So, yesterday I was on my way up to see my cousin in WV in my LS460L equipped with radar cruise and the Pre Collision System (PCS). Theres a section of highway at the interchange of I-70 to I-81 where they are doing a ton of construction, its pretty rough and the road heaves and transitions from asphalt to concrete and back again.

Well...something must have tricked my PCS into thinking I was about to hit something (Nothing was remotely close), and the car slammed on the brakes at about 50 MPH, tightened the seat belt, beeped and flashed at me. Luckily, nobody was behind me...

Our 14 Jeep Grand Cherokee had PCS and did that to me once, but it was on a residential street not a highway.

Years ago a member in the 4GS forum had that happen when I had my 4GS, and he immediately traded it in on an LS without that feature. I can sort of understand why LOL

I'm not worried about it, sure it was a fluke but just thought I would share.

 

Thanks for that.

Who knows what caused your PCS to give the false warning? The front obstacle detection on my 2015 ES can give me warnings in certain snow conditions.

 

 

I had similar thing happen to me in both my X6M and M2. Needless to say, I try to remember to shut this pretentious crap off whenever I get in the car.

 

I think it was the transition of roadway surfaces in rapid succession from dark to light to dark to light...

Whereabouts in Annapolis Pat? Maybe I'll give that a try next time I'm out there...

Cant turn it off in the Lexus.

 

No way, there's got to be a way to turn it off. It took me a while to figure out how to turn it off in the M2 - turns out they discretely put two buttons right under where my left knee usually is.

 

 

I have already turned my PCS on my Benz to "late" reaction but I still get false brakes hear and there. In fact, it happened to me two weeks ago. There is this stretch of road where you drive 40-45mph and the road dips downhill and then uphill. At the top of the slight hill, there are two large reflector style "No Left Turn" road signs and some other sign. Im pretty sure that is what triggered the auto braking but it scared me and my passenger *****less. That is one of the only times it has happened without another car in front of me.

 

 

There are a lot of deer in that area. Not likely, but perhaps (?) one was in range of the PCS and you simply didn't see it.....though I'll take your word that you yourself didn't see anything like that, and probably would have noticed the one was there. Patgrim's story, however, about the bridge-abutment near Annapolis is interesting.

Anyhow, that is one reason why I ordered my Lacrosse without that system....I've never trusted it. (I'm with Och on that one)

 

 

Could very well have been the case, lots of construction arrows and reflective barrels around.

I'll have to look...

LOL, no. Had there been a deer in front of me I'd have seen it. It was broad daylight.

 

Is this the bridge you are talking about? It crosses the South River on 450 between Crofton and Annapolis. And, as you say, it goes from dark asphalt to light concrete.

https://www.google.com/maps/@38.9860...7i13312!8i6656

 

 

My car does not have any of the above features, but the IS300 loaner I had last month did and I didn't care for it one bit. There are too many times when making a turn one has to cross over a painted lane line, and then suddenly the steering wheel has a mind of it's own and becomes hard to turn. This can be a hazard when trying to make a faster maneuver, but thankfully I didn't have that come up. I am hoping my next Lexus will have a way to permanently shut off all these nannies. A smart and alert driver can do more good on his/her own, vs. the chances of one of these nannies getting in the way and causing an accident.
Has any studied surfaced showing the rate or % of accidents caused by these? I am sure it does it's share of saving people who are not paying attention, but that aint me and I don't want to carry the burden of irresponsible driver's bad habits.