The Car Bibles - Separating the fact from the fiction about speeding and speedtraps.

Speeding facts vs. fiction

Why this page?

So why talk about speeding in a site dedicated to information about car maintenance. Well predominantly to illustrate a point about anti-lock brakes in the Brake Bible but also to show how car maintenance overall plays into accidents in surprising ways.

Speeding - the emotive issue.

A long time ago, I ran a site called the Speedtrap Bible; its purpose was to educate the public about the technology invoked by the police to catch and prosecute people for speeding. Some thought the site was the saviour of drivers, whilst others pretty much directly accused me of single-handedly promoting child murder. Speeding - it's an emotive issue and one which the police and government always use as leverage whenever they get a chance. Constable Tim NiceButDim, when interviewed next to a smouldering pile of twisted metal on the side of the M25 will say "This accident was caused by people speeding, plain and simple." Similarly, Highway Patrol Officer Chad SteroidAbuse, when interviewed next to a smouldering pile of twisted metal on the side of Interstate 15, will say "This accident was caused by excessive speed and nothing more." It's the same the world over, but separating actual fact from emotive fiction is always difficult. As part of my research when authoring the Speedtrap Bible, I spent a day at the Transport Research Laboratory in Crowthorne, in England. It's the government's vehicular research centre, with high speed test tracks, crash rooms, drag strips, banked curves and all manner of other test areas set in the lush forests around Bracknell in England. They test everything there from the effectiveness of seatbelts inside a car to the effectiveness of road surfaces and crash barriers outside the car. I was particularly interested in their studies on speed in relation to the cause of accidents. The library at the TRL has copies of all their reports, and the two I spoke to their technicians about (and ended up buying) were TRL323 entitled "A new system for recording contributary factors in road accidents" and TRL325 - "The factors that influence a driver's choice of speed."

Is speed a contributing factor in most road accidents? TRL323

The short and politically incorrect answer is no, and here's why. TRL Report 323 entitled "A new system for recording contributary factors in road accidents" was a joint project between the TRL and the DETR (Department of Environment, Transport and Regions). It was designed to give true figures for the real causes of accidents taken across 8 representative police forces over 6 months in the summer of 1996. They devised a system based on two main categories: what went wrong, and why? Each of those is divided into subcategories such as failures of the driver or rider, failures of pedestrians etc. The report is a fascinating read for someone like me who has a website to maintain, but could be incredibly dull to most people. So to cut to the chase, there's two sections of information we need to look at.

1. Overall incidence of contributary factors
This is a categorised list of all the factors in the report which could contribute to but not necessarily cause an accident. I've reproduced the top 5 items from the report here:

All factors involved in accident Definite factors involved in accident
Description Number % Number %
Failure to judge other person's path or speed 623 10.7% 218 10.3%
Behaviour - carelessness / thoughtlessness / recklessness 513 8.8% 210 10%
Inattention 465 8% 130 6.2%
Looked but did not see 436 7.5% 149 7.1%
Excessive speed 424 7.3% 126 6%

What this means is that in 7.3% of the accidents, speed was one of many factors, and in only 6% of the accidents was it a definite causal factor. Look at the top 4 factors and you'll see that they can generally be categorised as the old police adage of "driving without due care and attention." More to the point, if you take into account "loss of control" accidents (which covers a multitude of sins including wheels coming off the vehicle, black ice, etc) then according to the report, only 4% of all accidents are caused by loss of control of the vehicle with excessive speed as the primary contributing factor.

2. Incidence of commonest precipitating factors, by type of accident.
This is perhaps a more telling chunk of information which aims to show the most common factors involved in different types of accident, such as vehicle-pedestrian, single-vehicle etc. Excessive speed doesn't feature directly in this information because it is considered to be a subcategory of "loss of control" (see above). The government and road safety campaigners will always tell us that pedestrians are killed because of speeding motorists. This simply is not the case. Would you believe a staggering 84% of pedestrians involved in accidents are killed or seriously injured due to their own incompetence? In the TRL report, the prime factors involved in pedestrian fatalities are listed as:

