Understanding ADAS: Blind Spot Monitoring

blind spot in rearview mirror

Check your blind spot!

Blind spot monitoring (BSM) used to only be available on high-end luxury vehicles. Now, this blind spot technology is offered by midrange and even budget brands. If your current vehicle doesn’t have blind spot monitoring, your next is more likely to.

As automotive technology progresses, these advanced safety systems will be encountered more and more by drivers and auto service pros. In this post, we’ll explain blind spot monitoring, show 4 examples of how it appears on the road today, and provide 3 best practices for handling automotive blind spot detection systems.

What is Blind Spot Monitor (BSM) in a car?

Have you ever been driving on the freeway, decided to pass a slower vehicle, checked all your mirrors, checked your blind spot over your shoulder, and started switching lanes, only for a car to appear out of nowhere from your blind spot?

Blind Spot Monitoring (BSM) is an advanced driver assistance system (ADAS) that aims to reduce crashes that happen when you are switching lanes and a car is in your blind spot.

So, what is BSM in a car?

BSM systems inform drivers when another vehicle is in their blind spot. Depending on your system, this could be an indicator light on the dashboard or side-view mirrors. BSM and blind spot warning (BSW) system work together to identify a risk and warn the driver through a visual or audible chime. Some warning systems even include a seat or steering wheel rumble.

The goal of blind spot monitoring and warning systems is to make changing lanes and merging safer. BSW would affect half a million (8.7%) blind zone and lane change or merge-related crashes each year, according to the National Highway Traffic Safety Administration. As it is now, this technology is already reducing crash rates and lessening their severity, resulting in 14% fewer lane-change crashes and 23% fewer lane change crash involvements with injuries, according to a report from the Insurance Institute for Highway Safety.

How does Blind Spot Monitor work?

Blind spot monitoring systems use radar sensors, rear-mounted ADAS camera sensors, or both to monitor when a vehicle is approaching from the rear and entering your vehicle’s blind spots.

blind spot system diagram

Once detected, a blind spot warning (BSW) alerts drivers through an indicator on (or near) side-view mirrors, the steering panel, audible or haptic warnings. Some systems provide stepped tactile warnings and different notifications if you activate the turning indicator in the direction where a car is in your blind spot. 

Blind Spot Technology Variations to Know

While each individual OEM has its own terminology, you will see many Blind Spot Monitoring (BSM) systems and technologies. The following list contains terms that are often referred to synonymously with BSM:

  • Blind Spot Warning (BSW)
  • Blind Spot Detection (BSD)
  • Blind Zone Detection (BZD)
  • Blind Spot Information (BSI) System
  • Blind Spot Collision Warning (BCW)

Beyond these similar systems, there are a few related ADAS technologies in the same vein, but with different capabilities. Because its important to know how these systems differ, here are the basics:

Blind Spot Assist

Also known as: Blind Spot Intervention, Blind Spot Collision-Avoidance Assist

The key difference between blind spot monitoring and blind spot assist is that the latter actively assists the driver. It uses the vehicle’s brakes and steering to avoid a collision.

It would make sense then, why monitoring, warning, and assist systems are bundled together. They work in tandem. BSM systems constantly monitor blind spots and warn you when cars are in them. Some provide audible warnings when your blinker is on and a car is in your corresponding driver-side or passenger-side blind spot. If you don’t respond to reduce the crash risk, some, more advanced systems add active crash intervention to safely avoid a collision. The driver can take over from the car at any time.

Lane Change Merge

Also known as: Lane Change Assist

Lane Change Merge is another ADAS that works to help the driver to make safe, intentional lane changes, with the turning indicators activated. It takes BSW a step further, with the ultimate goal of safe lane changes.

4 Real Examples of Blind Spot Monitoring and Related Systems

Learning about ADAS is challenging. It’s jargon-heavy and automakers present blind spot systems in many different ways. On top of that, BSW is often bundled together with other safety systems. To help understand and recognize real-world applications, here are 4 examples of blind spot tech available on the road.

1. Subaru Blind-Spot Detection and Lane Change Assist

Subaru’s Blind-Spot Detection system is available on most of its 2021 models, including the Legacy, Outback, Crosstrek, WRX, Forester, Impreza, and Ascent. Here’s how Subaru describes it:

“Using radar sensors, the Blind-Spot Detection system warns you with a visual indicator in each side mirror if a vehicle is sensed in your blind spots. Another feature of this system, Lane Change Assist, alerts you with a flashing indicator in each side mirror if it senses a vehicle approaching in a neighboring lane while you signal for a lane change.

And, because blind spot sensors are monitoring the rear and back of the vehicle, Subaru also bundles this technology with Rear Cross-Traffic Alert, an ADAS feature that alerts drivers if traffic is approaching from the side as the car is in reverse.

2. Ford BLIS with Cross-Traffic Alert

Ford’s Blind Spot Information System (BLIS), with Cross-Traffic Alert, is another example of BSM in action. From the Ford Co-Pilot360 Driver Assist Technology package, BLIS is available on many 2020 models — Mustang, Fusion, Escape, Explorer, Edge, Flex, Expedition, Ranger, Super Duty, and F-150. Here’s how Ford describes its system:

“BLIS® (Blind Spot Information System) can alert you to a vehicle detected alongside and difficult to see in a blind spot. The system uses radar sensors on both sides near the rear of the vehicle. When a vehicle is detected in your blind spot, you are alerted with an indicator light in the sideview mirror. The Cross-Traffic Alert feature also uses this radar to help detect traffic behind your vehicle when you’re slowly backing out of a parking spot or driveway. When it detects a vehicle approaching from either side, it flashes an indicator light in the sideview mirrors (same as BLIS) and emits an audible warning. Also, a visual display in the message center indicates from which direction the vehicle is coming.

