LOOKING AHEAD: SPEED LIMITERS
In-vehicle speed limiters have substantial potential for enforcing speed limits. One type has been in use since March 1988, when British and European legislation made it compulsory for speed limiters to be fitted to almost all coaches and to most heavy goods vehicles. Some lorries and most coaches are limited to 60mph, but this only addresses top speeds and can therefore only enforce the speed limit on motorways (Plowden and Hillman, 1996).
With a variable speed limiter, however, the speed at which the limiter starts to take effect can be altered. This makes it possible to use the limiter to enforce the speed limit on all classes of road.
Variable speed limiters can be either externally activated or operated by the driver. Externally activated limiters are triggered by a radio signal which can be transmitted from equipment installed at the roadside or under the road, or (the method favoured by DETR and the EU) from a satellite. With a driver-operated limiter, the driver sets the limiter at or below the speed limit of the road on which they are driving. Conspicuously positioned colour-coded lights, for example on the front and rear windscreens, would indicate within which band the limiter had been set.
With externally activated speed limiters, speed limits would become entirely self-enforcing. For the driver-operated speed limiter, the external lights would make enforcement much easier than at present. Driver-operated limiters could, however, be introduced much more quickly than externally activated speed limiters. Perfecting externally activated limiters may require years of research, but driver-operated limiters rely on the same technology as cruise control, which is already thoroughly established.
There is, indeed, no technical reason why speed limiters could not be included in all new cars as of now, adding around £40 to the manufacturing cost. This compares to £2,000 estimated for the type of variable speed limiter now being developed for the DETR by the Institute for Transport Studies at Leeds University (a cost expected to fall to around £360 per vehicle by 2010, when the road maps necessary for the satellite system to work should be standard in most cars). The advantage of an externally activated limiter over a driver-operated one would have to be substantial in order to justify a cost difference of £300 per vehicle and a delay of 10 years, given the thousands of deaths and injuries which could be prevented during that time.
The Parliamentary Advisory Council for Transport Safety (PACTS) has recommended that DETR, the Department of Trade and Industry and European authorities work together on the development of variable speed limiters. They should, PACTS recommends, promote further research, including field trials, into long-term behavioural changes as well as levels of public acceptability and concern over speed limiters (PACTS, 1999).
8.2 European MASTER Project speed limiter field trials
As part of the European MASTER Project (Managing Speeds of Traffic on European Roads), field trials were carried out in Sweden, Spain and the Netherlands using cars with on-board speed limiters which ensured vehicles could not exceed the speed limits posted. The trials were carried out in order to investigate driver reaction and acceptance of an in-car speed limiter. Between 20 and 24 drivers per country drove twice along a test route, once with the limiter off and once with the limiter on. The length of test route was 20-30km, consisting of an urban street network, rural roads and a length of motorway.
The speed limiter reduced mean speeds significantly on all types of urban roads with speed limits of 30, 40, 50 and 60kph speed limits. On rural roads the speed limiters were only effective in reducing mean speeds on 70kph speed limit roads in Sweden. On other stretches of roads (with speed limits of 80 and 90kph) no significant effect could be found. The researchers suggested this was due to traffic volume on these roads, with frequent platooning of vehicles.
Having considered the results of this field trial and other research on speed limiters, the European MASTER Project recommended: "Preparation for the introduction of compulsory adaptive speed limiters should be started" (MASTER Project, 1999).
Most powers of vehicle regulation have now passed from individual countries to the European Commission, and this poses a potential legal obstacle to the introduction of variable speed limiters. However, EU member states have retained some powers to legislate independently on matters affecting safety. This might enable the UK to introduce speed limiters independently, or to ask leave to do so on the grounds that trials by one member state would be in the interests of all.
Legislation would set a date from which all new vehicles would have to be equipped with driver-operated variable speed limiters. A second date would be set from which all drivers with in-car speed limiters would have to use them. Owners of cars already on the road could be encouraged to retrofit speed limiters, for example through a temporary reduction in Vehicle Excise Duty (experiments in Germany in the late 1980s suggest that retrofitting would cost around £250 per vehicle).
There would eventually be
a legal obligation on drivers to set limiters to the prevailing speed limit,
but control would remain in the driver’s hands. A driver-operated speed
limiter would also allow the driver to break the speed limit in an emergency.
MASTER Project (1999) Managing speeds of traffic on European roads, Transport Research, Fourth Framework Programme Road Transport, Luxembourg: Office for Official Publications of the European Communities
PACTS (1999) Road traffic law and enforcement: a driving force for casualty reduction (summary), London: PACTS
Plowden, S and Hillman, M (1996) Speed control and transport policy, London: Policy Studies Institute