Blind Spot Monitoring

By SRT-Tom · May 19, 2022 ·
  1. SRT-Tom
    What is Blind-Spot Monitoring?

    Blind-spot monitoring one of those features we didn’t know we needed or wanted until carmakers began offering it. Volvo was the first, incidentally. It offered its Blind Spot Information System (BLIS) for the S80 in 2005.

    BSM is just what its name implies. It keeps an eye on the space just off the rear quarter areas of your vehicle. These blind spots can hide a vehicle approaching in an adjacent lane because many drivers improperly set their car’s outboard mirrors. Consequently, merging into that lane often results in a crash.


    As far as today’s crop of driver-aid technologies goes, blind-spot monitoring is quite simple. The least sophisticated examples use radar or ultrasonic sensors embedded in each side of the vehicle’s rear bumper. These sensors detect a vehicle approaching the rear of your car in an adjoining lane. More sophisticated BSM systems also employ side-mounted cameras.

    Blind-spot monitoring is one of the most useful tools for keeping safe. If you pay attention to the audible or visual warnings, they can minimize your changes of merging into another vehicle. Systems with collision prevention functionality add further value to blind-spot monitoring because they actively steer or brake, adding another layer of security during your drive.

    When BSM recognizes a vehicle about to enter a blind spot, it warns you that a particular adjoining lane is not clear. Commonly, the alert comes in the form of a yellow warning light somewhere on the outboard rearview mirror on whichever side of the oncoming car is involved. It may, instead, appear on your vehicle’s A-pillar (the pillar between the windshield and either front door), driver-information display, or head-up display.

    A few brands, such as Honda and Kia, provide an audible alert in some models. Often, audible alerts will sound if you use your turn signal, indicating you will merge into an occupied lane.

    How Does It Work?

    Blind-spot monitoring uses a combination of sensors and sometimes side-mounted cameras to track approaching traffic in adjoining lanes. You can often spot the sensors. They are usually quarter-size round indentations in the bodywork or fascias and are

    mounted on the side mirrors or rear bumper to detect vehicles in the adjacent lanes. If the sensors detect something, they'll alert you via an audible and/or visual warning. Some vehicles even use a camera as the main part of the system or to complement the sensors.


    Once BSM senses an advancing vehicle, it springs into warning mode. Some blind-spot monitoring systems are so sophisticated that they will nudge you away from the lane marker on that side. The system may even steer you back to the center of the lane.

    As the cost of the tech has gone down, the safety and convenience feature is now offered across the market—not just on luxury vehicles. Models ranging from the subcompact Nissan Versa to massive trucks like the Ford Super Duty all offer the feature. You'll often find blind-spot monitoring bundled with a rear cross-traffic alert feature, which detects vehicles, objects, or a pedestrian in the car's way when reversing out of parking spots.

    Types of Blind-Spot Monitoring Systems

    Currently, there are basically two types of blind-spot monitoring systems. The less-intrusive system simply provides an alert. The more intrusive system pairs the alert with steering assistance.

    Blind-Spot Warning

    Just an alert, this BSM system issues a visual warning usually found on the outboard mirror or the A-pillar on the side with the potential danger. More involved versions will also sound an audible warning if you engage the turn signal on that side.

    Blind-Spot Warning with Automatic Emergency Steering

    Automakers have recently expanded beyond detecting what's in your blind spots. A recent upgrade to blind-spot monitoring is a change from passively warning to actively helping the driver avoid a potential collision. For example, if the car you're driving detects a car next to you when you're about to change lanes, it can manipulate the steering and brakes to try to avoid a collision.

    Advanced Blind-Spot Monitoring Systems

    As technology tends to do, blind-spot monitoring continues to evolve. When first introduced, fewer than 20 years ago, BSM was a novelty reserved for premium and luxury cars. Today we find it on the most affordable of models. For example, it’s standard on the $19,500Nissan Kicks S and comes with the $500 Technology Package for the $19,590 Kia Forte LXS.

