Blind spot detection (BSD)

Of all the assistance systems this is the one the CBR is strictest about: blind spot detection supplements your own observation, never replaces it. No warning is not proof that it is clear.

How does it work?

Radar sensors in the rear bumper monitor the zone beside and diagonally behind your car. If someone is there, a light comes on in the door mirror or the door pillar. Indicate while something is alongside and a stronger warning usually follows: flashing, a sound, or a vibration in the wheel.

Every brand calls it something different: Blind Spot Detection, Blind Spot Warning, Side Assist. That names differ is one of the principles the CBR names explicitly.

What the CBR asks about this

• You observe the situation directly yourself. The shoulder check stays mandatory, even when the light is off.
• You consciously choose whether to be supported; the system is an extra pair of eyes, not a replacement.
• You keep the sensors clean. A bumper full of snow or mud, or a bike rack, can block detection.

This system falls under these guidelines from the Rijprocedure B:

Limitations: This is where the exam questions are

Narrow vehicles are missed

Motorcycles, scooters and bicycles present too little surface to register reliably on radar. So precisely the most vulnerable road users fall outside its view.

Fast-approaching traffic arrives too late

A car closing at a big speed difference is sometimes already beside you before the system reports it.

A bike rack or trailer disrupts everything

Anything hanging behind or beside the bumper can either trigger the radar permanently or blind it. In many cars you then have to switch the system off manually.

The light is in your mirror, not in your head

The warning only works if you look at it. Anyone relying on a light they do not see still changes lanes blind.

Three practice questions

Open one for the answer and the explanation.

Your blind spot detection gives no warning. May you change lanes on that basis?

• No, you look over your shoulder yourself before moving over
• Yes, the system saw nothing so it is clear
• Yes, provided you also check your mirror
• Yes, but only in daylight

Correct answer: No, you look over your shoulder yourself before moving over

Explanation: The driver observes the situation directly. The absence of a warning proves nothing, certainly not for motorcyclists and cyclists.

Which road users does blind spot detection see least reliably?

• Motorcyclists and cyclists
• Lorries and buses
• Cars with a trailer
• Vehicles with their lights on

Correct answer: Motorcyclists and cyclists

Explanation: Narrow vehicles offer little surface for the radar. That is exactly why the shoulder check stays mandatory.

You have fitted a bike rack to the towbar. What does that mean for your blind spot detection?

• It can disrupt the sensors; in many cars you have to switch the system off
• Nothing, the sensors look sideways and not backwards
• The system actually becomes more accurate
• The system always switches itself off automatically

Correct answer: It can disrupt the sensors; in many cars you have to switch the system off

Explanation: Anything close to the sensors can cause permanent alerts or blind spots. You switch a system off when the system or the situation requires it.

Written on the basis of the official CBR Rijprocedure B. These are not real exam questions.