Do you respond to an impending collision in the same way as you respond to a traffic signal?

That question is being examined through research by Gorski Consulting. In the past fews years vehicles stopped at traffic signals have been videotaped with a dash camera in the short instance when the traffic signal turns from red to green. The observed delay is used to explore how drivers might react to similar stimuli in the short seconds before a traffic emergency.

Researchers have found it difficult to explore the reactions of drivers to emergency situations because, in order to do so, the driver must be placed in a realistic emergency situation and that could be dangerous. Recent advances with advanced simulators have made environments that appear very real and thus better data on perception-response delays are gathered. Unfortunately such simulators are extremely expensive and rare and used by only a handful of research facilities.

The Gorski Consulting research is simple and extremely cost effective. An inexpensive dash camera is used to create the video and these segments are inserted into a low-cost video-editting program. This allows a frame-by-frame study of the instant that a signal changes and the time when a vehicle’s brake lights extinguish.

This data will also be used to examine the reaction times of drivers at specific intersections to determine if the layout of the intersection makes a meaningful difference in response delays. Other factors such as the influence of other drivers will also be examined.

Preliminary results demonstrate the complexity of some responses. While we would believe that the response to a traffic signal should be relatively simple, some subtle nuances become revealed through detailed study. It is interesting how drivers will release a brake pedal slightly so that the vehicle begins to crawl forward while the brake light remains illuminated.

Also very short response delays have been observed. While delays in the range of 0.6 to 0.8 seconds could be expected, many delays are below 0.5 seconds. Presently these very short delays seem puzzling as drivers should not be capable of reacting in such short times to an emitted stimulus. Driver pre-processing of their environment and “guessing” that a signal may soon change could be an explanation for these results.

We are also observing very long delays suggesting that these drivers are not attentive to the traffic signal. This may be relevant to the issue of driver distraction.

This work is also being conducted to explore the rather simple conclusions drawn by many in the collision reconstruction community who testify in court about what a driver should have done to avoid a collision. The behaviour of humans in a complex environment cannot be narrowed to these simple conclusions as many factors affect the relationship.