bigh123

Can someone remind me, why does the ML have this and not the e class? Also, isn't there something similar to this for the e class?

BenzV12

I think Distronic Plus should do what you mentioned considering it automatically adjusts the distance between you and the car ahead according to the set speed

hyperion667

too Hang up and drive is a really good collision prevention too

mitaka

Mine has it... Isn't it called PreSafe or something like that on the E Class

bigh123

It sounds very similar to it, but why name it something. Just for marketing? Can cause consumer confusion (like in my case).

Live Oak

I had it work yesterday. On an Interstate, a car pulled in front of me, reducing my comfortable following distance. I was backing off when another car pulled in front of him causing him to slam on his brakes. A collision impending . . .

PreSafe recognized the rapid approach to the car in front of me and was on my brakes before I could get my foot to the brake pedal. It gave me the classic Mercedes two-beeps as it was doing it, and tightened my seat belt.

Everything turned out fine. I didn't really need the PreSafe, but had I been daydreaming, it really would have helped prevent a collisiion or reduce the seriousness of one.

bigh123

The beeping sounds like prevention assist. The only difference I can see is that prevention assist is working even when cruise control is not on. However, the current alarms for the e350 require you to turn on cruise control (which kinda sucks since you want the prevention alarm when not using cruise).

ttoE550

My pre-safe in the 2010 E550 works without cruise control. All cc does extra - if you have Distronic+ - is begin slowing the car down earlier according to the distance set.

BenzMan369

PRE-SAFE has nothing to do with preventing a collision. It does work in conjunction with the car's collision avoidance systems, to automatically increase occupant protection when a collision may be imminent. PRE-SAFE takes the following measures depending on the hazardous situation detected:

The front seat belts are pre-tensioned.
It adjusts the front-passenger seat if it is in
an unfavorable position.

The air pressure in the side bolsters of the
seat cushion and seat backrest of the front
multicontour seats is increased.

If the vehicle skids, the panorama
roof with power tilt/sliding panel (or, presumably, the standard
power operated roof if so equipped) and the
front side windows are closed so that only
a small gap remains.

If the hazardous situation passes without
resulting in an accident, PRE-SAFE slackens
the belt pretensioning. The air pressure in the
side bolsters on the multicontour seat is
reduced again. All settings made by PRESAFE
can then be reversed.

Amazing stuff.

Live Oak

Pre-Safe Brake DOES, as I described. And, I might add, without cruise control running.

BenzMan369

Yes, that's correct, but Pre-Safe Brake is not the same as your originally referenced Pre-Safe, believe it or not.

Bigh123 has it right, MB seems to delight in creating multiple intricate systems names resulting in consumer confusion. All with the best of intentions, of course.

"Pre-Safe" is a part of the vehicle's Occupant Safety Systems. It does nothing to apply automatic braking in emergencies.

"Pre-Safe Brake" is a separate function and is part of the vehicle's Driving Safety Systems. It does indeed provide for automatic braking to slow the car down and give you time to fully stop the car or take other evasive action. It should also give you both visual and audible warning, as you probably already have experienced.

"Pre-Safe Brake" is only available on cars equipped with the Distronic Plus Driving Safety System, which I assume your car has.

It's all spelled out in the four billion page Owner's Manual.

Don't mean to argue or quibble over terms, but, since vehicles may have Pre-Safe, but not be equipped with the extra-cost D+ option and therefore don't have Pre-Safe Brake, IMO it's important that others reading the thread whose vehicles are not equipped with D+ (like me, e.g.) don't expect their vehicles to automatically brake in collision-imminent situations merely because they have Pre-Safe.

WEBSRFR

Great story. What is especially nice is in a panic situation, the car figures out just the right amount of brake force to apply no matter how hard or soft you apply the brakes. Not so sudden that the guy rear ends you and not so slow that you hit the car in front. In fact I think it is especially designed to not hit the car in front but leave as much space as possible for people behind you for your safety and that of others. What a great system!

Too bad this is not in more E class vehicles. Distronic and the radar sensor is an extremely rare option. It is really a feature that can save your life. This is even very rare on most S class vehicles out there. I always envy someone when I see the little glass cover on their grill...

BenzMan369

Thanks for this. Very well stated IMO.

I should have commented to LiveOak how valuable and reassuring the posting of his experience with D+/Pre-Safe Brake is, especially to those of us who don't have it. It's an option I will now definitely consider on my next car.

So LiveOak, thanks for your story. No matter what you call the system, it worked!

