Tuesday, February 17, 2015

From Dr. Anderson - Sudden Unintended Acceleration

Links below to Dr. Anderson's thorough explanation of the FAILURES that jeopardize so many lives!


Independent Electrical Engineering Consultant, Newcastle-upon-Tyne NE3 4XY, U.K. (e-mail: antony.anderson@onyxnet.co.uk).


For three decades, sudden acceleration (SA) incidents have been reported, where automobiles

accelerate without warning. These incidents are often diagnosed as no fault found. Investigators, who follow the line of diagnostic reasoning from the 1989 National Highway Traf c Safety Administration (NHTSA) SA report, tend to conclude that SAs are caused by driver pedal error. This paper reviews the diagnostic process in the NHTSA report and nds that: 1) it assumes that an intermittent electronic malfunction should be reproducible either through in-vehicle or laboratory bench tests without saying why and 2) the consequence of this assumption, for which there appears to be no forensic precedent, is to recategorize possible intermittent electronic failures as proven to be nonelectronic. Showing that the supposedly inescapable conclusions of the NHTSA report concerning electronic malfunctions are without foundation opens the way for this paper to discuss electronic intermittency as a potential factor in SA incidents. It then reports a simple practical experiment that shows how mechanically induced electrical contact intermittencies can generate false speed signals that an automobile speed control system may accept as true and that do not trigger any diagnostic fault codes. Since the generation of accurate speed signals is essential for the proper functioning of a number of other automobile safety-critical control systems, the apparent ease with which false speed signals can be
generated by vibration of a poor electrical contact is obviously a matter of general concern. Various ways of reducing the likelihood of SAs are discussed, including electrical contact improvements to reduce the likelihood of generating false speed signals, improved battery maintenance, and the incorporation of an independent fail-safe that reduces engine power in an emergency, such as a kill switch.


Contact intermittency, speed sensor, electronic speed control, cruise control, sudden

acceleration, electronic throttle control, functional safety.





Since the early 1980s numerous instances have been reported

of automobiles allegedly suddenly accelerating. Sudden

acceleration (SA) incidents fall into three main categories:

1) SA incidents from at or near standstill (Forward/



2) SA incidents when vehicle is or has been moving -

speed control

not on;

3) SA incidents when vehicle is moving - speed control



These three categories are further broken down in

Appendix I. The majority of incidents fall into the rst


A number of examples are detailed in Appendix II.

category and seem to occur when the vehicle is at or near

standstill and Appendix II provides some examples.

Sudden acceleration (SA) incidents

2 appear to happen

unexpectedly and in many cases drivers claim that they have

been unable to regain control by braking. Serious injuries and

death have sometimes resulted. There have been a number of

cases where as a result of a SA incident, drivers have been

prosecuted for vehicular homicide and have been sentenced

lengthy prison sentences.

Criminal Courts In the USA have tended to accept prosecution

arguments that if no physical evidence of a malfunction

in the cruise control or electronic throttle can be found, the

SA incident must have been caused by driver error. By such

fallacious argument, the burden of proof is reversed, and the


Terms that are used more or less interchangeably are: UA D Unintended

Acceleration, or Un-commanded Acceleration; SA

D Sudden Acceleration.


D Sudden Acceleration Incident.



2014 IEEE. Translations and content mining are permitted for academic research only.

Personal use is also permitted, but republication/redistribution requires IEEE permission.

See http://www.ieee.org/publications_standards/publications/rights/index.html for more information. VOLUME 2, 2014

A. F. Anderson: Intermittent Electrical Contact Resistance as a Contributory Factor

vehicle is assumed innocent unless proven guilty, rather than

the driver.

The main source of SA statistics is the Complaints

Database of the Of ce of Defects Investigation (ODI) of

the US National Highway Traf c Safety Administration


3 The US National Aeronautical and Space Administration

(NASA) in its 2011 Report on SA in Toyota vehicles

[1] analysed all vehicle complaints received by NHTSA

between 2000 and 2010 and concluded that 2.3% could be

identi ed as SA incidents. This equated to a rate of about

1/100,000 vehicles per year for the USA. This statistic hides

the fact that there is wide variation in complaint rate by

vehicle model and model year [2], [3].