So in the real world, it's not motorists tearing up and down town centre roads at speed that is to blame for pedestrian fatalities, but the pedestrians themselves for stepping in front of moving vehicles without bothering to look where they're going. This simple fact alone explains the push in current car design to make more pedestrian-friendly front ends for vehicle. If you can't stop the idiots from blindly wandering into the road, then you need to try to damage them as little as possible when you inevitably run them down.
An amusing little sub-note for you here - another report further subcategorises "entering the carriageway without due care", and shows that after dark, 77% of all adult pedestrian fatalities are caused when the pedestrian is above the legal drink-drive limit - ie. is technically classified as drunk - and staggered into the path of an oncoming vehicle.
For other types of accidents, the "loss of control" figures were as follows:

Remember that "loss of control" covers a wide variety of factors. Excessive speed contributes to only 4.04% of all "loss of control" accidents.

On a side note, there's one other grouping of figures which makes for a good read too. It's not technically to do with speeding, but I'm going to include it here so you can see the other sorts of statistics that TRL323 assembles. This one particular section is headed "Attribution of precipitating factors in accidents which involved one car and either a pedestrian or one other vehicle." In other words, where a car was involved, what percentage of those accidents were actually attributable to, or caused by the car?

If you've read my bikes page then you'll know I also own a motorbike and enjoy riding it. I just thought it was an interesting figure that 90% of all motorbike-to-car accidents were caused by the car. And I bet the most common excuse was "didn't see you mate".....

speed limit 200mph

Will reduced speed limits reduce accidents? TRL325

TRL325 - "The factors that influence a driver's choice of speed." This is another TRL report which I bought and had a good old look through. It's a survey of 5080 drivers in an effort to find out what factors contributed to them speeding in the first place. More importantly it also looked at the correlation between speed and accidents and asked the question: if you drop the speed limit, does the accident rate go down?
During this study, TRL determined that there were many causes of "speed variation". These included:

By grouping these factors and arranging them in order of importance, these become:

  1. Site effects. This includes things such as people's estimation of their speed based on the geometry of their surroundings. ie. you might be used to associating a certain frequency of seeing lamp posts with a certain speed. In a new area, the lamp posts might be further apart, but you're trying to maintain the frequency of site geometry that you're accustomed to, thus driving faster without realising it.
  2. Driver effects: age, sex and exposure. This includes things such as how often you drive, and how far you drive.
  3. Psychological variables. This includes things such as modern cars being quieter and more comfortable than older cars, thus making it more difficult to determine the speed you are going without glueing your eyes to the speedometer. It also includes factors such as "do you own the car?" - people are more inclined to speed in company cars because the psychological factors tell them the vehicle isn't their responsibility.

So what does all this mean? Well, it means that there's not one single feature that causes people to speed. You cannot arbitrarily drop the speed limit, bung up a camera and expect people to slow down. It simply does not work. More to the point, the last paragraph of the report sums up the entire study of why people speed, and how speed is related to accidents:
By using predicted speeds as an explanatory variable in the model of accident involvement it is possible to obtain an apparent relationship between speed and accidents. This relationship suggested that a 1% change in an individual driver's choice of speed is associated with a 7.75% change in that individual's accident liability. This 'elasticity' is much greater than that observed between changes in mean speed and accident change on a specific section of road. Of course, the fact that there is an apparent strong "cross-sectional" association between between speed and accidents does not necessarily imply a causal link between the two, and it cannot be assumed that reductions in speed by a particular driver will result in any accident reductions of a size predicted by this association. The association arises from the fact that both speed and accidents are related in similar ways to the same variables - particularly age, experience and exposure.