Note: For trailer towing-capable models, it’s important to know that BLIS can still monitor blind spots, but the rear cross-traffic alert will not work when you are towing a trailer.

3. Mercedes Blind Spot Assist with Exit Warning

Mercedes offers Blind Spot Assist with Exit Warning standard on most of its 2021 lineup, while Active Blind Spot Assist is optional. Here’s how Mercedes describes it:

“When traveling above approximately 20 mph, radar technology can help sense when a vehicle enters the blind-spot area. Blind Spot Assist can then alert the driver via an illuminated red icon in the appropriate side mirror. An audible warning sounds if the driver activates a turn signal while a vehicle is detected in the blind spot. After parking, Exit Warning Assist can alert the driver or passengers to vehicles, cyclists or pedestrians that could be at risk if the door is opened.

Mercedes’ 2021 Driver Assistance Packages are optional on most models. They offer an additional Active Blind Spot Assist feature. The difference is that when you start to change lanes, “active technology can help guide the car back by selectively braking individual wheels.”

4. Kia Drive Wise Blind Spot Features

The Kia Drive Wise ADAS package offers a few related blind spot features: the Blind Spot View Monitor system, Blind-Spot Collision Warning, the Blind-Spot Collision Avoidance Assist.

When the turning signal is activated, the Blind Spot View Monitor System shows the digital footage of your blind spot on the screen in the display panel. “The Blind-Spot View Monitor (BVM) System is designed to display the rear and side of the vehicle blind spot areas in the Instrument Cluster LCD when the system is activated,” says Kia.

Kia also offers a Blind Spot Collision Warning (BCW) and Blind Spot Collision-Avoidance Assist (BCA). Here’s how Kia describes its Blind-Spot Collision Warning (BCW):

“The BCW system uses radar sensors in the rear bumper to help alert the driver in certain situations if it detects an approaching vehicle in the driver’s blind spot area.

The system will activate when the vehicle is traveling faster than 20 mph and will alert the driver if another vehicle is detected by the radar sensor.

1st-stage alert: When another vehicle is detected within the BCW system warning boundary, a yellow indicator will illuminate on the outside rearview mirrors.

2nd-stage alert: When 1st stage alert is on and the driver activates a turn signal, a flashing yellow indicator will illuminate on the outside rearview mirrors and the system will sound an alert.

Kia’s active version of its Blind Spot Collision-Avoidance Assist (BCA) initially uses the BCW system’s 1st and 2nd stage alerts. When the 1st and 2nd stage alerts have been activated, but the risk of a blind spot collision has since increased, “braking is applied to the opposite side front wheel and a visual warning occurs.”

Blind Spot Monitoring Best Practices

ADAS poses challenges for drivers and repair pros alike. To help fill this knowledge gap, let’s look at things from a few best practices when it comes to driving and working with a BSM-capable vehicle.

Know what to expect from your car’s BSW.

Know how your car’s blind spot monitoring or assist system is supposed to work. Remember where to expect alerts. It’s especially important to be aware of whether your system provides autonomous active assistance. It’s helpful to think about what has to happen for your BSW to go off. Do you have to reach a certain speed? Will it work when your turning indicator is off or just when it’s activated?

BSM is a safety system, not a fully autonomous car.

All car companies offer some sort of disclaimer about their ADAS systems. Basically, they say that while ADAS systems are made for safety, they can’t stop all crashes and they shouldn’t be relied upon to do so. Knowing the technology’s limits is important. For example, AAA found that it takes BSM systems 26% longer to detect motorcycles.

Understand when vehicles need calibration.

Blindspot warning systems reduce crashes and injuries by providing alerts to drivers. But, they can’t stop every crash. When a crash happens — even one that doesn’t directly involve the rear of the car — radar sensors and cameras need to be professionally recalibrated so they are accurately monitoring the vehicle’s true blind spot. Blind spot monitor calibration is just one part of any ADAS calibration service. Knowing when to calibrate ADAS cameras and sensors is key to keeping blind spot monitoring systems working the right way. Common error messaging includes the following:

  • Blind spot monitoring malfunction
  • Blind spot warning failure
  • Reset blind spot monitoring
  • Blind spot warning sensor blocked
  • Blind spot collision warning error
  • Blind spot warning error
  • Blind spot alert temporarily unavailable
  • Blind spot alert unavailable service required
  • Blind spot detection unavailable
  • Blind spot detection disabled – radar blocked
  • Blind spot alert temporarily unavailable

If your vehicle is giving any of the above notifications, it could be a good sign that your car’s ADAS system needs to be professionally calibrated.

The ADAS Calibration Specialist

Car ADAS is the vehicle calibration specialist, calibrating all types of ADAS systems at its National Training Center in Salt Lake City, Utah. Interested in ADAS calibration as a new revenue stream? We provide ADAS calibration solutions, helping our customers open and operate ADAS calibration centers. Contact Car ADAS Solutions to learn more.

Share this post

Related Articles

Subscribe To Blog Updates

Get notified when a new blog post is released!

Own Your Own ADAS Calibration Center

Enjoy high profits in an industry that is growing exponentially!