Generally speaking the likelihood of an individual driver

experiencing a SA incident in his driving lifetime is very low.

However, if he purchases a particular model manufactured in

a particular model year he may nd that the vehicle happens

to be one of a batch where the incident rate is an order of

magnitude greater than the rate quoted above. There are over

1,000 million automobiles in the world. A SA incident rate of

1/100,000 vehicle per year equates to 10,000 incidents in the

world per year. There is therefore a signi cant public safety

issue that needs to be addressed. But before effective preventive

measures can be devised and put into practice, the contributory

failure mechanisms must be identi ed, discussed

and come to be understood. It is the purpose of this paper to

contribute to this discussion process by focussing attention on

the potential role of vibration-induced electrical intermittency

as a possible contributory factor in SA incidents.



An example of a SA incident from near standstill is recorded

in the NHTSA ODI Complaints Database[ ODI 1049505] and

was captured on high de nition security cameras. The video

clip included in this paper captures the period of 8 seconds

before the start of the incident and two alternating SAs in

forward and reverse directions during the subsequent

22.9 seconds before the vehicle came to a halt.

4 The aftermath

of this incident is shown in Fig. 1. The manufacturer, after

inspecting the wrecked vehicle, downloading the EDR results

and seeing the video, concluded that there was no evidence of

a defect.

The 31 second video provides a detailed record of an

entire low-speed sudden acceleration incident from which

it was possible for the author of this paper to establish SA

durations and impact speeds, as shown in Appendix III. When

he compared the vehicle's speed calculated from the video

with the claimed spot speeds downloaded from the Electronic

Data Recorder (EDR), he found signi cant mismatches


This complaints database allows SA complaints to be reported in free

format under the category of VEHICLE SPEED CONTROL, but does not

allow detailed information about each incident to be gathered in a structured

way that would allow epidemiological studies to be carried out.


Explanation: the driver may have been trying to control speed by shifting

from forward to reverse gear and vice versa.


Aftermath of an alleged double sudden acceleration into a

house captured on video.

5 Whole incident including 8.5 seconds before

start of SA. Second view from start of SA finishing after end of incident.

Third view from above front door with household response.

that could not be explained by measurement error or wheel


The EDR record, see Fig. A3-3, claims to show that

at 4.6 seconds before the initial impact in the rst SA

incident the vehicle was moving forwards at 12.4 mph.

The video recording shows that at this time the vehicle

was moving very slowly and in an apparently controlled

manner and was just beginning to turn into the parking

area. The video shows that the rst SA incident began

less than 2 seconds before the rst impact with the right

hand garage and not at least 4.6 seconds before impact

as the EDR record claims.

The EDR record claims an impact speed of 14.9 mph for

the rst impact with the right hand garage. The author

has estimated from the video that the impact speed was

between 7.4 and 9.3 mph (i.e. between 50% and 62% of

what the EDR record claims).

In the second SA incident, Fig. A3-4, the EDR claims

an impact speed of 22.4 mph with the left hand garage.

The author has estimated from the video that the impact

speed was approximately 12.7 mph. (i.e. approximately

57% of what the EDR record claims).

The speeds calculated from the video appear to be significantly

lower than the spot speeds obtained from the EDR

data and these discrepancies should be borne in mind during

the reading of this paper. How might such apparent speed

discrepancies come about?

The video shows that the engine did not stall on vehicle

impact with the either the right hand or left hand

garage, but the wheels continued to rotate in the forward

direction in a jerky manner until the moment when the

vehicle was put into reverse and started accelerating backwards.

In the author's opinion, this continued development of

torque at the drive wheels after impact and the consequential

wheel slippage is a result of the torque multiplication factor


VOLUME 2, 2014