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What Does BSM (Blind Spot Monitoring System) Mean?

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Introduction to Blind Spot Monitoring System

Accidents are pretty common when a car changes lanes. It usually happens when the driver does not notice a tilted vehicle that is not visible in the rearview mirror. Cars use a Blind Spot Monitoring system to avoid such accidents. It is also commonly known as BSM.


BSM(Blind Spot Monitoring) system works when the vehicle speed is 15 km/h or above. The radar mounted on the inside of the rear bumper detects a vehicle approaching from the side of the rear.

It causes the sensing direction indicator to be lit and displayed in the rearview mirror, notifying the driver. If the turn signal is operated in this state, the indicator will flash with an alarm, warning the driver to stop changing the lane.

How to Use the Blind Spot Monitoring System?

Using a BSM system is quite simple. That’s mainly because it works on its own. All you need is to follow its indications.

Let’s go through step-by-step how to use blind spot monitoring:

  • Keep a lookout on the blind spot monitoring system while driving.
  • Shift your attention when a vehicle enters the blind spot vicinity.
  • If the warning icon lights up, do not change the lane.
  • If the warning icon does not light up, double-check with your rearview mirror before making a turn or changing the lane.


Benefits Of a Blind Spot Monitoring System

Prevent Accidents

BSM can prevent fatal road accidents. They produce alert signals for the driver to help them make viable decisions. Hence, stopping you to collide in another vehicle.

Universal Systems

Most BSM systems are universal. That means you can install them on any car, regardless of its brand or model. However, there are also some specific blind spot monitoring system models for the vehicle’s type. So, it’s up to you to choose one of them

Reduced Stress

First-time driving is always full of stress – handling all fast traffic no doubt require practice. BSM can be quite helpful for new drivers as it reduces the burden of driving. It takes care of the difficult job of alerting you about an oncoming vehicle. Still, it’s best you monitor the side mirros at all times.

What You Should Know About the Blind Spot Monitoring System?

BSM (Blind Spot Monitoring) may have limited functions. For example, models of BSM only activates at certain speed. So, if the speed limit isn’t achieved, the sensors won’t alarm you. Therefore, it’s crucial you read the instruction manual of the blind spot monitoring systems to know such limitations.

It is important to know that BSM (Blind Spot Monitoring) is a safe driving-based system that aims to reduce accident injuries and the burden of driving. It’s best to not rely on it fully and also use your visions to be entirely safe from accidents.

For other important matters, please consult the staff or refer to the “Operation Manual.”

How Does the Blind Spot Monitoring System Work?

People often wonder how does this system work. How do they get notified of a vehicle that they cannot see? The one-word answer is radar-sensors.


The entire blind spot monitoring system is based on radar sensors. They are millimeter radar-based devices that monitor the roads. Their main job is to keep a lookout on all sides of the road. These sensors are designed to sustain themselves at even higher speeds.

That is why blind spot monitoring works even on highways. The sensors are connected to the notification lights. They trigger the alarm when they sense another vehicle close to yours.

Note that not all BSM systems use flashing lights to warn the driver. Many consist of audible warnings, like chimes or beeps. Similarly, some BSM systems are also based on haptic alerts. They trigger vibrations through the seats or steering wheel to issue warnings. So, it varies from a model to model.

Blind Spot Monitor may work in several scenarios. Here’s when:

  • When a vehicle is approaching your car from your adjacent lane.
  • When a vehicle enters your blind spot vicinity by changing its original lane.
  • When your vehicle is at a certain vehicle.
  • When the oncoming vehicles enter your radar’s range.

When Do Blind Spot Monitoring Systems Not Work?

Now that we know when a BSM system works, let’s look at when it does not. Here is a list of different scenarios:

  • When a vehicle is approaching you in the same lane.
  • When a car is coming from your opposite direction.
  • When a vehicle is moving two lanes away from your car.
  • When you cross non-moving objects on the road, like street lights, poles, guard rails, or parked cars.

What To Look For In A Good Blind Spot Monitoring System?

When buying a blind spot monitoring system for your vehicle, you should consider several factors. Here’s are some important factors to look for in a BSM system:


Adjustable Settings

Some BSM systems come with fixed settings. For instance, they have loud beeps or chime sounds. Additionally, their notification lights can also be quite distracting.

Hence, it would be best if you always opted for adjustable Blind Spot Monitoring. You can change the sound or light intensity. This way, you will not get overwhelmed by the system.

Indicator Location

Not every driver is comfortable with BSM on their side mirrors as they can block the view. Many people prefer a different location for indicator lights.

Luckily, blind spot monitoring systems can be placed inside the car. You can locate them on the A-pillar next to your vehicle’s window. If not, you can also place them on the side mirrors.

Speed Limit

Every BSM system has a different speed limit. That means not all of them can sense and alert you about a vehicle moving at very high speeds. So, it is better to opt for an option that helps you on highways and speedy roads.

What Is Rear Cross Traffic Alert?

Rear Cross Traffic Alert is commonly known as RCTA. It detects a nearby vehicle when you are reversing your car. This system comes in handy mostly when reversing out of a parking space. RCTA can help reduce car accidents by informing the driver about an oncoming vehicle on the rear side.


RCTA uses the same sensor framework as blind spot monitoring systems. It is an advanced driver assistance system to help you safely back out your vehicle. It activates when you put your car in a reverse gear.

According to a survey by Consumer Reports, over 85% of drivers were satisfied with having an RCTA system in their cars. RCTA (Rear Cross Traffic Alert) has many alternative names. You might know it as Rear cross traffic assistant, rear cross path detection, or rear cross traffic collision avoidance.

How Does RCTA (Rear Cross Traffic Alert) Work?

The Rear Cross Traffic Alert system consists of radar sensors, like BSM. These sensors are generally located on a car rear bumper’s right and left sides. They are connected to an alerting system. It could be notification lights or chimes.


RCTA triggers when a vehicle approaches your car from the rear side. Once it is inside your system’s sensing range, a signal is sent as your alert. The purpose of having sensors on bumpers is to monitor both sides.

Like Blind Spot Monitoring, RCTA also has speed limits. Most commonly, they only detect vehicles approaching at 0 to 5 km/h. This range may vary depending on manufacturers. Most RCTA systems use radar technology to sense traffic and trigger a notification.

Furthermore, RCTA systems come with different detection ranges. Generally, you will find options that monitor 120 degrees with each sensor. Alerts can also vary from system to system.

Conditions Where RCTA May Not Work

There are several conditions where the Rear Cross Traffic Alert system may not detect. Here’s the list:

  • Stationary objects, like parked vehicles, road signs, poles, walls, guard rails, lights, etc.
  • If the vehicle next to you is backing up.
  • When the vehicle is going away from your car in Reverse.
  • When a vehicle is moving at high speed, generally more than 12 km/h.
  • If it is a small vehicle, like a bicycle, motorcycle, etc.
  • If the approaching object is an animal or pedestrian.


It is safe to say that BSM and RCTA are very useful systems to have in a car. They can prevent serious injuries possible in road accidents. Blind Spot Monitoring and Rear Cross Traffic Alert notifies you about vehicles you cannot see from the side mirrors. Technically, they are in your car’s blind spots. So, there is no other way to see those vehicles beside blind spot monitoring systems.

Although BSM and RCTA have reduced the accident rates by a huge number, it is important to not reply on it entirely. After all, it’s a computer based system and a small error may lead you to unwanted incidents. For example, a faulty installation. An incorrect installation of BSM won’t detect cars. That’s the reason why the experts suggest giving the BSM and RCTA a test before trying it in real traffic.

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