Dynamic Cruise Control
Thread Starter
Driver School Candidate
Joined: Jul 2009
Posts: 20
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From: OR
Dynamic Cruise Control
Today while driving at 55mph with dynamic cruise engaged, a truck slowed in front of me. He drove slightly to the left and then turned right to exit. My car slowed to match his decreasing speed but just as I decelerated to about 30 mph the braking stopped and the car attempted to resume to the original 55mph on it's own(the truck still in my path). I immediately stepped on the brake to keep from colliding with the truck. No collison, only a reaquantance with a very rapid heart rate.
Is the dynamic cruise supposed to cease functioning if it slows the vehicle to a set speed and then accelerate if an object remains in your path?
Howard
Is the dynamic cruise supposed to cease functioning if it slows the vehicle to a set speed and then accelerate if an object remains in your path?
Howard
CL Community Team
Joined: Aug 2006
Posts: 12,524
Likes: 216
From: San Francisco, CA
are you saying the truck veered to one side to prepare for the exit and the RX sped up before the truck exited? If this is the case,then most likely the radar couldnt see the truck anymore since it was no longer in the center of the lane. The car must have thought that the truck had exited already
Pole Position
Joined: May 2009
Posts: 2,838
Likes: 26
From: GA
Today while driving at 55mph with dynamic cruise engaged, a truck slowed in front of me. He drove slightly to the left and then turned right to exit. My car slowed to match his decreasing speed but just as I decelerated to about 30 mph the braking stopped and the car attempted to resume to the original 55mph on it's own(the truck still in my path). I immediately stepped on the brake to keep from colliding with the truck. No collison, only a reaquantance with a very rapid heart rate.
Is the dynamic cruise supposed to cease functioning if it slows the vehicle to a set speed and then accelerate if an object remains in your path?
Howard
Is the dynamic cruise supposed to cease functioning if it slows the vehicle to a set speed and then accelerate if an object remains in your path?
Howard
.
No, I don't play soccer!
Joined: Jul 2009
Posts: 6,652
Likes: 177
From: NJ
Howard, glad you're ok.
Dynamic laser cruise control only engages at speeds above 30 mph. Not sure if the opposite is true when the vehicle slows down to 30 mph or below. And it doesn't explain your acceleration with the truck in front of you. Did you happen to see what was displayed on the instrument panel (i.e. showing that dynamic laser cruise control was working)?
Dynamic laser cruise control only engages at speeds above 30 mph. Not sure if the opposite is true when the vehicle slows down to 30 mph or below. And it doesn't explain your acceleration with the truck in front of you. Did you happen to see what was displayed on the instrument panel (i.e. showing that dynamic laser cruise control was working)?
Thread Starter
Driver School Candidate
Joined: Jul 2009
Posts: 20
Likes: 0
From: OR
The truck veered slightly to the left similar to pulling into a tight parking space and then exited right. The truck as well as my RX slowed to aproximately 30 (sorry, didn't have time to pay attention to the display). My RX then accelerated in an attempt to resume speed before the major portion of 18 wheeler's trailer cleared out of my straight path. Had I not manually braked hard, I would have collided with the rear passenger side of the trailer in front of his rear-most tire.
CL Community Team
Joined: Aug 2006
Posts: 12,524
Likes: 216
From: San Francisco, CA
If it was a trailer, there also may have been some interference with a reflection of the sun from the metallic parts. There could be a lot of variables, from the car thinking that the truck was gone, or light reflection.
If the speed drops below 30, the cruise is supposed to cancel on its own and possible beep at you
If the speed drops below 30, the cruise is supposed to cancel on its own and possible beep at you
No, I don't play soccer!
Joined: Jul 2009
Posts: 6,652
Likes: 177
From: NJ
Wow, sounds pretty scary. I'm wondering if the higher clearance of the truck or the distance setting had something to do with it 
I've only used the dynamic laser cruise control once and it worked as expected. But I turned it off after a few miles because the roads are too congested by me. I'll have to give it a try again.
I've only used the dynamic laser cruise control once and it worked as expected. But I turned it off after a few miles because the roads are too congested by me. I'll have to give it a try again.
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Thread Starter
Driver School Candidate
Joined: Jul 2009
Posts: 20
Likes: 0
From: OR
RXSF:
No sun reflection, as it was overcast today. However, the other part of your response is precisely what I'd like to understand," the car thinking the truck was gone." If the presence of an object is determined by radar suffiently fast to calculate its speed, and adjust the RX speed, then why would it not reaquire the last 25% of the trailer and react accordingly. My guess is that it ceases reacting below 30mph, and if this is so can lead to a very dangerous situation -- as exemplified by what happened to me.
No sun reflection, as it was overcast today. However, the other part of your response is precisely what I'd like to understand," the car thinking the truck was gone." If the presence of an object is determined by radar suffiently fast to calculate its speed, and adjust the RX speed, then why would it not reaquire the last 25% of the trailer and react accordingly. My guess is that it ceases reacting below 30mph, and if this is so can lead to a very dangerous situation -- as exemplified by what happened to me.
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Thread Starter
Driver School Candidate
Joined: Jul 2009
Posts: 20
Likes: 0
From: OR
BTW: I was on hold with Lexus customer care for over 2 hours when I just gave up. I suspect the recalls have them busy. I'll talk with a couple of dealer service reps in a few days. I thought a heads-up for those who have the radar cruise was in order.
CL Community Team
Joined: Aug 2006
Posts: 12,524
Likes: 216
From: San Francisco, CA
howard, to clarify, you said that your car started to speed up again.
it is supposed to stop working at 30 mph, neither braking nor acelerating. If this was the case, then the car is acting normally. If its the earlier one, then something went wrong. But im sure Lexus has every possible scenario covered in the footnotes of the cruise control section.
My guess is that it ceases reacting below 30mph
Lead Lap
Joined: Feb 2006
Posts: 454
Likes: 2
From: ny
This was one of the reason I didn't get this dynamic cruise control. I don't trust it at all. If the radar didn't get a response from its signal, then it won't work. Just like you hit a ball into a gap of a wall, and nothing bounce back.
Lead Lap
Joined: Dec 2007
Posts: 557
Likes: 2
From: Midwest
We have dynamic/radar cruise on both cars (my LS40L and my wife's RX450h) and we love it. In fact, I will never buy another car without this option. It is SO much more comfortable/relaxing driving with this feature on the highway. Obviously, one always has to concentrate and keep your eyes on the road for any contingency plans.
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