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driving concerns

Cars sit in traffic during rush hour in Bucharest, Romania.Lucian Alecu/iStockPhoto / Getty Images

What is the recommended distance between cars when you’re stopping at a red light? – Teresa

When you’re stopped behind another car at a light, so far is so good.

“I usually leave two car lengths between my car and the vehicle in front of me,” said Ian Law, president and chief instructor of ILR Car Control School in Brampton, Ont.

A gap of one or two car lengths gives you a buffer in case the car behind you doesn’t stop.

With all that space, you might be able to steer out of the way If you see another car sliding toward you in your rearview mirror, Law said.

“That gap saved me a few times,” Law said.

One time, a drunk driver came up behind him, hit the brakes but didn’t stop in time, Law said.

“I started to move forward before he rammed my car,” Law said. “The extra room allowed me to pull ahead and minimize the damage.”

If you do get rear-ended at a stop light, that gap makes it less likely that you’ll be pushed into the vehicle in front of you.

That gap is also handy if the car in front of you suddenly stalls.

“One car length is the minimum amount of space for you to be able to navigate around the vehicle in front,” said Angelo DiCicco, special project manager with the Ontario Safety League. “If you got much closer than that, you’d have to reverse.”

Space invaders?

All provincial traffic laws say you have to stop at a light, but none of them specify a distance you have to keep from the car in front.

In the seventies and eighties, driving instructors told students to stop so they could just see the tires of the car stopped in front of you.

These days, that old-school advice cuts it too close, Law said.

“Back then, the hoods of most cars were a mile long,” Law said, “Now you can literally be almost on top of the car in front and still see the rear tires.”

But f you leave that big gap on a street with multiple lanes, won’t another car just pull into it?

“In the 25 years I have been doing this, I can count on one hand the number of times that has happened,” Law said. “And when it does happen, so what? Another car in front of me might add 20 seconds to my travel time.”

Some drivers pull close to the cars in front of them at stop lights because they think they’ll be able to get through the light faster when it turns green.

But a 2017 Virginia Tech study found that cars took about the same amount of time to get through a light whether they had stopped anywhere from 30 centimetres to 8 metres from the car in front of them.

That’s because once the light turned green, cars had to wait for the cars in front of them to get a safe distance away before moving.

“You can just maintain whatever spacing you had when you were driving at full speed,” Jonathan Boreyko, a Virginia Tech assistant professor who co-authored the study, told Science Daily. “You won’t lose any time, but you’ll reduce the odds of an accidental rear-end collision.”

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