I just purchased a new 2016 RDX Elite (Advanced in the US) in the last week of June, and as a technology Geek I am very impressed with all the various systems, and I am trying to fully understand them to get the most out of them.

The thing I am having trouble with is Forward Collision Warning (FCW) and Collision Mitigation Braking System (CMBS).

Are these two separate systems? If they are two different systems, do some cars have one and not the other?

I have read some material that says FCW uses the camera to detect things like pedestrians which would not be recognized by radar. I have also heard that FCW will only create a warning , but will not perform any braking.

I understand that CMBS uses radar to determine if my RDX is rapidly approaching another vehicle, and it will also create a warning in the early stages. As the RDX gets closer to the vehicle in front it will apply the brakes slightly and tighten the seatbelt. In the final stage it will apply the brakes more powerfully and attempt to stop the RDX.

The big reason for my question, is that I'm not sure these systems are working correctly on my RDX. I have read elsewhere on this forum about owners turning off the CMBS due to frequent false warnings. I rarely get a warning even when deliberately approaching another vehicle at a good speed. In fact if I wasn't already holding my foot just above the brake pedal, it would have been impossible for me to react in the short warning time I was given. I have the warning distance set to "long" by the way.

I also covered the windshield camera with black electrical tape, and although LKAS and LDW stopped working, the "BRAKE" warnings continued the way they did previously ( very infrequently and with insufficient warning time). This particular test seems to show that my camera is not involved in these systems. Either that or my RDX does not have FCW at all.

I talked to the dealer about this. His diagnostic tests showed no diagnostic codes, so he declared the systems were working properly. He also said I would only get the warnings if I was pushing down on the gas at the time. Since he told me that I have received one warning while coasting, and another visual warning while my foot was lightly on the brake ( but no audible alert in this case)

I would really like to hear other owners describe how their systems work. Do any of you feel the system does not give sufficient warning time? Has anyone felt their seat-belts tighten up as described in the manual? Do any of you get frequent false alarms, and if you do, what driving situations cause them? If you can describe a situation which constantly causes a warning, I would like to duplicate it, in order to test my own vehicle.

 

I have the same question as you. And, I've done the same experiments as you -- coming up on a stopped vehicle and getting very close before braking.

But, my system did come on once -- full force. It occurred at a time when there was no danger, as I saw it. My foot was on the accelerator (may be an important part of the equation), the car quite a way in front of me slowed rapidly to make a left turn. The car was well through the turn, and I still a long ways from it, when the Acura gave a warning and applied heavy braking.

Never was anywhere near the other car, as I said, but the Acura "saw" something it didn't like.

Upon reading the manual (to the degree it is possible for a mere mortal to read those encyclopedias), I found it clearly states that the car is "looking" for a decelerating vehicle in same lane. I.E. it's looking for changes in other car's speed.

I had a couple of warnings with no braking early on. Those were also associated with cars in front of me slowing from their previous speed.

I actually turned the system on and off today to be sure it was still on. It was. But, I haven't had an alert in a while.

My guess is that I've been so focused on driving smoothly to see what kind of gas milage I can wring out of this thing, and that has resulted in no close encounters of the Acura kind.

I'm gonna give it more time to see if the algorithm reveals itself to me. It could be that the system is drawing information from the car's learning my driving patterns. Again, it happened early on but hasn't recently and doesn't deploy when I intentionally come up on a stopped car. (again, foot on/off throttle may be part of the contingencies).

 

I have looked in the owners manual, but could not find that reference. My Canadian manual says this:

The system starts monitoring the roadway ahead when your vehicle speed is about 3 mph (5 km/h) and there is a vehicle in front of you.
The radar sensor is in the front grille.
The CMBS activates when:
● The speed difference between your vehicle and a vehicle or pedestrian detected in front of you becomes about 3 mph (5 km/h) and over with a chance of a collision.
● Your vehicle speed is about 62 mph (100 km/h) or less and there is a chance of a collision with an oncoming detected vehicle or a pedestrian in front of you.

Mine also seemed to alert more often during the first week of ownership. I know there are adaptive transmissions that hold the gears longer as they learn the drivers habits, but since this is a safety feature, I don't think they would automatically decrease the sensitivity for drivers who like to brake hard at the last minute. That could cause a problem when someone borrows your car.

The manual also seems to use the terms FCW and CMBS interchangeably. For example when describing the setting for Forward Collision Warning Distance, it says this setting "changes at which distance CMBS alerts".

 

I have a Tech (Canadian), that I got at the end of June. So far, the system seems to work fine, but I only have 2000km on the car. The CMBS has come on only a few times, in instances I would say were warranted (merging into heavy traffic and being close to the car in front of me, for example). The FCW has worked well, except for one particular case: there's a small bridge in my city with a fairly big arch, and every time I drive on that bridge, I get a "Brake" warning just before I start driving on the arch, even tough there's no car in front of me. Guess it's fooling the system.

 

In the U.S. I only see a reference to CMBS. This is what the online doc says:

To help reduce the likelihood or severity of a frontal impact, the AcuraWatch Plus Package features the Collision Mitigation Braking System™ (CMBS™)61

Powered by a combination of radar transmitter and forward-facing camera, the CMBS™ determines the distance and closing speed of detected objects that lie directly ahead.
To alert the driver to apply the brakes, the system will, if time allows issue a beeping sound and flash an amber “Brake” message in the Multi-Information Display.
If you do not take action to reduce speed, the CMBS™ automatically begins light braking.
When the system senses that a frontal collision is unavoidable even if no prior alerts have been given, strong braking is automatically applied to help reduce the impact velocity and collision force.
The goal of the CMBS™ is to alert the driver to apply the brakes. While the system assists, it is not expected to avoid a collision on its own.

I have seen the amber "BRAKE" message a couple of times when I was close to a car. To me it seems to be working as expected. I have a 2016 RDX tech with Acurawatch.

 

And the Canadian site mentions both FCW and CMBS. Despite many differences in available options between the US and Canada, I think the AcuraWatch features are the same.

The image which can be downloaded from this site, describe the two features this way:

CMBS
This available system can brake the vehicle for you if you don't slow down when a risk of a collision with a vehicle or pedestrian is detected.

FCW
Above 10 MPH, this available system can trigger alerts if it determines you are in danger of a collision with a vehicle detected ahead.

Although the names of the systems are different , their functions are pretty darn close.


I have seen the same message when I get a little too close to another car while on the highway, but when I am approaching another car at higher speeds ( a parked car for example) I don't think I would have time to react if my foot was not already being held above the brake pedal. In other words I seem to get the warning if I am slowly decreasing the gap between me and the vehicle in front, but the alert is much too late when closing the gap at higher speeds. My experience with ACC ( adaptive cruise control) proves to me that the radar can detect the vehicle in front when I am about 6 car lengths away (usually about 4-6 seconds of space), but I only get the CMBS warning when less than 1 second from hitting the vehicle in front.