JSandro

This is supposed to be a standard feature. (even when cruise is OFF) The car should emit a warning and then break itself in severe situations.

See time 3:05 on this safety test video.

rbrylaw

Are you asking if anyone's car has done this? While we haven't let ours get that close to a rear-end collision, we have had the system beep and we were able to brake on our own, but I have no doubt the car would have if we hadn't.

larrypmyers

Several years ago I saw a video clip from Volvo demonstrating their autonomous braking capability.

The obstruction was a Volvo executive. Unfortunately, the system failed and the car knocked the executive down. Had the vehicle's speed been a bit higher the poor guy might have become road kill.

I'm confident today's systems work better, especially on the C.

GLCer

When we went to test drive our GLC, the salesman was keen to sell this safety feature to us as a standard equipment. My wife was impressed. So I asked him to test it out on a brand new GLC in the lot He looked back at me puzzled but took the challenge.

We drove to the back of the dealership and aimed our vehicle at a dumspter at approx 5mph-10mph. The GLC stopped and didnt hit the dumpster, even though he kept his foot on the accelerator pedal. We repeated one more time to see if it was a fluke. Sure enough it stopped but on both occasions, we did not hear any alarm or see the any warning sign on the dash. Not sure if it was a trick and I won't recommend you trying this at home.

I asked him if he tried this before, he said yes, when MB did a demo from them on a rack track but I was his first MB customer he had in 9 years who asked for a demo

internizzi

I have experienced this while driving on a highway. I guess I was going too fast and too close to the car in the front. While I did brake (somewhat lightly), the GLC didn't think it was enough, so the break pedal went in further by itself, I heard a warning beep in the process and the front seat belts tightened up. I believe that's the Collision Prevention Assist Plus and Pre-Safe functions at work. Pretty cool actually.

sblvro

Is there a magic speed number? I know in my ESCALADE it is 30 mph.

internizzi

Per GLC manual:
Vehicles without DISTRONIC PLUS: the autonomous braking function is available in the following speed ranges:
4 - 65 mph (7 - 105 km/h) for moving objects
4 - 31 mph (7 - 50 km/h) for stationary objects

Vehicles with DISTRONIC PLUS: the autonomous braking function is available in the following speed ranges:
4 - 124 mph (7 - 200 km/h) for moving objects
4 - 31 mph (7 - 50 km/h) for stationary objects

lin8810

For pre-collision warning and auto breaking, some competitors do require to turn on or activate cruise control. Which means if you are in city, slow driving without cruise control on, there will be no auto breaking.

How does Mercedes system work? I am potential GLC buyer and would really like to know if the system can detect/work anytime.

GLCer

On the GLC I did not read anywhere in the manual that says you have to be in cruise control mode. The autonomous braking and other safety features are activated each time you start the vehicle, and it works from 4mph. This is for USA, not sure if EU or elsewhere has different safety regulations.

Check out some of the Mercedes videos on youtube, its quite impressive. Autonomous braking and pre collission should be standard in all vehicles, everyone will be safer for it. We won't buy another vehicle without these safety features, unless its for track or racing

guido3

Has anyone noticed that CA alerts can be triggered by vehicles approaching from the side even though they do not enter your path of travel? I experienced this on 2 or 3 occasions when no vehicle was directly in front of me, but one fast approaching from the side at 90 degrees or so. Got the double beep and quick flash of red triangle but no brake action. Apparently, CA scans and recognizes potential moving hazards about to intersection your path of travel while you are moving. Any comments?

rbrylaw

Yes, both our C300 Sport and GLC300 will on occasion double beep when taking a curve with a car in our blind spot. My guess is because it may not be able to read the lane marker and going from straight to curve is sudden, so the car warns us. I'd rather be warned than not, so I've come to expect this.

nut854

Here's the Euro NCAP review on the GLC's autonomous breaking abilities for anyone interested.

http://www.euroncap.com/en/results/m...benz/glc/21987

Open up the Safety Assist menu and then expand AEB Interurban. Results look mixed. I looked up a Lexus to compare and the Lexus was able to avoid all collisions. I wonder if there are better sensors on some vehicles or whether they are intentionally programmed to be less aggressive.

http://www.euroncap.com/en/results/lexus/rx/22034

Either way, it's great that its a standard feature.

fabbrisd1

For pre-collision warning and auto breaking, some competitors do require to turn on or activate cruise control. Which means if you are in city, slow driving without cruise control on, there will be no auto breaking.

How does Mercedes system work? I am potential GLC buyer and would really like to know if the system can detect/work anytime."

For daily city driving - Collision Prevention Assist Plus is "active" all the time (unless manually turned off in the cluster) and YES it will bring you to autonoums full stop as listed above 4-31mph - if the driver does not intervene.

In Mercedes training - we drive approach a foil-covered-large-foam-block-wall at 35 mph - look to the side so not to trigger any braking reaction on drivers's part - and yes, the rig comes to a full panic stop - starts about 3-2 1/2 car lengths with alert - starts full braking activating ABS above 1/2 car lenght later - and the rig stops on dry/clean pavement about 4-5 ft from the barrier - so you know seems dang closer than you think.

If the driver after alerts hits full brake - reaction for most is not full stop - so BAS steps iun to provide full-stop-ABS braking.

If driver hits the brake - then releases brake - you're screwed.

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Distronic/Driver's Assist is another kettle of fish - you forgo CPS+ for different set of highway safety/convenience features.
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Of the safety systems out there - as compared to the Japanese "brake light ahead" visual systems - those are sh*t really
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ALL added safety systems have their limitations - and frankly "alerts" as provided by CPS system to me are all to the good - since there are a lot of other goofy driver's in other vehicles out there - and I would prefer to be "alerted" than in today's multi-tasking enviorment as compared to no alerts.

