Automatic speed management systems : great safety potential ? Paper presented at the Fourth European workshop on Recent Developments in Road Safety Research, October 22-23, 1991 at Bundesanstalt für Strassenwesen (BASt) Bergisch Gladbach, Germany.

A description is given of a speed management project in the Netherlands, carried out and evaluated by SWOV Institute for Road Safety Research. The following hypotheses form the basis of the four experiments conducted on two-lane rural roads with a speed limit of 80 km/h: (1) Drivers will comply to the rules, when they know the detection risk to be high; (2) Automatic speed warning and enforcement with a high detection rate, accompanied by an information campaign will increase the attention level of drivers; (3) This will lead to speed behaviour that conforms to the rules; and (4) all these effects will reduce the accident rate. The experiment is set up in the form of a before and after study - the after study was conducted in the period 30 November 1990-30 June 1991 - and consists of the following steps: (i) information campaign; (ii) speed warning; (iii) enforcement; and (iv) a cost benefit calculation. The evaluation was conducted on: (a) speed, whereby in this paper attention is paid to speed measurements of two road stretches; (b) the total number of accidents; and (c) automatic enforcement. The conclusions made are as follows: (1) The problem of road safety on two-lane rural roads can be tackled effectively by automatic speed management. A combination of measures is needed: information campaign, fixed signs, switchable signs and automatic enforcement and speedy processing of the photo's of trespassers; (2) The reduction in average speed on the two locations was small but consistently present, around 2 km/h. The standard deviation showed a relatively larger reduction. The percentage of speeders showed the largest decline, up to one third reduction; (3) Although the period of the experiment was relatively short and so the number of accidents relatively small, the number of accidents on two experimental roads has been reduced considerably. On the two other roads preliminary results show a similar reduction in accidents; and (4) the reduction in the number of accidents might be accounted for by the decline in speed and by a greater attentiveness on the part of the car driver as a result of the information campaign and of the flashing signs. The introduction and evaluation of "time sharing" is recommended. "Time sharing" is the use of the same elements of the speed management system (switchable sign, radar and camera) on two neighbouring road stretches. These elements can be installed randomly on the two roads. This paper was presented at the Fourth European Workshop on Recent Developments in Road Safety Research, Bundesanstalt für Strassenwesen, Bergisch Gladbach, Germany, October 22-23, 1991