What You Need to Know About Blind-Spot Detection

What is blind-spot detection?
Blind-spot detection, also known as lane-change assist, alerts drivers to cars traveling alongside in their over-the-shoulder blind spots. It supplements the coverage of your car’s rear- and side-view mirrors. Blind-spot detection is not designed to replace vigilance to what’s in your mirrors followed by a good-old fashioned glance over your shoulder before you change lanes. It is, after all, lane-change assistance.

Blind-spot detection systems use small sensors to detect traffic either side and slightly behind your car. Depending on the design of the system, the sensors employ radar, infrared, or video technology and are mounted near the outside mirrors or in the rear bumper.

How does blind-spot detection help me and my passengers?

Collisions attributed to lane changes gone wrong account for just 10 percent of traffic accidents, according to the National Highway Traffic Safety Administration (NHTSA). They’re rarely fatal, says NHTSA, but frequently result in injury and cause lots of damage.

Blind-spot detection lets you know if a car is in the adjacent lane in a position that may not be covered by your own car’s mirrors. It alerts you by illuminating small lights on your instrument panel or on the lower inside surface of your car’s front roof pillars, near the side mirrors. Some systems add an audio alert if you activate your turn signal while a vehicle is in your blind spot. To keep the focus on lane-change threats, the systems use signal-processing software to immobilize these visual or audio alerts if you’re passing another vehicle or driving next to a guard rail or median divider.

Blind-spot detection can help keep you and your passengers safe by providing early warning of a car in your blind spot. With alert lights visible peripherally or with merely a slight glance to the side, it can reduce the amount of time you’ll avert your eyes from the traffic ahead. And it can compensate for mirrors with subpar coverage or for rear-roof-pillar and rear-window designs that obscure rear visibility.

Is blind-spot detection a must-have on my car?

While blind-spot detection can be part of a collision-avoidance arsenal, it is not a must-have.

Blind-spot detection systems began to appear on cars around 2004 and today are standard equipment on top trim lines of a few expensive premium cars. Mostly, they’re found on the options lists of an increasing number of moderately priced cars, crossovers, and SUVs. Volvo offers blind-spot detection as part of a $400 option that also includes power-folding side mirrors. More typically, the system is treated as part of a broader suite of safety gizmos; Infiniti, for example, includes blind-spot detection as part of a wide-ranging $3,000 Technology Package for its luxury M-model sedans.

Good outward visibility ought to be one factor you consider when shopping for a car. Go on a test drive. If your view of surrounding traffic – to any direction – is seriously compromised, perhaps you should consider another car or another body style.

More to the point are properly adjusted side mirrors. Many drivers situate the mirrors so they include a view along the side of the car’s body. This reduces the mirrors’ ability to cover the over-the-should blind spot. To most efficiently adjust your side mirrors, sit in your normal driving position and move them outward until they in effect expand the view available in your inside mirror. The idea is to team all three mirrors to create as wide a view to the rear as possible. And nothing can take the place of a quick glance over your shoulder before you switch lanes. 

Proper use of turn signals can’t be overstated, either. Early and often is the best rule. Flipping that steering-wheel stalk gets you thinking about changing lanes before you do it, and warns other drivers of your intentions so they can alert you of their presence or take evasive action in time enough to avoid a collision.