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Cameras at intersections lead to sudden braking and short following distances    Mar 02, 2018

Cameras at intersections lead to sudden braking and short following distances
Mar 02, 2018


dr. Evelien POLDERS



Speed and red light cameras provide shorter following distances and brighter brake moments at intersections. An undesirable side effect that (perhaps) lies at the basis of the increasing number of rear-end collisions. This and more is shown by research by Evelien Polders (Transportation Research Institute) about road safety at intersections. Dr Polders recently obtained her PhD title at Hasselt University.

Intersections are considered to be one of the most dangerous and complex locations in the road network. “That is why it is so important to improve the road safety at these spots”, says Dr Evelien Polders. For her PhD, she investigated the road safety of intersections, not only by just analysing accidents, but also the behaviour of road users and serious conflicts that lead to near-accidents.

“In concrete terms, I focused on four subjects: accident patterns on roundabouts and on intersections with traffic lights; behavioural adjustments of drivers to speed and red light cameras on traffic-lighted intersections; and to the extent to which the difference in priority rule – right of way from the right versus priority-crossing – affects traffic safety and behaviour of drivers.

Abrupt brakes
The most striking result of the study is that speed and red light cameras at intersections cause a decrease in the number of drivers who still cross over to orange or red, but at the same time, this leads to shorter following distances and abrupt braking movements. Evelien Polders: “Earlier research has already shown that the number of rear-end collisions at traffic-lighted intersections increases after the installation of such cameras. Explain this in addition to the results of my research, and you get a possible explanation for the increase in this type of accident.”

In addition, four dominant types of accidents occur at roundabouts and traffic-lighted intersections. “For traffic-lighted intersections, these are rear-end collisions, side and frontal accidents, and accidents involving at least one vulnerable road user.”

The results formed the basis for policy recommendations given higher road safety at intersections. “You can reduce the unwanted side effect of speed and red light cameras by warning drivers when they approach an intersection with an unmanned camera”, says Evelien Polders. “And conflict-free traffic lights at intersections have a positive effect on the general safety at intersections – and on the number of accidents with vulnerable road users in particular.”