Guide to Blind Spot Warning

How this technology improves safety by monitoring a vehicle's flanks

Illustration of a car's side mirror with a warning indicator Illustration: John Ritter

“Once I got used to the blind spot warning and how it activates, it became a natural [part of] my driving routine,” the owner of a 2017 Chevrolet Bolt wrote in response to a recent Consumer Reports member survey. Those words echoed what we heard from many members, who told us that blind spot warning (BSW) has kept them from crashes and made driving less stressful.

BSW systems use cameras, radar, and/or ultrasonic sensors alongside your vehicle to detect vehicles you can’t see that are in your blind spot—or quickly approaching it from behind your car. If a vehicle is detected, drivers usually get a visual warning, commonly in the side mirrors, or on the front pillars next to the driver’s window. When drivers activate the turn signal, some BSW systems give an audible and/or tactile alert (shaking the steering wheel, for example) to indicate that it’s unsafe to merge or change lanes. 

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Some newer vehicles may even have a Blind Spot Assist function, which may slightly correct the steering wheel or even apply the brakes to avoid a potential collision when the turn signal is activated and there’s an obstacle in the blind spot.

In prior surveys, two-thirds of drivers who used BSW told us it helped to prevent a crash. Now a commonplace option on many affordable vehicles, some survey respondents told us they wouldn’t buy a vehicle without it. “It is a practical and useful feature that I now consider a critical requirement in any future auto purchase,” wrote the owner of a 2020 Subaru Forester.

BSW systems come in two varieties:

Blind Spot Warning (BSW): This detects vehicles in the blind spot while driving and notifies the driver to their presence. Some systems provide an additional warning if the driver activates the turn signal when it is unsafe to merge or change lanes.

Blind Spot Assist (BSA): The BSA system automatically steers and/or brakes when the turn signal is activated during a lane change maneuver and a vehicle is occupying the blind spot in an adjacent lane.

In our most recent car safety survey, we asked CR members to rate their experiences with the advanced safety and driver assistance systems on their model-year 2017 to 2022 cars. Respondents answered questions about their satisfaction with the systems and told us which ones helped them avoid a crash. The survey covered about 47,000 vehicles. Satisfaction was higher for newer vehicles, indicating that these systems may be improving as time goes on.

Many drivers highlighted how important BSW is in modern vehicles, which tend to have larger side and rear blind spots.

“The blind spot warning light is helpful because there is a large pillar behind the rear passenger seat that blocks being able to see the blind spot if I turn my head,” wrote the owner of a 2019 Honda CR-V. The driver of a 2018 Cadillac XT5 agreed. “This car has a big blind spot so this feature is very useful,” they wrote.

Blind Spot Warning (BSW)

OVERALL SATISFACTION

64%

What to Look for in a Blind Spot Warning System?

The best BSW systems put warning lights in a vehicle’s side mirrors, says Kelly Funkhouser, manager for vehicle technology at CR. “You should already be checking your mirrors, so it’s the natural place to put a warning,” she says. “Warning lights or camera views on the dashboard or elsewhere can be distracting and take a driver’s eyes away from the location they should be looking.”

She also recommends systems that allow drivers to customize the sensitivity and type of warning. Some of our survey respondents said they prefer a system that gives only a visual warning, saving a louder audio warning for those times where a driver is about to actively hit a vehicle. Systems that frequently sound loud alarms can be distracting, Funkhouser says. 

Before you buy a car, she recommends that you look in the owner’s manual to learn more about the BSW system. These can often be accessed online through the automaker’s website, in the “owner’s” section.

CR’s take: BSW is one of CR’s recommended safety features. CR gives bonus points to models that have it as standard equipment across all trims, and our members also rate it favorably. It makes for safer lane changes, and it is a real boon for drivers in vehicles with big blind spots. CR’s testers prefer systems that use a bright warning light on the side mirror, as opposed to on the infotainment display screen or instrument cluster. Even if shoppers have to pay extra for this feature, we don’t think they’ll regret it. 

Brand Names for Blind Spot Warning

CR, AAA, J.D. Power, and the National Safety Council have agreed on standardized, specific names for about 20 key individual safety systems in order to reduce confusion and improve consumer understanding of what they do. Still, manufacturers often use their own names for these systems. These are some of the names that automakers use or have used for blind spot warning:

Acura: Blind spot information
Alfa Romeo: Blind spot detection
Audi: Audi side assist
BMW: Blind spot detection, Active blind spot detection
Buick: Side blind zone alert
Cadillac: Side blind zone alert
Chevrolet: Side blind zone alert
Chrysler: Blind spot monitoring
Fiat: Blind spot monitoring
Ford: Blind spot information system (BLIS)
Genesis: Blind spot detection
GMC: Side blind zone alert
Honda: Blind spot information, Blind spot monitoring
Hyundai: Blind spot collision warning, Blind-Spot Collision Avoidance Assist
Infiniti: Blind spot warning
Jeep: Blind spot monitoring
Kia: Blind spot collision warning (BCW)
Lexus: Blind spot monitor
Lincoln: Blind spot information system
Mazda: Blind spot monitoring, Rear vehicle monitoring system, Advanced blind spot monitoring
Mercedes-Benz: Blind spot assist, Active blind spot assist
Mini: Blind spot detection system
Mitsubishi: Blind spot warning
Nissan: Blind spot warning
Porsche: Lane change assist
Subaru: Blind spot detection
Toyota: Blind spot monitor
Volkswagen: Blind spot monitor
Volvo: Blind spot information


Head shot photo of CRO Cars CIA editor Keith Barry

Keith Barry

Despite my love for quirky, old European sedans like the Renault Medallion, it's my passion to help others find a safe, reliable car that still puts a smile on their face—even if they're stuck in traffic. When I'm not behind the wheel or the keyboard, you can find me exploring a new city on foot or planning my next trip.