For anybody who has not had direct experience of such a horrendous event it is impossible to truly understand the horror and grief felt by the families of those who were killed on that day.
Unfortunately the English criminal justice system failed to help the families understand what had lead to these deaths, something that may help them in their grief. Nor, importantly, did it do what it should have done to help prevent further accidents of this type. This is because the judge ruled that the scientific explanation of the cause of the accident was inadmissible in court and could not be put to a jury.
So what is this scientific explanation for these ‘unintended acceleration accidents’, which have been known of in the fields of road safety and human psychology since at least the 1970s? The first point to make is that they are not due to a fault with the vehicle. The reason the vehicle initially accelerates very fast is that the driver, needing to make a rapid application of the foot brake, actually presses the accelerator pdal instead. This is due to a foot aiming bias at the time the foot movement is initiated which in turn can be caused by upper body twist such as looking over the shoulder to operate hand controls, check the road is clear when pulling out or attending to passengers who have boarded the bus. The accelerator and brake pedals in buses can be very similar in shape, height and angle so the only way of distinguishing them is by their position and the foot aiming bias effectively eliminates this cue.
When the driver then presses down hard on the (accelerator) pedal, believing he is applying the brakes the bus suddenly and unexpectedly accelerates forward. This is startling to the driver, and the immediate risks of collision with other vehicles and pedestrians can evoke the panic state of ‘hypervigilance’. In this state the individual’s focus of attention is narrowed and his ability to process information and make decisions can be disrupted. The driver’s attention may be so focussed on the scene through the windscreen and steering the vehicle to avoid collisions that he is unable to detect his foot is on the wrong pedal or to plan and undertake any other action to bring the vehicle to a halt in the time available. Indeed drivers typically continue to insist, when interviewed after the accident, that their foot was on the brake pedal and that the vehicle simply ‘surged’.
There is only space here for this very brief summary of the cause of such accidents (a fuller account is given by the paper by Schmidt, who developed the explanation). It is however based on a review of extensive laboratory and real life research involving typical people, and scientific understanding of the manner in which the brain controls limb movement. The implications of this explanation are that, in the right circumstances, anybody driving an automatic vehicle, such as a bus, could experience this type of accident. It does not imply any failure on the part of the driver. It should also be noted that no other scientific explanation of these accidents has been proposed.
However, in English law, there are only a finite set of defences to the charge of causing death by dangerous driving and in this case the judge ruled that this explanation did not fall within any of them and therefore could not be put to a jury. At this point the driver had not option but to plead guilty. The judges’ opinion, rather than a jury, informed by objective scientific evidence, had therefore decided this case.
In passing sentence the judge stated “It is difficult to imagine a more serious single example of your dangerous driving…..” I would suggest the judge has a look at some of the many previous accidents I have had to investigate, including the similar fatal case in Sunderland in 1998.
Finding the driver wholly and solely guilty severely reduces the incentive for measures to be found to prevent future accidents of this type (e.g. modifications to vehicles, driver training) and does nothing to improve public safety.
The severe penalty imposed by the judge on the driver will cannot deter other drivers from committing this crime: they do not do it deliberately or due to lack of care, or under the influence of fatigue, drink or drugs etc.
So, other than reacting with pious retribution, just how has the justice system served the people in this case? I sit here with a feeling of foreboding, as I did after the Sunderland accident, waiting to hear of the next fatal unintended acceleration accident, which the criminal justice system could have helped avoid. Meanwhile a bus driver, guilty of no more than being human, must endure a five-year prison sentence on top of the lifetime of anguish from the horror he experienced on that dreadful day.
Reference
Schmidt, R. A. Unintended acceleration: Human performance considerations. In Peacock B and Karwowski W (Eds) Automotive Ergonomics. Taylor and Francis 1993.
Comments
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Unintended acceleration
28.11.2005 10:46
Melvyn Danielson
e-mail:
melvyn.danielson@ntlworld.com
Design flaws and responsibility
28.11.2005 18:49
Just as in operating any other piece of heavy machinery, the guy had been trained, should have been aware of the pitfalls and ultimately its his responsibility. The sentence is way too steep - it should have been a driving ban and 6 months - at the most. The sentence should always reflect the offence not the consequences - something some judges seem to forget.
Roger S
e-mail:
roger@derbysabs.org
Homepage:
http://www.derbysabs.org
Brake vs Accelerator
29.11.2005 10:19
Its natural for an observer to assume that the error must simply be the use of the accelerator instead of the brake. I say that under those circumstances a driver would realise the error immediately and by reflex remove his foot from the pedal. The misrepresentation of the phenomenon of 'unintended accelertion' will only perpetuate the problem.
A device giving supremacy to the brake must be a sound proposal don't you think?
Melvyn Danielson
Some additional info
30.11.2005 17:29
There is a partial solution which is installed on some buses and that is an interlock which prevents the driver selecting a driving gear from neutral unless the brake pedal is pressed. This is not a total solution however because: -
1.some accidents happen when the bus is already moving and
2.it depends on the driver selecting neutral when pulling up at bus stops, and some bus companies discourage this. In fact some gearboxes have a false nuetral which is automatically selected when the bus stops, but still only requires the driver to press the accelerator for Drive to be re-selected.
This brings me on to the issue of the driver being trained and therefore somehow responsible for the accident. If the driver is not trained to always manually select neutral, and it seems at that they are not, the interlock system is rendered ineffective. Additionally, now that this type of accident is known about it is important that drivers are informed of the causes. The initial 'surge' due to accidental accelerator pedal operation may they be less starling to the driver and he/she will be able to identify the error immediatelty and bring the vehicle under control.
And finally, these accidents are not due to the driver pressing the brake and accelerator pedal at the same time. If this is done the braking system has sufficient power to stop the vehicle when both pedals are pressed simultaneously.
Dean
Brake vs Accelerator
01.12.2005 13:42
Rather than a test to prove it possible to stop a vehicle, I would like to see a detailed investigation in which manufacturers establish the parameters under which the brake pressure would be 'insufficient' to overcome the torque of the engine. Once these parameters are found, it would be interesting to find out how they compare with 'normal' driving behaviour. In other words, in a crisis situation up to what point could a driver be expected to increase pressure on the brake whilst at the same time experiencing acceleration?
Human frailty, human frailty....
Mel Danielson
Human error - how do you overcome this?
03.03.2013 19:34
The facts are:
Many buses/coaches will not allow the accelerator to be applied at the same time as the brake pedal (the accelerator switches off as soon as the brakes are applied).
On older vehicles where this does not apply the engine is usually powerful enough to overcome the brakes.
Accidents do happen after neutral has been selected. When a driver wishes to reverse from a bus stand and selects drive by mistake, as soon as the park brake is released the bus will move forward thus confusing the driver who can then press the accelerator in error demolishing anything in its path. I have witnessed this on three separate occasions.
There are many more examples but unfortunately the problem remains. Human error, how do we combat it?
I am not sure if there is a simple answer. One answer that I do have however is the little box of electrics that I have developed to aid the driver and help prevent foot misplacement error. It is currently in service on trials with a large bus operator and all being well will be retrofitted across the country.
The aim of this device is to save innocent lives and protect the driver from something he/she has no control over.
If this saves one life...we have won.
Vince Thompson
e-mail:
vince776@sky.com
Homepage:
www.diagtest.co.uk