What Does BSM Mean on a Car? How Does It Work?

Tim Miller

Seeing the BSM button or light on your car and you’re wondering:

  • What does the BSM mean?
  • How to use this feature?
  • How does it work?

I’ve created this guide to answer your questions, from how BSM works to how to use it.

Read on to learn more.

What Does BSM Light Mean?

BSM light
The BSM system is designed to help you avoid collisions by alerting you to the presence of other vehicles that may be out of your line of sight.

BSM, short for blind spot monitoring, is a term for a camera system that helps you detect and monitor vehicles or other objects that may be in your blind spots. It covers the areas alongside or behind your car.

Depending on your car’s model and brand, the BSM system will alert you when a car or object is detected in your blind spot via a small beep or warning light on your rearview mirror.

Manufacturers give their BSM different names, such as Active Blind Spot Assist (Mercedes-Benz), Blind Spot Information System (Volvo), and Side Blind Zone Alert (GM).

Overall, the BSM is designed to help you avoid collisions and improve safety while driving.

How to Use BSM

How to use BSM
When a vehicle is detected in your blind spot, the warning light will illuminate.

The BSM activates in some vehicles when you drive over a specific speed. Once the system is functional, the BSM light will come on in the window frames and rearview mirrors. The BSM symbol looks like a car pointing a beam at another vehicle.

Some car models need you to activate the feature after starting the car. You have to press the BSM button to turn on the system.

How Does the BSM Work?

The BSM system uses cameras or sensors to detect objects, like cars, that may be in your blind spot when driving. Manufacturers often place these sensors under the side-view mirrors or rear bumpers.

The sensors track the areas next to and behind the vehicle. It covers about one lane width on the left and right sides of the car. BSM identifies items entering your blind spot from the front, back, and side.

How BSM works
If the BSM system detects an object in the blind spot, it typically sends a signal or alert to you.

Once the system identifies an approaching vehicle, a yellow light will illuminate the window frame or side mirror from where it is coming. Some cars will also alert you with a sound to ensure you’re aware of the vehicle in the areas you cannot see.

The sound and warning lights are to alert you of what is happening around your car so that you can take appropriate action to avoid an accident.

Some advanced systems will vibrate your steering wheel and activate the indicator light if an object is detected in a spot that is outside of your line of sight while your turn signal is on.

Note that your BSM system is not designed to let you know of small objects like bicycles and motorcycles. If a small item is in a blind spot, the BSM sensors might not detect it, preventing the warning light from lighting up.

The Blind Spot Monitoring system also works with other systems in a car, like the Lane Keeping Assist, Lane Departure Warning, and Rear Cross Traffic Alert, to provide a complete suite of safety features to protect you, your passengers, and the car.

I had an experience with this system a few months ago while driving on a dual-lane road. My Toyota RAV4 alerted me of a vehicle trying to overtake me because I was driving in the middle of the lane.

I adjusted to my lane, and the indicator turned off immediately after the car passed.

This system serves as your eyes around your car. In addition to keeping you safe, it helps prevent unprecedented collisions that could damage your vehicle. 

What’s Next?

The Blind Spot Monitoring system is an important safety feature designed to inform approaching vehicles. The system will show where the car is coming from, whether back, front, or sides.

But remember that this feature is not a replacement for safe driving practices. Always drive carefully and check your blind spots before merging into traffic or switching lanes.

Now it’s your turn.

Has the BSM system ever helped you while driving? Please share your experience with me in the comment box below.

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Information sourced from the owner's manual.