Acc (Adaptive Cruise Control), Is It Any Good?

Ian Milner · January 22, 2012

Will be buying a 450h in the nearish future (hope to pick up one that's been traded it when the new GS is launched).

One thing on my must have list is the ACC system. I'm a great fan of cruise control, and use it most of the time, especially in 30s, 40s and 50s to make sure I don't speed.

My question is how 'intelligent' is the ACC? for example:-

If you're on the motorway, does the radar ever think a car you're overtaking is actually in front of you and applies the brakes or slows down?
If you're following traffic on a normal road, does the radar ever 'lose' the car your following as you go through bends, causing the car to accelerate to the pre-set speed as it thinks the car has disappeared, only to suddenly brake when it 'sees' the car again on the next straight?
Also, I've heard that the ACC only operates at speeds of 30mph or above is this true? If that's the case, what happens if you approach a 30 zone and reduce the set speed to 30 and then come up behind something going slower. Does that car slow itself, or do you have to brake or press cancel (like a standard cruise control system)?

Hope someone out there is also a cruise fan and can answer my question.

Cheers, Ian.

The Swede · January 22, 2012

Ian, I have this on my Merc S63 and it's a great thing. Never though I'd actually be using it this much.

It takes getting used to, but in commuting traffic on the motorway, especially on the M25 for instance, it's really practical: the car just follows the one in front and stops and accelerates as he does.

The Merc system works at any speed upto 150mph. I only use it upto 90 ish, afterwards, I wanna be boss myself.

Bends are no problem, don't worry, it takes the steering angle in account.

Overtaking a car is also not a problem, unless you try getting too close before changing lanes. Otherwise, on a motorway, it only looks at whether the guy in the other lane (which you are overtaking) is moving towards your lane. If he doesn't, it keeps going. If he does (risk of him pulling out in front), it slows down.

All in all, it's much more intelligent than I thougt and I'd take it as option any time again.

tonyricha · January 23, 2012

It is completely wizzard, makes me feel SO safe on the motorways but you do get mugged by people pushing into what the car considers a safe gap to follow, range is selectable so no real issues but you must think ahead because we all drive by predicting each other but the car can only react to a situation.

They say dont use it in fog but I disagree, if it can "see" further than I can why not trust it?

The only time mine catches me out is on a long right hand curve on a dual carriagway it sometimes thinks the vehicle we are about to pass is a collission risk and brakes but you soon learn what is is likley to do.

If your speed drops below about 26MPH the cruise control system shuts down so the car will freewheel.

Another slight issue is if the auto wipers kick into high speed (HGV spray) it will abort the cruise control but again freewheel

I did recently ask a bunch of traffic patrol officers what would happen if the car braked hard and I was hit from behind could I be responsible thru being "not in control of my vehicle" they were adamant saying No as the system is approved for use in the EU

Go buy it! Tony

PS The wifes Sportcross has normal cruise so I keep waiting for it to brake for me, now that is dangerous !

Ian Milner · January 24, 2012

Thanks Tony, that's exactly the detail I was after. It's a definite YES and as all pre-facelift SE-L grade had it as standard (according to a 2007 brochure I recently bought) then I'll be looking at a 57 plate car (unless I find an 08 with ACC and reasonable mileage in budget).

Just need to lose weight now! Started at 92.9kg, now at 89.4kg after 15 days so only another 60 days to get to 75kg.....

MrShades · January 26, 2012

Thanks Tony, that's exactly the detail I was after. It's a definite YES and as all pre-facelift SE-L grade had it as standard (according to a 2007 brochure I recently bought) then I'll be looking at a 57 plate car (unless I find an 08 with ACC and reasonable mileage in budget).

Just need to lose weight now! Started at 92.9kg, now at 89.4kg after 15 days so only another 60 days to get to 75kg.....

I think you might be wrong with the assumption that any pre-facelift SE-L has ACC/PCS.

I'm pretty sure that when I was looking for my 450h (and also had ACC/PCS as an essential option) I went through MANY potential SE-L spec cars that didn't have it.

If an SE-L spec car has a sunroof then I'm pretty certain it also has ACC/PCS (they were linked options) - but the only real way to check is to look for the 'distance control' button on the right hand side of the steering wheel. There's a post on here somewhere about it, that I replied to with steering wheel photos showing the difference between ACC equipped and non-ACC.

Good luck in your hunt - the 450h is a great car, and ACC is a fantastic option that really makes cruise control usable in the UK, even on a busy motorway or A road.

Shades

Ian Milner · January 26, 2012

Thanks Shades.

I'm thinking it was standard on SE-L because the brochure I have (from Jan 07) shows it as standard on SE-L and option on SE and Sport. Whereas a brochure from 08 of the facelift model says it's an option across all grades (and linked to sunroof option).

I'm aware of the switch on the wheel as being the tell-tale sign of the ACC but unfortunately many pictures on auto trader and Lexus dealer websites don't show a straight on photo of the steering wheel, and it's often just described as cruise control instead of adaptive cruise control, or the PCS isn't mentioned. What I find frustrating is the fact that even Lexus don't make it clear in their own adverts of approved used cars!