Speed Cameras Save Lives - the other great lie. TRL595

As a side note, it's worth talking here about another TRL report that was commisioned by the UK government and then quietly hushed up when it too failed to support the 'speed kills' mantra.
TRL595 makes for some jolly interesting reading. It is a motorway safety performance study carried out on behalf of the Highways Agency between November 2001 and July 2003. The phrase most often touted about this study is this: "The study showed that there was no significant difference in the rate of Personal Injury Accidents when road works were present." That is in fact entirely true, but one of the things this report also looked at was the presence of speed cameras and their effect on accidents. And this is where it gets interesing. In England, for as long as I can remember, the government have insisted that speed cameras reduce accidents. They insist that cameras are only put in at accident blackspots. Driving groups and individuals like me have always argued that speed cameras are only ever installed to make money, and this belief has always put us at odds with the government's hard line. I was once served with a cease and desist order against my old website (The Speedtrap Bible) by the department of transport, West Sussex police and Thames Valley police. They claimed that by giving out technical information on the operation of different speed monitoring devices, as well as their locations and how to fight speeding tickets, I was essentially putting drivers in danger because (and here's the mantra again) "speed kills and you are condoning speeding."
So TRL595 and speed cameras - what's the big deal? I'll give you the executive summary first:
At 29 major motorway and road works sites, recording Personal Injury Accident details for an exposure of 4,176 million vehicle kilometres:

  1. GATSO-style wet-film speed cameras increase the accident rate at road works by 55%
  2. GATSO-style wet-film speed cameras increase the accident rate on open motorways by 32%
  3. SPECS-style digital speed cameras increase the accident rate at road works by 4.5%
  4. SPECS-style digital speed cameras increase the accident rate on open motorways by 6.7%

There is little statistical error in those numbers - 18 months and 4,176,000,000 vehicle km is, in statistical terms, a bloody huge sample set. The conclusion of this particular section of the report was "The non-works with speed camera PIA rate is significantly greater than the without speed camera rate."
For the anal-retentives amongst you, here is table 3.18 from TRL595 reproduced in all its glory.

PIA'sMillion vehicle kmPIAs
Without speed cameraWith speed camerasWithout speed cameraWith speed camerasWithout speed cameraWith speed camerasRatio
WorksNon-worksWorksNon-worksWorksNon-worksWorksNon-worksWorksNon-worksWorksNon-worksWithout speed camerasWith speed cameras

How do you get the increase in accident rate out of that table? It's pretty easy. Take a look at the PIA figures for analogue type cameras on open motorway (highlighted in bold). According to the report the accident rate difference in 'non works' areas between those without cameras and those with is 0.089 to 0.117. Some elementary maths to calculate a percentage difference between those two figures gives you 0.117 / 0.089 which is 1.3146, or a 31.46% increase.

The 1997 Parker Study

In 1997 a report was commissioned where speed limits were randomly increased and decreased all over the US to see what effect it would have on accident rates. Overall, drivers did not change their average speeds. What was interesting was that the lower the speed limit, the higher the accident rate, and the higher the speed limit, the lower the crash rate. This isn't a statistical anomaly either - it's not like we're talking about being within one or two percent.
If you want to read the report, it's here, entitled Effects of Raising and Lowering Speed Limits on Selected Roadway Sections - the 1997 Parker Study. It perfectly encapsulates why road and vehicle design, and driver training, have far, far more of an impact on accident rates than arbitrarily imposed speed limits.

Speed differential is a big problem

Following on from the Parker Study, it's been observed time and again that it's the speed differential that is the problem. If you put the speed limit at 100km/h when most people are doing 120km/h, the differential between law-abiding drivers and everyone else is 20km/h. If you raise the limit to 110km/h, the faster drivers don't go even faster - they tend to stay around 120km/h - but now the law-abiding drivers are doing 110km/h, reducing the speed differential to 10km/h
This has be proven in plenty of places around the world. For example vast stretches of I-15 between Utah and Arizona had the limit raised from 70mph to 80mph and the crash, injury and fatality figures fell noticably.

Speed cameras vs. drivers - the escalating arms war.

