Vehicles drive on a road with the Gordie Howe International Bridge in the distance, in Windsor, Ont., on Feb. 4.Carlos Osorio/Reuters
I see that there’s no exact distance that you have to stop from another car at a red light, but what about when driving? Does the law specify how far you have to be from the car in front of you? If not, how do police decide when to charge somebody with tailgating? – Henri, Toronto
The law doesn’t say how far you need to be from the car in front of you – it just says to be “reasonable.”
But that’s more space than most of us think, safety experts said.
Section 158 of Ontario’s Highway Traffic Act states you must not follow another vehicle “more closely than is reasonable and prudent having due regard for the speed of the vehicle and the traffic on and the conditions of the highway.”
Sean Shapiro, a traffic safety consultant and former Toronto police officer, said the wording of the law is “loosey-goosey” and it’s up to officers to decide whether you’re following too close – which comes with a $110 fine and four demerits.
“It doesn’t tell you how close you can be,” Shapiro said. “We used to say ‘if grandma thinks it’s a good idea, it’s probably a good idea’ – but if your grandma likes fast cars, she might not be the right person to ask.”
The laws in most other provinces, including British Columbia, Alberta and Quebec, are similar.
While some, including Ontario and B.C., require specific following distances for commercial vehicles, they don’t for everyone else.
“One of the best indicators of following too closely is when a driver causes a rear-end collision,” Corporal Michael McLaughlin, spokesman for B.C. Highway Patrol, said in an email.
Three-second rule?
So, how close is too close?
Generally, provincial driving manuals describe following distances in seconds instead of metres or car lengths.
For instance, in B.C., Alberta and Ontario, manuals say to keep at least a two-second distance in good weather.
“You find a fixed object, like a light pole and you start counting: one one thousand, two one thousand,” Shapiro said.
Measuring in seconds works because it’s tough for most of us to estimate distances while driving, he said. Plus, the safe following distance in metres or car lengths increases the faster you go. You need to keep more room at 100 kilometres an hour than you do at 50 kilometres an hour.
Shapiro suggests up to three seconds in city traffic in good weather and at least four seconds on slippery or icy roads.
“If traffic isn’t moving at all, then leave a car length,” he said.
But at highway speeds, he said you should be at least four seconds from the car in front of you in ideal conditions. If the weather is lousy or you’re following a big truck or motorhome, the gap should be five to six seconds.
You need that time to register what the car in front of you is doing and then to react, he said.
“You’re travelling a tremendous distance as you decide what to do and put that plan in action,” Shapiro said. “If you’re following too closely, you’ve already hit the car in front of you.”
If your car has adaptive cruise control – which automatically keeps a specific distance from the car in front of you – you should use it, said Angelo DiCicco, general manager of the Ontario Safety League, a Mississauga-based nonprofit focusing on driver education.
But if you keep too much space, won’t another car just pull in front of you?
“They might. So you have to readjust every time somebody takes up your space,” Shapiro said. “Guess what? That’s what we call driving.”
Have a driving question? Send it to globedrive@globeandmail.com and put ‘Driving Concerns’ in your subject line. Emails without the correct subject line may not be answered. Canada’s a big place, so let us know where you are so we can find the answer for your city and province.