Arrie

Pre-safe brake in my 2010 E550 works as follows:

If the D+ radar sees a danger of collision it gives a double beeb warning 1.5 seconds before the collision would actually happen. If I touch the brake pedal after the warning the car applies 100% braking power.

If I don't touch the brake pedal the car will automatically apply 40% of braking power 0.5 seconds before the collision. This means that the collision will happen but with less impact.

Above functions have nothing to do with cruise control being on or off. This is enabled at all times as long as you have the pre-safe brake enabled in the cluster selections.

There is a very good video in the utube explaining this.

BenzMan369

Amazing stuff Arrie. Thanks for the expanded explanation and the video heads-up.

D+ gets an A+ from me.

Arrie

An A+ from me too. I have experienced the double beeb twice and the car does a real good job applying the brakes when I step on the pedal.

I obviously remembered the times wrong. The double beeb comes 2.5 seconds before the collision and if I don't touch the brake pedal the 40% automatic braking starts 1.5 seconds before the impact.

I could have sworn that I read somewhere it is 100% braking power when the pedal is touched after the double beeb but the wideo in the below link says it adjusts the braking power depending how much time it has left to stop the car. For me it sure felt 100% braking during both times I experienced it.

Arrie

Here is even a better video explaining the Pre-Safe brake system.

It has some other stuff at the beginning but the later part is the Pre-Safe stuff.

WEBSRFR

This is a great system but now all Mercedes has to do is bring the stopping distance in line with Audi, BMW, and Jaguar.. i.e. about 110 feet from 60 to 0. It will make this system even more effective.

I'm really surprised that from the W211 to W212 the stopping distance did not change much and is around 125 feet. About the same as the huge Volvo XC90 SUV...

BenzV12

Thanks for the videos very informative
Still, there is something that bugs my mind so it didn't fully stop the car in the last part of the 1st video ,actually MB should make a system that automatically stops the car even if you don't apply brake let alone that you acclerate towards the obstacle it still cuts the power and brakes the car may be next gen will call ULTRA Safe

I see, they don't wanna rule out the drivers involving but it's better to prevent an accident , collision ,rear end rather than it happens at minimal damage

Arrie

I think it is a safety feature that it does not apply full brakes if you don't touch the brake pedal yourself. In addition to the two true events I experienced where an accident could have happened and I prevented it by touching the brake pedal I have received the double beeb warning three times where there was nothing in front of the car, at least that I could see. I did not touch brake pedal and the car did not apply the 40% braking either.

I don't know what happened but it could have been a large size bug that the system saw but as it went away immediately it did not apply the brakes? If the car would automatically do the full braking without your input it could make the car wery unpleasant to drive.

I think it is coming though after they figure out how to make sure the danger for the accident is real, like installing two radar units in opposite sides of the front of the car and treating it as accident danger if both radars see the danger at the same time. This would eliminate the bug problem as that size bugs hardly exist to cover both sensors in the front at the same time.

ttoE550

I have never experienced the bug problem, but there are times the system gets "fooled." One common one for me is when I am approaching a stop light and there is a dedicated left-turn lane directly in front of me - my lane curves around the left-turn lane. The car assumes I will be going straight and sees someone waiting to turn left. It thinks I do not see it, so it gives me a double beep. I know it's going to do this, so I am ready to override with the throttle. To have the car apply 100% brake here would be very dangerous indeed, and could produce an unnecessary accident.

The car will also double beep on residential streets if there is a car parked on a left-hand curve. I think for some reason the parked car prevents the system from seeing the curve, and so again it assumes you will be driving straight into the parked car. Again I would not want 100% braking here.

bigh123

Thanks for the info. I'm getting the driver assist on my new 2013 e350. Can't wait to see how it works. Hopefully MB knows about the false positives and will adjust the system.

ttoE550

I think the system would need a huge jump in capability to handle these things. Maybe, but I doubt it. The thing is that you get used to the things that normally happen, and overriding the system becomes automatic.

Another tricky false positive for blind spot assist: turning left or right from the center when multiple lanes turn the same direction. Blind spot assist thinks you are turning into the car at your side, when really the car is turning too. If you get the system that brakes to try to correct the steering, you better be holding on tight! I have no idea how the engineers could correct for that unless the car could somehow read the tire angle of the car beside you. Yes, blind spot assist shuts off at low speeds, but I have gotten this false positive many, many times - I guess our intersections are big enough that we are probably doing 30+mph in the turn.

bigh123

If you have blind spot assist, can you turn off the assist part and just make it blind spot detection so it doesn't screw with your braking?

ttoE550

I would assume so, but I don't have the assist - sorry, I get confused on the names. My car is 2010, so it is just detection.