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Is it always the case that the best place to install a convex blind-spot mirror is the upper left for the left side mirror? – Robert

There’s no clear view on the best spot for blind-spot mirrors. If your mirrors are adjusted properly, you might not need them at all, safety experts say.

“The existing mirrors on most vehicles should be able to cut down on the majority of blind spots,” said Lewis Smith, manager of national projects with the Canada Safety Council (CSC), in an e-mail.

How do you know if your side-view mirrors are adjusted properly? When you look in them while you’re driving, you shouldn’t be able to see the sides of your car. You don’t need to see the sides of your car because the mirrors are there to show you the lanes on either side of you, and not whether you left the gas cap open.

The best way to adjust them? First, park the car. Then lean your head against the left window and adjust the left mirror so you just barely see the left side of your car.

Next, lean to the right, to about the middle of your dash, and adjust the right mirror just until you can just barely see the right side.

If it's done properly, a car passing to your left or right should start to appear in your side view mirror just as it starts to move out of your rear-view mirror.

The idea isn’t new. A 1995 technical paper called this the Blind Zone and Glare Elimination (BGE) setting.

"When driving with the BGE Setting, most drivers initially feel a sense of confusion with the outside mirrors; you are not sure where they are pointed; you miss not seeing the sides of the car and you do not know how to interpret what you see," Platzer wrote. "Don't give up. The confusion will go away."

Sticky problem?

If you’ve adjusted your mirrors and still think a stick-on convex blind-spot mirror could help, what’s the best spot? It’s up to you, according to K Source, a California-based company that makes them.

The best place for a mirror “varies from person to person,” said Adrian Diaz, who works on research and development for the company, in an e-mail.

Generally, blind-spot mirrors should be in an outside corner of the mirror so you can see the blind spot but still keep the rest of the mirror clear so you can see traffic beside your car, says CSC’s Smith.

“There are conflicting schools as to whether [blind-spot mirrors] should be placed in the upper outside corner or the lower outside corner,” Smith says. “Because different car makes and models have different blind spots, there’s no one-size-fits-all solution.”

Even if your mirrors give you a clear view of blind spots, you’ll need a reality check – you should always be shoulder checking before you switch lanes or turn right.

“Think of the smallest things that can disappear into a blind spot, like a cyclist or a child,” Kristine D’Arbelles, spokeswoman for the Canadian Automobile Association (CAA), said in an e-mail.

That advice applies even if your car has blind-spot detection, according to driving instructor Ian Law.

“Yes, checking your blind spot is always important,” said Law, who is the president and chief instructor of ILR Car Control School, in an e-mail. “Those silly ‘blind-spot assist’ gadgets will not pick up a vehicle changing lanes from the second lane over.”

Have a driving question? Send it to globedrive@globeandmail.com. Canada’s a big place, so let us know where you are so we can find the answer for your city and province.

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