident took stead at an outdoor service window of a bank. seventy-two percentage ( 28/39 ) of the accidents involved a forward acceleration of the vehicle. And, in the majority of these accidents ( 62 %, 24/39 ), the driver indicated that the catalyst ( or throttle ) malfunctioned ( for example, hang, stick ) ; none of the drivers attributed their accidents to human erroneousness .

Table 4

Driving circumstancesNumberParking38Other1Forward direction28Backward direction11Accelerator problem24Problem unknown15Human error0Open in a separate window


consistent with our earlier findings ( Schmidt et al., 1997 ), these data distinctly contradict earlier ideas that pedal misapplications are associated only with the start of a drive cycle, such as in the NHTSA-defined UA episodes ( for example, Pollard and Sussman, 1989 ; Schmidt, 1989 ). We find that the consuming majority of the pedal misapplications ( about 99 % ) occurred after initial start-up, and a amazingly modest share ( only about 1 % ) were NHTSA-defined UA episodes. The findings besides provide interesting penetration about how such bare limb movements in automobiles lead to on-road accidents of diverse types. Contrary to the notion that pedal point errors occurred chiefly as a solution of being hurried ( or distracted ) – both of which could lead to a debauched reaction, and, therefore, a less-accurate response ( Schmidt et al., 1979 ) – a majority of the pedal misapplications occurred under unhurried conditions. besides, the type of erroneousness where the driver hit the “ wrong pedal ” occurs more frequently in driving situations that involve turning, possibly indicating that there is an influence of the amphetamine limb or body that creates a more erroneous lower-limb condition. clearly, these findings on pedal misapplications point out the need to understand more completely the processes that produce pedal-based accidents on the road. several aspects of our data deserve foster study. Two main classes of explanations have been proposed for pedal errors : errors in reception choice ( for example, turn right rather than left ), and errors in reply execution ( for example, moving slightly excessively army for the liberation of rwanda ). Schmidt ( 1989 ) has argued that UAs behave like response-execution errors in many ways, sensitive to the same factors that influence variability in human aiming movements, and are unlikely to be recognized as errors by drivers who have equitable made them. many of the pedal point errors that occur during drive, however, and which are reported as such by drivers, may be of this type ( for example, Rabbitt and Rodgers, 1977 ; Reason, 1990 ) ; such errors are susceptible to being recognized by performance-monitoring mechanisms. Our data here can help us understand some fundamental principles of pedal misapplications. The NHTSA-defined UA events appear to be caused chiefly by an error in aiming the foot toward the brake during a closely coincident shift from Park to one of the drive gears, Drive or Reverse ( Schmidt, 1989 ). This type of mistake was recognized in the 1980s, and interlocks were designed to prevent them. This mesh prevented this type of UA by locking the transfer lever in Park until the brake pedal was depressed. If a pedal embezzlement should be made at the begin of a drive cycle ( i.e., pressing the accelerator quite than the brake that was intended ), the vehicle will not move, as it is safely locked in Park. These interlocks were overwhelmingly successful in reducing NHTSA-defined UAs ( Reinhart, 1994 ), decreasing their incidence by approximately 60 %. besides this success of the switch interlocks served as a crucial test of the hypotheses that UA was caused by ( a ) pedal misapplications vs. ( boron ) some electro-mechanical vehicle defect. indeed, if NHTSA-defined UA is caused by a fomite defect, then locking the transmission in park until one of the driver ‘s feet is on the brake, preventing a UA event, supports a pedal-misapplication theory, and rejects a theory involving some fomite blemish.

To this understand, we immediately add the determine that these pedal misapplications can occur in other ways than at vehicle start-up. They can occur during a drive cycle when the vehicle has already been shifted from Park to Drive or Reverse, under which conditions the shift interlocks can no farseeing be effective ( because the vehicle is no longer in Park ). And, this latter character of UA ( after fomite start-up ) appears to be far more frequent than the episodes occurring at start-up ; our data show that only about 1 % of the UA episodes are of the type defined by NHTSA at start-up, the remainder being caused by bicycle misapplications after start-up. We think that his last observation helps us understand why all of the UA episodes were not eliminated by the car-makers ’ borrowing of some form of the stir interlocks in the 1980s ; some of the pedal point misapplications credibly occurred after the car had been shifted from Park. last, in the site involving UA in the 1980s, despite formal searches by a number of research groups, no electro-mechanical defect was always found that would account for the accidents. And, since we have considerable tell that UAs can be caused by pedal misapplications, we are left with the possibility that all of the 1980s UAs were pedal-error based. With the contemporary scend in reported UA events, the situation is about the like. Granted, some have suggested that the UAs can be caused by sticking pedals or by floor mats trapping the catalyst pedal point ; but these explanations can account for merely a small act of these events. This raises the possibility that, as with UA in the 1980s, the majority, or even basically all of the contemporary UAs may be based on bicycle misapplications, with none being caused by some fomite defect ( mho ) ( Schmidt, 2010 ) .

Conflict of Interest Statement

The authors declare that the research was conducted in the absence of any commercial or fiscal relationships that could be construed as a potential conflict of matter to .

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Category : Car Brakes