Checking your blind spot with a quick glance over your shoulder is routine – and one of the first things people are taught when learning to drive. A shoulder check provides visual confirmation that no cars or pedestrians are on either side of your car before turning or making a lane change. But there’s also a way to adjust the outside side mirrors to eliminate these blind spots. (Although a shoulder check is still recommended).
In 1995 the Society of Automotive Engineers (SAE International) published a paper titled, “The geometry of automotive rear-view mirrors – why blind zones exist and strategies to overcome them.” It suggests another way to set up your mirrors to eliminate blind zones.
After using this mirror position for so many years, I swear by it. There have been a few instances when the shoulder check has taken my attention away long enough that the car in front has stopped abruptly, and I’ve had to slam on my brakes to avoid running into it. Looking in the side mirrors to check your blind spot takes your eyes off the road for a shorter time and I feel it’s made me a safer driver.
You can buy “blind-spot” mirrors to stick to the corners of your side mirrors that effectively do the same thing, but the image is usually small and hard to see. In other parts of the world, convex or aspherical mirrors (curved mirrors with a wider field of view than flat mirrors) can be installed on the driver’s side, but our federal regulations, which are similar to those in the United States, don’t allow them to be used as the main side mirror. The law doesn’t apply to secondary mirrors that you can attach to it.
In Canada, the minimum requirement is to have one rear-view mirror inside the car and one exterior mirror on the driver’s side. Passenger mirrors aren’t required but all new cars have them. The driver side mirror must be a flat unit magnification mirror and the image has to be 1:1, or life-size. The passenger side mirror can be convex but needs to come with a warning that states, “The objects in this mirror are closer than they appear.”
When it comes to adjusting mirrors, Brian Hart, a training manager at Young Drivers of Canada, has seen other drivers who set too high or too low and some that are too far inward, only showing the side of the car and little else. He says all the students that attend Young Drivers are shown the standard method of side mirror adjustment.
“You want a nice, even horizon through the middle of the mirror and, when you turn your head to look at the mirror, you want to see a slight sliver of the rear of the car,” Hart says. “We try to set it up with the students in the vehicle and we adjust as much as we can to minimize the blind spots, but we’re not trying to eliminate them.”
Adjusting the mirrors this way involves angling them more inward so you can see cars in the next lane directly behind your car. But for years, I’ve angled them more outward to provide a view of the lanes to the right and left of the rear part of my car, effectively eliminating these blind spots. Because they’re angled quite far outward with this method, the side mirrors no longer show what’s directly behind, which can be disorienting for those who aren’t used to it. The idea here is that the interior rear-view mirror already shows what’s behind you and you don’t need two additional mirrors to replicate what it’s already doing.
To adjust your mirrors to show blind spots, sit in the driver’s seat in a parked car and lean your head against the side window. Move the driver mirror outward until only a small portion of the side of the car is visible. For the passenger side adjustment, lean over to the other side so that your head is above the centre console and adjust the mirror so that, like the driver-side mirror, only a bit of the car can be seen. When you return to your normal position, you shouldn’t see the car’s flanks in the mirrors.
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You can fine-tune it after driving a bit, but if you’ve done it correctly, all three mirrors work together. Vehicles coming up from behind in the adjacent lanes will move from the rear-view mirror seamlessly into the side mirror as they begin to enter your blind spot and pass you. Instead of cranking your head to look over your shoulder, just quickly glance at the side mirror to check your blind spot. You don’t even have to move your head.
While he’s familiar with this method and agrees on its merits, Hart says it doesn’t work if your rear view is obstructed.
“With your mirrors that far out, you won’t see what’s behind you and that’s the main reason we teach the conventional way,” he says. “There are cars where [adjusting the mirrors that far out] isn’t possible. And there are panel vans and trucks that don’t have a rear window or rear-view mirror, so the blind spot adjustment won’t work for those.”
Many new cars have blind-spot monitors; some can even steer you back into your lane if they detect an imminent collision. I’ve been in Ubers where the driver relies on the audible blind spot warning instead of performing a shoulder check.
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While that technology is helpful, Hart says it doesn’t replace our driving skills because it can fail. “We get students out in the parking lot and get instructors to stand in their blind spots so they get an understanding of why checking it is important,” says Hart.
There’s also the all-important driving test. Preparing students for success is one of the main things a driving school does. “Adjusting the mirror out that far would not eliminate the ministry’s requirement to [physically] check your blind spot,” Hart says. “A shoulder check is still [a ministry requirement] of the road test.”