---------------------------------------
The Mercedes salesman who did the dumpster test with customers in the car should be shot - he can do the test and have you watch, with his management's approval - but having you in the car is strictly forbidden by MB policy - period.

I hope he took the opportunity to explain MB BAS+ to you - as well as MB's ABS system with 40% higher freq/cycle on ABS than the Japanese safety standard - if he didn't - then he needs to go back and learn his MB safety stuff

mdsbuc

fab, can you go into a little more detail about this comment? Are there some negatives in choosing D/DA vs. the standard CPS? Thanks.

JSandro

Yes, fab.. please do. This is my issue. I have D/DA option package and the dealer said that CPS is NOT installed. Fine. But, D/DA is supposed to have what's called 'Pre-Safe Break" instead (with pedestrian recognition and cross traffic alerts as well, so CPS on steroids) Pre-Safe break, from what I read, also does the autonomous breaking. But again on my car in does not work. The car does NOT auto break. Dealer tested it. Ran diagnostics etc and all should work, but it does not auto break.

"pre-safe break" shows up in my instrument cluster and is selected "ON"

Any insights would be super helpful!

cyber3d

Pre-safe brake is not autonomous. Your foot has to be on the peddle and you must have pressure on it. If the car senses an obstacle it will apply the proper amount of braking in situations where you don't apply enough yourself.

The system errs on the conservative side. I came up on a stopped car a tad too fast and Pre-safe took over and applied the proper amount of pressure to stop in time whilst considering road conditions. Personally, I think I could have stopped in time myself.

jonosc

I'm currently having the same problem with my 2016 C450. D/DA is installed but CPS+ has NEVER warned me or auto braked since purchase. All the C450's I have seen/driven do NOT have the CPS settings/menu like mine either.
First time dealer checked car they said there are no error codes - so it's working! But the C300 Loaner was always warning me, and my E350 without D/DA is always warning me. My car auto breaks in Distronic/Cruise no problem, it's weird but I suspect that this is a software issue (not installed or bad controller).
I was planning on getting a GLC (my 8th Mercedes) but this has put a halt to my new car until I know these systems work. The car is booked into the dealer in two weeks to fix this, so hopefully I should have some answers then.

MITCH1975

I pushed it a little the other day and the warning buzzer went off. I broke at that point as I did not want to risk it. But at least the buzzer went off. Nice.

shutterfly

did an inconclusive diy test today.
I put an empty cartoon box, about 4ft tall, 3 ft wide in the front, and started my GLC and ran at it.
The vehicle speed was at about 7mph when it was about 3-4 feet away from the box, and nothing happened autonomously. The car crashed into the box.

But the other day the audio warning did go off when the vehicle suddenly slowed down and I was getting too close. So partially I knew CPAP did work.

As to why my experiment failed, I guess it's because the box is not big enough? Or it's made of paper, not like those harder objects that would bounce back enough radar wave?

At least I learned we still need to be responsible drivers and not count on those bells and whistles.

cyber3d

Thought this might be interesting. 2 videos. One of the CPA+ Collision Prevention Assist Plus
http://techcenter.mercedes-benz.com/...us/detail.html

BAS+ Braking Assist System Plus (with cross traffic detection).
http://techcenter.mercedes-benz.com/...st/detail.html

Here is the text from MB regarding "autonomous braking"

The COLLISION PREVENTION ASSIST PLUS driver assistance system evaluates the information from the radar sensor system installed in the vehicle.

If the distance to the vehicle ahead falls below a safe distance for several seconds, first of all COLLISION PREVENTION ASSIST PLUS draws the driver's attention to this fact by means of a warning symbol in the instrument cluster. If the distance decreases further, an intermittent tone also sounds. In the case of critical braking situations, Adaptive Brake Assist helps the driver with the best possible brake pressure.

The system automatically performs partial brake application if a risk of collision persists and there is still no reaction from the driver. This reduces the speed considerably and the driver is also given a physical warning. This autonomous braking application may be sufficient to prevent a rear-end collision, depending on how fast the vehicle is approaching the vehicle or obstacle ahead. If a collision is no longer avoidable, the braking process will considerably reduce the effects of the accident.

An optical warning is given if the distance to the vehicle ahead falls below the safe distance at speeds between 30 and 250 km/h; the optical and acoustic warning is given if there is a danger of collision at speeds over 7 km/h. Adaptive Brake Assist is active at speeds between 7 and 250 km/h for moving objects and between 7 and approx. 70 km/h for stationary obstacles. Autonomous partial braking is also available for moving objects at speeds below 105 km/h, and in conjunction with DISTRONIC PLUS up to 200 km/h.

guido3

Thanks, cyber3d -- a much better sorting out of the various safety systems than even a thorough reading of the operator's manual provides. Not that it matters a lot which specific system (of the core group of systems) is responsible, but I now finally understand that the occasional cross-traffic warnings I'm getting are actually a function of the BAS+ not the CPA.

cyber3d

Whoa. Brake assist worked great today. Freeway speeds when car in front suddenly braked. Had foot on brake pedal, but then they slammed on their brakes and the GLC took over and applied even more braking. It was very cool.

glj86

I sure hope mine never autonomously 'breaks'! :-)

JEVA

I was showing a friend at lunch the distronic self driving feature when the car ahead of me decided he wasn't going to make the light and slammed on the brakes. The GLC braked pretty hard and stopped in plenty of time but it was pretty impressive. It took all my willpower to override my instinct and not hit the brakes myself.

JSandro

Right. When distronic is active it works great. With distronic off (i.e. cruise control off) it will not do this, unless you have your foot already applying some pressure to the break. It is supposed to break autonomously no matter what. And, it does not.