Speed Kills - But What Speed?

by Bernd Felsche

First published in the September 1997 edition of ViaWest
the offical publication of the Volkswagen Club of Western Australia (Inc.)
Updated December 2000 to incorporate later statistics.

Although some people would like you to believe otherwise, only a small proportion of road deaths can be associated with exceeding the speed limit.

I was following some links from the Australian official Volkswagen web site and I stumbled across the German Internet site (http://www.bg-dvr.de) of the German Road Safety Council, which amongst the 3000 pages of online data, contains analyses of crash data to provide information which could be used to address aspects of traffic safety on a scientific basis.

The information is presented mostly in German. [Lucky for some!] Some content is translated by the Council to explain what they do, how they are funded, etc.

In summary, German crash data up to 1991 [recently updated to 1998 figures] indicated that only about one in ten crashes causing substantial damage, injury or death, in which excessive speed was a factor, could be attributed to speeds in excess of the speed limit. For those crashes causing death, the proportion rises to about one in five. One could ask how this justifies draconian and unquestioning policing of speed limits.

If Australian crash data are similar, which is not an entirely unreasonable assumption, then aren't we putting an awful lot of resources into something which at best would represent about one in five road deaths? To put it another way; other than policing speed limits (and drink driving), have we seen any concerted road safety campaigns to address the other (majority) of crash causes?

Cynical observers conclude that the other, perhaps 70%, are too hard to police. It's easy to setup a booze bus or a Multanova, and in the latter case it can certainly be financially lucrative. Resources absorbed in doing things the easy way, means that they can't be used to perhaps greater effect to do the hard things.

So perhaps it's then not surprising to see a rise in the road toll in Western Australia as the vigour of policing of speed limits has increased. I've translated some extracts which are of an especially educational nature. How you use this information is up to you. For your own safety, keep in mind that inappropriate speed kills and 80% of the time, that is at speeds below the speed limit.

You, as the driver, need to judge what is an appropriate speed and you are in the best position to judge what's appropriate. To become a better judge of what's appropriate, you may like to look at an advanced driving course. The good ones will anhance your ability to make an assessment of risks so that you are at a speed appropriate to the situation. Although the RAC (WA) has recently seemingly argued against advanced driver training; stating that participants in the training have more crashes, that "statistic" is rather vague as it doesn't state the rate of crashes/distance covered or time on the road. The RAC reasons that the crashes are caused by the drivers taking more risks because of an increased level of (false) confidence.

One can only question as to what sort of advanced driver training was undertaken, and if those having all the crashes actually graduated. If crashes are happening to graduates of the courses, then surely the RAC should adopt a more positive position and help to establish minimal standards for advanced driver training.

Bernd Felsche

Translated excerpts from http://www.bg-dvr.de

1 Speed-Related Crashes

1.1 Statistics

Statistics relating to speed-related crashes contain several inaccuracies.

Statistics are based on figures collected by the Federal Bureau of Statistics. These figures include several inaccuracies resulting from the way in which data are collected. Data collected by the Police form the core of information. Crashes which did not cause significant damage, and hence did not result in a Police report, therefore do not appear.

Traffic deaths include those who died within 30 days after the crash as a result of injuries sustained. Severe injuries are those which caused admission to a hospital for a minimum of 24 hours. All others count as light injuries.

The cause of an crash is determined by the Police officer attending the scene of the crash. In doing so, the officer uses a special form for that purpose. The cause "speed" appears as only a single entity in the collected statistics; but not as "inappropriate speed". Other crash causes are dependent upon speed; e.g. overtaking and following distance.

Only one crash cause is attributed per vehicle, with a limit of three per crash.

1.2 Crash Causes

Inappropriate speed is the most likely cause of crashes.

1.3 Severity

Every second traffic fatality is due to inappropriate speed. [But see 1.9]

1.4 Inside and Outside Localities

More speed-related crashes occur outside of localities than within. [comparable to built-up areas in Australia]

1.5 Vehicle Types

Passenger cars are primarily involved in speed-related crashes.

1.6 Ages

Young drivers cause a disproportionately high number of speed-related crashes.

1.7 Sex

Overall, women appear to be less likely to be involved in speed-related crashes than men.

1.8 Autobahn

Inappropriate speed is slightly more likely to be the cause of a crash on the Autobahn than average.

1.9 Exceeding the Speed Limit

Only about one in ten of all speed-related crashes is associated with exceeding the speed limit.

Although exceeding the speed limit is a significant factor, it is not a dominant one. In proportion to all speed related crashes causing death, only about one in five can be attributed to exceeding the speed limit.

[Figures in this table have been combined by Bernd Felsche for illustration.]
Crash Consequences and Exceeding the Speed Limit 1990/1996 (percentage of all speed-related crashes)
death22.6/17.6 8.5/5.914.1/11.7
injury13.2/10.0 7.5/5.25.7/4.8
Substantial damage11.6/10.5 7.0/5.84.6/4.7

6.4.2 Braking Distances

A vehicle must be retarded to come to a standstill. Braking distance is that distance which is covered from the commencement of retardation to standstill.

Retardation is defined by negative acceleration; i.e. the rate at which speed is being reduced. This is measured in m/s2. Measurements of average drivers in practical situations indicate a median (not maximum) retardation of about 4 m/s2. It is technologically possible to achieve a median 8 m/s2. Numerous test have indicated that very few drivers are capable of braking so heavily in an instant. The StVZO [vehicle standards regulation] requires a median retardation of 2.5 m/s2.

7.6 Automatic Anti-Lock Brakes

Anti-lock braking systems are becoming more common.

Unfortunately, less than 30% of the owners of vehicles equipped with such systems, actually know how to use them appropriately. It is often incorrectly assumed that the braking distance will be reduced as a function of the system. The gain in safety is in avoidance and braking in an emergency stop. Many drivers mistakenly believe that a reduction in braking distance was the significant function of the system. This lack of information and understanding can lead to situations where drivers follow too closely and negate any benefit provided by the system.

(Source: F. Nicklisch 1992)