I set 3 bars for a relaxing drive on fairly empty freeway; 1 bar for congested commute to work. The 4RX has braked for me at low speed once or twice (not on cruise control), and it slows to a safe distance always on cruise control, but similar to having another driver, you will tend to react differently to how the cruise control would when it comes to "panic" situation. I think the 4RX will keep things safe, but drivers may choose to slow down and/or speed up in a slightly different way than the computer would.

 

MB distronics plus seems the best amongst all others. I use it on highway all the time. maintain set distance from a car in the front and speeds up to my max set speed or slow down to a stop when traffic stops. Still I pay due attention. Another feature I like is "hold brake". Don't have to have foot on the brake pedal when I stop for red light for an example. In slippery winter time I prefer to control speed and braking myself. Another feature is an ability to detect sleepy driver with loud warning beep. (I think the feature monitors the movement of driver's head)

 

we have all that in the RX,
not sure why you are still hanging around here, not much to offer, and slam the rx every chance you get. also you had a gen3 ? and not a 4th gen. could hop in the 3rx forum ??
just thinking out loud

 

Former Lexus owner or possible future owner again is not allowed to stay in Club Lexus? I never heard something like this for any other forums(MB, Audi, BMW plus many others, non-related to automobiles)

 

He's just saying we are here to discuss our Lexus cars, not bash them and not brag how much better MB is or any other brand. We get it - you wanted "the best or nothing" congrats on that you got it.

 

 

I actually welcome comparisons from other brands. As Lexus owners who spent a large sum of money on an RX, I can understand most of us don't want to hear areas in which the RX is deficient. However, I am not brand loyal as I've owned about 10 brands. Since I am not all that happy with my RX, I want comparisons from other makes, so that hopefully I can make a better choice on my next car.

 

When I test drove a brand new GLE400, it had just been washed. Even so, the GLE prevented me from activating the system with an error message that the sensor was dirty and needed to be cleaned. So while I wasn't able to test the system, I was unimpressed by MB initial build quality and aging interior. Not sure I'd want to put my life or others at risk with an unreliable system (as I'm sure collision avoidance uses the same sensors).

The X5 was very aggressive and uncomfortable with the use of adaptive cruise control, and while the RX was not buttery smooth, you could tell that it erred on the side of safety, which is important as this is a relatively new technology.

Glad you like the MB system but you should probably back up the "why" with reasons other than features the RX already does. My two cents.

 

Every car, every brand has it's issues. My boss's brand new MB AMG - the big SUV whatever they call it - week two of ownership had to be towed to the dealer. Bad sensor or something - who knows but you get the point.

 

Of course, but the OP is asking specifically about the adaptive cruise control. Vibration and delayed shifts are considerably less frightening issues than failing sensors for example.

GLS is the biggest MB SUV. They mostly follow the A, C, E, S nomenclature of their cars but prefix their SUVs with GL, e.g. GLA, GLC, GLE, GLS, etc.

 

I have the exact same experience. Most of the time, I am able to brake before the ACC starts to slow down the car. ACC tends to slam brakes very abruptly and suddenly.

 

Interesting just-released IIHS study on driver assist technology and how they fare in the real world. Did not test Lexus (Tesla, BMW, MB, Volvo). Generally they perform but the study proves the need for driver vigilance.

IIHS Study

 

So this summer I drove our 19' RX 350 from VA to FL and back. I am a big fan of technology, so I used adaptive cruise control almost all the time. However, I ran into a situation three times where the system failed. It was during stop and go traffic. Speed was set to 60. The car was still and it sped up to close a gap opened by the the car in front of me moving forward then stopping. My car picked up speed, and continued to accelerate as if it couldn't see the car in front of it. Fortunately, the auto-braking system intervened and applied the brakes with the usual alarm avoiding an accident. This scared me and my family.

If this happened once, I would probably ignore it. But it happened 3 times. How is it possible that the cruise control was not able to see the car in front of me, and the auto braking system was able to? Are they not using the same camera and sensor?

In any case, this seriously shook my confidence in the system, and now I am reluctant to use it as I do not know if or when it might happen again. I had a higher expectation from a Lexus.

 

I don't trust the radar CC, so I just put it in regular cruise control mode and I decide when and how to slow down or speed up. Never had a problem.

 

What distance set were you on? I'm not comfortable on the minimum, most times the long setting slows me too soon, usually use mid-setting.