Cruise Control & Speed Limiter thoughts

August 30, 2018

On a slightly different tack to the topic "Radar cruise control query - don't do this at home!" since getting my Gen 4 Prius I've found the Speed Limiter incredibly useful in situations where the Adaptive (aka Radar) Cruise Control is either inappropriate (due to congested area, bendy roads etc.) or below the 28 mph minimum setting speed.

I've often wondered why the cruise control can't be set below a certain speed (28 mph for Gen 4 Adaptive, 26 mph on the 'ordinary' CC on earlier models of Prius and 22 mph on a Volvo I owned in the 1990s), especially on automatics and more so for CVTs like the Hybrids. I know the Adaptive variety will follow cars below this speed and keep a set distance, but if there's no car in front, or the car in front is speeding, that's no help. It would be SO useful in some of the long, straight 20 mph zones I frequently encounter to set a target speed of 20. 10 & 15 mph would be useful on some private estates and Royal Parks (once when doing some volunteer work I was rapped over the knuckles by Royal Park Security for doing 12 mph in a 10 limit!).
That said, the speed limiter can only be set at 20 mph or above. WHY???
and why did it take Toyota so long to offer a Speed Limiter feature?

But a major shock came last week was when I was tempted by a Lexus RX in a spec that was really tempting on the forecourt of my dealer when I went for my 30k service. It was 10 months old, 5½k miles, about £9-10k below new price. F-Sport spec, so great digital speedo with user selectable tachometer/HSI and adaptive dampers, Premier option, so HUD (including SatNav info), 10 way electric memory seats and lots of other goodies.

BUT, a show stopper! No Speed Limiter. I couldn't believe a 66 plate Lexus of this price range didn't have this when some Aygos do! I downloaded the handbook, and sure enough, no mention, not listed in the warning lights page, and no sign of the button on the steering wheel. Having had this for just over 2 years and 30,000 miles, it's now on my list of must haves.

August 30, 2018

That does seem strange especially on a car of that spec and a car which I assume is based on the Prius hybrid. I see in the 2017 brochure it says "All speed dynamic radar cruise control" so maybe being able to set it for all (any) speed, you can set it for 5-10-20 mph and it will keep that speed unless a car is detected in front of you going slower than 10mph. Would that be the same as using a speed limiter? I confess, I've not used the speed limiter on my Prius, will have to give it a go...

August 30, 2018

You will find the same description of the UK Prius ACC in some places, it just means it will control the speed down to 0 mph if the car in front slows to a low speed or stops.

The Prius manual has 3 sections:

Dynamic radar cruise control with full-speed range...............................336
Dynamic radar cruise control.............................351
Cruise control....................365

The manual says it can be activated "above approximately 50 km/h [30 mph])", but in practice it will accept 28.

The speed limiter prevents the speed rising above the set speed, so if set to 20, it will accelerate quite briskly to that speed, then go no faster, even if the accelerator is nearly to the floor. For emergency situations, you can floor the pedal hard to quickly override this (or pull the CC stalk to cancel it. It uses the same stalk as the CC, and a single flick will increase/decrease set speed by 1 mph, holding increments by 5 mph.

Lexus models were the first cars I drove with Adaptive Cruise Control (some 7-9 years ago when I got lent the occasional LS or RX for a day or two) and I'd wanted a car with it ever since. This was a key factor in my trading a perfectly good Gen 3 Prius with ordinary CC for my current Gen 4.

Those Lexus models also would follow cars down to zero mph, but the set speed also had to be above about 28 mph.

One neat touch on the LS & RX, was on the screen display, little brake lights lit up on the picture of the car when it put the brakes on. I wish the Prius did this, as sometimes when it's slwoing I'd like to be sure I'm showing my brake lights to following traffic, but can't be sure when they come on so sometimes find myslef braking just to show the lights, which of course cancels the CC.