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By Jordan W. Charness

It seems that there are studies for just about everything these days; there was even one that researched drivers’ behaviour when they approached yellow lights. Recently, the American Society of Highway Engineer’s National Conference heard a presentation of a study that was funded by the Ohio Transportation Consortium and Ohio Department of Transportation. It observed 1,572 vehicles at four intersections to find out exactly how people reacted in that split second when the light turns from green to yellow.

Before I go into the study, let’s review the law concerning yellow lights. As everyone knows, green means go and red means stop, but what exactly does a yellow or amber light mean? Technically it is just a warning that the light will soon be turning red. However, it is against the law to accelerate through a yellow light. Police look for signs of drivers increasing their speed in order to get through yellow lights. If a driver’s speed stays constant or he/she tried to slow down but could not, they are not likely to get a ticket for going through a yellow light.

In the study, researchers found that different types of drivers and those driving different types of vehicles reacted differently to yellow lights. For instance, those who drove heavy trucks were more likely to speed up rather than slow down when they came upon a yellow light. This is probably due to the fact that it’s much harder to slow and stop these vehicles and that they are much less manoeuvrable than cars and light trucks.

They also looked at the speed of the vehicle compared to the car ahead of it when the light turned yellow. It was no surprise that if the car in front was slowing down, the driver behind would slow down as well. They felt that this was probably because the following driver didn’t want to rear-end the car in front.

They also found that those who are rolling faster when the light turned yellow tended to increase their speed and those that were traveling more slowly tended to slow down and try and stop. This too pretty much makes sense when you think about it.

One conclusion that was not as clear-cut was that more drivers would try and speed through a yellow light that lasted for five seconds than a yellow light that lasted for only three or four seconds.

Oddly enough, they also found that lane position makes a difference. Drivers who are in the right-hand lane were more likely to accelerate than those who were driving in the left-hand lane.

Statistically, about 40 per cent of drivers who are involved in deadly crashes, or those who cause serious injuries at intersections, are involved in situations where one or more of the drivers committed a traffic violation such as going through a yellow light, red light or just plain speeding.

Although the researchers didn’t come out and say it, slowing down as soon as you see a light turn yellow, is in many cases the best and safest choice.

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