My first experience with Collision Prevention Assist was in my boss’ E-Class. It was a small red light on the dashboard which I figured out came on when I got too close to cars in front of me while driving.

Then I got an A-Class and learnt a bit more about it. It wasn’t so basic. If it thought you might not be paying attention it would beep loudly (shout in my terminology) at you to warn you that you might be about to crash.

Then I heard stories from a colleague who says he was driving on the highway, came up behind a car and all of a sudden his car automatically slammed on brakes. And this was also the fault of Collision Prevention Assistance Plus.

Now I’ve had it beep at me many times, and with my CLA it has also actually lightly engaged the brakes, but not once has it been in an instance of real danger. In my opinion. It happens most often when you’re driving behind a car and they turn off the road you’re on, slowing down considerably. I however maintain my speed because I’m driving straight. The car doesn’t know they’re turning and so warns you of your impending demise.

It is however an important safety feature, and the one time it saves you from an accident will be worth all the false-positives.

Not too unhappy am I then when I turn on my car a few weeks ago to be greeted by a yellow message saying “Collision Prevention Assist Plus Inoperative”. I check the manual and it says I must drive slowly and take the car to a dealer. This is 16h00 the day before I’m supposed to go on a 3,000km road trip. So what do I do? I find a dirt road, check the ABS and traction control are still functioning and decide to take my chances. As far as I can tell the car functioned exactly as normal besides the lack of this one function. And it was actually quite nice, because with it inoperative, it was unable to beep at me.

Eventually though, several weeks after it started warning me I took it in to the dealership. They kept it for the morning and told me they did a software update, now the message is gone, hopefully for good.

From what I’ve read on forums and discussed with other drivers, it’s not an altogether uncommon occurrence amongst CLA and GLA drivers. And in most cases a software update fixes the problem for good.

Discalimer: When I took the car in the service agent told me if they couldn’t fix it they would have to keep it overnight, as they can’t let me drive with one of the safety functions malfunctioning. Fair enough. What it does mean is that I (and you) should definitely not drive an additional 3,000 km before taking the car to be checked out.