Understanding Blind Spots and How to Check Them

What a blind spot is

A blind spot is any area around your vehicle that you cannot see directly, or in your mirrors, from the normal driving position. Every vehicle has them. They can hide another car, a motorcycle, a cyclist or a pedestrian, and the problem is that you may not know anything is there until you begin to move.

The most familiar blind spot is on either side of the car, just behind the driver and passenger doors, where a vehicle can sit in the gap between what your side mirror shows and what you see through your side window. But there are others.

Where blind spots occur

• Beside and slightly behind the car. This is the classic “over the shoulder” zone, and the reason for the shoulder check.
• Behind pillars. The frames that hold up the roof, particularly the front pillars either side of the windshield and the rear pillars, can hide a pedestrian, a cyclist or another vehicle, especially at junctions and when turning. Moving your head slightly can reveal what the pillar hides.
• Directly behind the car. Low objects, small children and pets may not be visible through the rear window or in the mirror, particularly close to the bumper. Trucks, SUVs and vans with high rear ends tend to have larger areas here.
• Directly in front of tall vehicles. A high hood can hide things close to the front.
• Behind other vehicles. A large truck or van ahead can hide traffic lights, signs and slowing vehicles. This is another reason to keep a larger gap, as in following distance.
• Rain, fog, snow and darkness. Poor visibility effectively enlarges blind areas, since objects are harder to pick out. See night driving and fog driving.

Larger vehicles such as trucks and buses have bigger blind zones on all sides. A common recommendation is that if you cannot see the driver’s mirrors, the driver may not see you, so avoid lingering beside a truck and pass it without delay.

Why mirrors and cameras do not remove them

Mirrors show only a limited angle. Convex side mirrors, which are curved to widen the view, make objects appear smaller and farther than they are, and they can distort speed. A properly aimed mirror reduces blind spots, as covered in mirror adjustment, but cannot remove them entirely.

Many newer cars have blind-spot monitoring that lights a warning in the mirror when a vehicle is detected, as well as rear-view cameras and sensors. These are real aids and are part of the wider range of safety features. They have limits, though:

• Sensors can miss fast-approaching vehicles, motorcycles, bicycles and pedestrians.
• Dirt, snow or ice may block the sensors or the camera.
• Cameras show a limited field of view and can distort distances.
• A system that is not working may give no warning, so you can be misled into over-trusting it.

The safest approach is to treat these as a backup, not a substitute for your own checks. Check your owner’s manual to learn what your car’s systems do.

How to check a blind spot

The shoulder check

The shoulder check is a quick look over your shoulder, toward the area you cannot see in the mirrors.

1. Check your interior and side mirrors first, as covered in the routine in lane changes.
2. Signal your intention.
3. Turn your head, and look briefly over the relevant shoulder. Look through the side window, not the rear window. For a move to the left, look over your left shoulder, and for a move to the right, over your right shoulder.
4. Return your eyes to the road ahead right away. A glance of about a second is typically enough.
5. If the space is clear, make the move smoothly. If something is there, wait and repeat.

Keep your hands steady on the wheel while you turn your head so the car does not drift. If you have trouble turning your head because of stiffness or a medical condition, discuss adaptations with a qualified professional, since mirrors and aids may need to be adjusted.

Move your head to see around pillars

At junctions and crossings, lean forward or sideways slightly so that pillars and mirrors do not hide what is approaching. A cyclist or pedestrian can be fully hidden behind a pillar for a surprising time.

Check behind before reversing

Before backing up, walk around the car if there is any doubt, especially with children nearby. Then:

• Look in all directions, including over your shoulder, and use your mirrors.
• Use your backup camera and sensors as an extra aid, not the only one.
• Reverse slowly, ready to stop immediately.

For tips on reversing into a space, see parallel parking.

Habits that help

• Make the shoulder check automatic. Do it every time before pulling away from the curb, changing lanes, merging or turning, even if the mirror looks clear.
• Avoid sitting in other drivers’ blind spots. Adjust your speed so you are not alongside a vehicle for long. Either pass completely or drop back. Simple speed changes, like the ones in defensive driving, reduce risk for both of you.
• Keep windows and mirrors clean. Dirt and fogged glass shrink what you can see. Use the methods described under defrosting windows.
• Remove obstructions. Items hanging from the mirror, stickers or stacked cargo can create extra blind spots.
• Be aware of motorcycles and bikes. Their narrow shape makes them easier to miss.
• Consider extras with care. Small stick-on convex mirrors can widen the view, but they may also distort. Try them in a safe setting before relying on them.

Pedestrians and parking lots

Parking lots are full of blind areas: pillars, vans, carts and people stepping out. Drive slowly, scan between parked cars, and be ready to stop. When leaving a space, reverse gradually and watch for vehicles approaching from either side.

A last point

No habit makes you invulnerable. Other road users can also move into your blind spot at the worst moment, and you may sometimes misjudge a gap. What checking does is reduce the odds. Make each check quick and consistent, and if something feels uncertain, wait. Rules and recommended practice differ by region, so see your local driver’s handbook if you want specifics.