The total number of personal injury accidents has decreased in recent years, but accidents of the rear end collision type have increased. This project is meant to elucidate how it would be possible by means of information and surveillance to induce drivers to maintain a safer distance from the vehicle in front. A survey was first made in the form of a study of the literature, an accident study and an interview survey. In the literature study, rules for distance keeping and descriptions of various experiments were found. The accident study showed that most rear end collisions occur in towns and near intersections. Of the interviewed drivers, 20-30% had been involved in rear end collisions, 3/4 thought that the 3 second rule was good, but only 1/3 used some kind of distance rule. It was decided that in the experiment three different measures would be investigated on four different sections, three in urban traffic and one in rural conditions. The measures would then be extended in three stages. The first stage would involve the use of signs asking drivers to keep their distance. In the second stage this would be augmented with information giving the appropriate distance. In the third stage, police surveillance would be used at the same time. The methods were: (1) distance markings in the form of chevrons painted on the carriageway; (2) electronic sign that measured and stated the distance from the vehicle in front; and (3) the use of post delineators as distance measurement. It was decided that two seconds were a suitable distance in towns. The chevrons were therefore painted so that the distance between two chevrons corresponded to a time gap of 2 seconds at the speed given by the speed limit. On rural roads the post delineators were already installed at distances of 60 m which corresponds to a time gap of 2.4 seconds at the 90 km/h speed limit. The results show that the proportion of impeded cars which have a time gap shorter than 2 seconds was reduced by: (1) 5.6 percentage points to 51.5% on the 50 km/h street with the chevrons; (2) 9.3 percentage points to 48.3% on the 70 km/h urban expressway with the chevrons; (3) 12.6 percentage points to 32.0% on the 50 km/h street with the electronic sign; and (4) 5.2 percentage points to 54.2% on the 90 km/h rural road with post delineators. Police surveillance produced a further reduction by 0.6 percentage point on the 70 km/h expressway and by 1.7 percentage point on the 90 km/h road. In an interview after the experiment, 39% stated that they had increased their distance. (A)
Samenvatting