When two cars are trying to move into the same lane on a highway, who has the right of way?

When changing lanes on a multilane road such as Highway 401, does any lane have right of way over other lanes? If there are three lanes and the car from the left lane and a car from the right lane are trying to move into the middle lane at the same time, which car has the right of way? Does the faster left lane have priority over the slower right lane? Or vice versa? – Jonathan, Toronto

When two cars are trying to get into the same lane, nobody gets dibs.

“Neither has an automatic right of way to that lane,” said Sean Shapiro, a road safety consultant and former Toronto traffic cop. “Both drivers have an obligation to make sure their lane change can be completed safely before they move.”

There’s no general rule in Ontario giving a driver in a particular lane the right of way when changing lanes.

Ontario’s law states that “a vehicle shall not be driven from one lane to another lane … unless the driver first ascertains that it can be done safely.”

While the rules vary by province, they’re similar across Canada: you have to make sure it’s safe before switching lanes.

British Columbia’s law goes a step further. It states that you can’t change lanes unless “the movement can be made with safety and will in no way affect the travel of another vehicle.”

Also, you generally need to signal before making your move.

The lane truth?

So how do you make sure it’s safe – especially if you’re trying to get into a middle lane?

“Don’t just check the lane immediately beside you,” Angelo DiCicco, chief executive officer of the Ontario Safety League, a nonprofit that focuses on driver education, said in an email. “You also need to be aware of what is happening two lanes over because another driver may be trying to enter the same space at exactly the same time.”

That means checking your mirrors – and making sure they’re properly adjusted in the first place – and doing a shoulder check.

Aside from watching out for drivers farther back in the next lane who might be speeding, you’re looking for cars two lanes over that might be signalling a move into that lane – or already making it, DiCicco said.

“The objective isn’t simply to see where the other vehicles are,” he said. “It’s to anticipate where they may be going.”

And, if there’s a car driving parallel to you in that far lane, it might be a good idea to wait until they’re clear – just in case they decide to get into that centre lane and don’t see you moving or signalling.

“Two drivers can both make what appears to be a perfectly normal lane change and still end up competing for exactly the same piece of pavement,” DiCicco said.

Crossed signals?

When you signal to move over, it doesn’t mean the lane is yours, Shapiro said.

“A turn signal communicates your intention,” he said. “It doesn’t reserve the lane for you, and it doesn’t give you the right of way.”

And other drivers might not even be paying attention to your signal.

“Never assume another driver has seen your signal, seen your vehicle or understood what you intend to do,” DiCicco said.

So what if, despite all the precautions, two drivers both still try to get into the same lane at the same time?

“They both have an obligation to react and avoid the collision,” Shapiro said.

If one car gets there first, the other car has to abandon the move, he said.

“The other driver is now attempting to enter an occupied lane and must make sure that movement can be made safely,” Shapiro said.

Who would be at fault if you both move into that lane at the same time and cause a crash?

Most provinces have rules to determine who’s at fault in many common collision scenarios.

For instance, in Ontario, those rules say if you change lanes and hit a car that’s already there, you’re entirely at fault.

But if you’re both changing lanes when you hit each other, fault is generally split 50/50 – no matter who started moving first, Rob de Pruis, the national director of consumer and industry relations at the Insurance Bureau of Canada, said in an email.

If you were already fully in the lane when the other driver hit you, you would likely need video evidence – for instance, from a dash cam – or witnesses to prove it, de Pruis said.

The rules in other provinces are similar, he said.

Rules only go so far

Even if there were clear rules for right of way when switching lanes, they wouldn’t magically prevent a crash, DiCicco said.

Some drivers might not know them or they might just ignore them. And, even when there are clear rules for right of way in other situations on the road, you always have to make sure it’s safe before making a move.

“We naturally want a clean rule or formula that tells us who has the right of way,” he said. “But the bigger question is ‘Does that other driver see me, and what are they about to do?’”

Have a driving question? Send it to globedrive@globeandmail.com and put ‘Driving Concerns’ in your subject line. E-mails 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.