Traffic Light Dilemma: How Close Should You Get to the Car in Front of You?

Nov 30, 2017

Credit Kenny Louie / Flickr

Right now, you might be sitting at a stop light, inching forward to make it through the intersection on the next green signal. Researchers at Virginia Tech recently did some work that might get you through faster.

While sitting behind a line of cars at a red light one day, Virginia Tech assistant professor Jonathan Boyreko pondered a simple question:

“And I noticed when the light turned green I had to wait for I think over an entire minute before I could finally start to move and it just made me think about is it actually smart what we currently do to – getting as close as possible to the car in front of you at a red light, or is that not worth the effort because you have this lag effect to get the spacing back before you can move anyway.”

From there Boyreko and a team of researchers set out to find the answer to that question.

The research group gathered volunteers to systematically check whether the distance between cars at a stop light has anything to do with how fast one can get through an intersection following a green light.  Ph. D. student Farzad Ahmadi is the study’s lead author.  

“And we had a drone that we attached a camera to that and we could be able to actually capture the motion of the vehicles that when they were just actually trying to pass the intersection.”

Volunteers approach a traffic light on the Virginia Tech Transportation Institute's Smart Road. The research team found that the space between cars at a red light does not impact how long it takes to get through the intersection.
Credit Virginia Tech

Boyreko says that effort took around 6 months to put together which ultimately led to an answer:  

“We just kind of found the time doesn’t change no matter what. No matter how close or far apart you are, all the cars get through in the same time regardless.”

And while there are some exceptions, like major metropolitan areas, the team found that keeping your distance actually reduced the risk of minor traffic incidents.

This report, provided by Virginia Public Radio, was made possible with support from the Virginia Education Association.