Reports like TRL323, TRL325 and TRL595 do put a bit of a fly in the ointment when it comes to the official line that "speeding causes accidents". Despite the facts, the police and local governments continue to try to strengthen this myth, and use it as their excuse for installing speed cameras. The simple truth of the matter is that speed cameras don't reduce accident numbers - they nothing more than a method of earning more revenue from unwary drivers. So as new technologies come out to trap motorists, so too do new technologies come out to help them evade the traps. First the police had radar guns, so the motorists got radar detectors. Then the police got laser guns, so the motorists got combined laser and radar detectors. Then the police got speed cameras which were hard to detect with radar detectors, so the motorists got GPS devices with built-in locations for all the cameras. This ridiculous and escalating arms race is all because those in power refuse to admit that they're wrong, and for as long as this situation exists, we, the drivers, will be forced to deal with more and more so-called safety aids in our cars. The ultimate outcome of this is that drivers are dumbing down because they're now expecting their vehicles to be responsible for avoiding accidents, because we're all being fed a constant lie about traffic accident causes. It's a sad cause-and-effect but to quote Al Gore, it's an inconvenient truth.

This video says it all: Speedking kills your pocketbook

Please, please, please watch this. It's from Canada, but it is highly relavent to the US, Australia and most countries in Europe too.

Blaming the motorist for everything

pedestrian culling

In case you hadn't figured it out by now, I'm very pro-car and pro-motorbike and totally against the motorist being blamed for everything. Where I live in Utah, there's now a campaign to make drivers solely responsible for mowing down pedestrians who wander out into traffic without looking. That's totally the wrong message, in my book. It places all the burden on the driver to avoid a pedestrian, rather than making the pedestrian responsible for their actions. Things would be different if they all used pedestrian crossings, but they don't - the wander out into traffic like lemmings and get themselves injured and killed on a daily basis. They don't seem to understand that the road is for cars and the pavements (or sidewalk) is for pedestrians. This current campaign makes as much sense as allowing car drivers to drive on the pavements and making the pedestrians responsible for damaging cars in the ensuing carnage (pun intended). Actually, maybe we should drive on the pavements - there seems to be less chance of hitting a pedestrian there. Once again though, ridiculous campaigns like this play into the hands of car manufacturers who will tell you that ABS would help in a situation like this, and once again we're burdened with more 'safety' devices we don't need. This inattentive pedestrian thing is so epidemic that in Europe now, cars are being manufactured to be pedestrian-friendly - to damage them less when you hit them. Another classic case of treating the symptoms of the problem rather than the cause. The picture on the right shows one of the campaign posters on the back of a bus, taken by a passenger in my car with my crappy cellphone camera.

Conclusion : Speeding isn't the problem.

So speed doesn't kill. Well - it does - but in nowhere near the numbers we're told and not in the way the authorities would like you to believe. It's common sense that higher speed will make any accident more violent, but higher speed does not cause the accident in the first place. The police and governments should be spending more time on educating people to drive properly and pay attention - less loss-of-control or inattention accidents would be the result of that. They should spend more time making pedestrians responsible for their own actions instead of blaming drivers. That would reduce the pedestrian culling. They should spend more time and resources banning cellphones and arresting drivers for drunk and drugged driving - all major causes of accidents as supported by dozens of reports. But speeding remains the lowest fruit in the tree and consequently the easiest one to pick, even though it's the single least responsible line item for the cause of accidents.

All interesting reports then. I'm not saying they're gospel, but I am far more prepared to believe this type of study than I am prepared to believe politicians. According to these reports, speed is neither a contributing nor definite factor in the majority of road traffic accidents. Nor will reducing vehicle speeds necessarily lead to any reduction in accident rates.
There's an interesting UK parliament memorandum on this very topic that you can enjoy for further reading here: Memorandum by The Association of British Drivers (RTS 11)
I've also created a PDF of that page in case it conveniently disappears. You can download the PDF here.

Thanks to the TRL for an interesting day out, and the TRL's library and publication services for helping me to find and purchase TRL323 and TRL325 reports.

You can find many of their reports online for free now at the TRL documentation library.

And finally....

From an unknown source, doing the rounds on the internet:

speeding - what's your excuse?


Links to the various reports and others from the TRL. All publication ©Transport Research Laboratory.
TRL323: A new system for recording contributory factors in road accidents
TRL325: The factors that influence a driver's choice of speed
TRL421: The effects of drivers' speed on the frequency of road accidents
TRL440: The characteristics of speeders
TRL595: Safety performance of traffic management at major motorway road works