    As already mentioned, cutting-edge BSM versions that either nudge you away from the lane marker or steer you back to the lane’s center are also available in many cars. They accomplish this through steering or by applying brake pressure to one or more wheels.

    Even full-size pickup trucks are getting into the act. No matter the brand, every full-size pickup has blind-spot monitoring either standard or available. The Ford F-150 and Ram 1500pickup trucks take it even farther. They offer BSM that extends to the trailers they are towing.

    Blind-spot monitoring often pairs with rear cross-traffic alert (RCTA), which uses the same sensing tools as BSM. Whether it’s backing into other vehicles or backing into people, a lot of mayhem occurs when backing up in parking lots. RCTA comes to life when you shift into reverse. Less sophisticated systems monitor vehicles on a course to cross behind your car. When rear cross-traffic alert detects a crossing vehicle, it issues an audible warning.

    More advanced RCTA systems also recognize pedestrians and sound an alert when a pedestrian is behind you. Even more advanced systems will sound an alert and automatically apply the brakes.

    What To Look for in A Good BSM System?

    1. Find the location of the indicator lights. They're usually on the side mirrors outside the cabin or inside the car, on the A-pillar next to the window.
    2. Check if you can change the warning chime's volume. Some blind-spot monitoring systems may emit loud sounds in their default setting.
    3. Find out if the system includes rear cross-traffic alert or rear cross-traffic braking. Both can provide added peace of mind in busy parking lots when you're reversing and have limited visibility.



    According to the National Highway Traffic Safety Administration (NHTSA), with nearly 10% of vehicle accidents being lane-changing crashes, BSM can be a useful tool when utilized. In a 2017 article, the Insurance Institute for Highway Safety (IIHS) reported that blind-spot monitoring reduces lane-changing accidents by 14%. Moreover, it reduces injuries from lane-changing crashes by 23%.

    BSM is an active driver aid/safety device with the ability to detect what your eyes may miss, issuing a warning as a vehicle approaches in an adjoining lane.

    Once only found in high-end luxury cars, blind-spot monitoring eventually trickled down to even economy cars. If BSM isn’t standard on a vehicle, it’s probably available as a stand-alone option or in an option package. The larger your vehicle, the bigger the blind spot. The bigger the blind spot, the more BSM can help prevent you from changing lanes into another vehicle.

    Tips for Using Blind-Spot Monitoring

    To maximize the effectiveness of blind-spot monitoring, it is recommended that you:

    1. Wipe off the cameras: Ensure the cameras and sensors are free of dust, mud, snow, and whatever else might interfere with their proper functioning. Clean them off and wipe them down.

    2. Check your car manual for setup: Consult your owner’s manual for specifics on engaging and setting your active driver aids. That way, you can stay safe while driving.

    3. Know the system’s limitations: Be aware of any limitations your particular system may have. Not every BSM system operates the same. Some may only function at certain speeds and so forth. Every blind-spot monitoring system doesn’t recognize pedestrians, cyclists, and pets.

    4. Use your eyes: Before traveling in reverse, always double-check with your own eyes what is behind you.

    What BSM Does Not Do

    Here is an excerpt from a Dodge Challenger Owner’s Manual describing what a BSM system does not do.




    If your vehicle has blind-spot monitoring, it most likely came from the factory that way. Built-in BSM is the more common system because it makes sense. The sensors are nearly seamless in a factory system and are exactly where they need to be for the most effective performance. The warranty covers the system and so does your auto insurance.

    Blind Spot Monitoring System with rear cross path detection is a safety option on 2022 Challengers for $1,390. It was first made available as part of the Driver’s Convenience Package for the 2011 Charger and the 2015 Challenger.


    MOPAR has a Blind Spot Detection Module for 2019-2020 Challengers. The part # is 04672783AA. It costs $590.40.

    There are some after-market kits out there that are ideal for older cars. Amazon, Walmart, and Crutchfield are three of the many retailers for after-market models. Expect to pay $300 to $500 for a solid system. If you have a Saturday to invest, you might want to install it yourself. However, it’s a fairly involved process. Having a kit installed professionally will cost at least $200.

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