Adaptive Speed Limiters | 80mph on the Motorway!?

Time to have a look at some new car tech in my loaned Audi Q4 e-tron! Do you know what an adaptive limiter is or how it works?

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[Feeshgmod]

I reckon its set to 80 so that if youre on the on ramp on a motorway you have a bit of flexibility if you needed to speed up for some reason, not that you should go over the speed limit to do that

[jonnycraig]

My wife had a car that use to read the road signs and it once read the km/h sign on back of a bus while on the motorway and put up 120 as the speed (which made us laugh)

[SamBebbington]

The balls to say: “Have I committed an offence there? Yes, legally I have”

Great video Ashley!

[pangolin]

Don't worry about committing any offences Ashley, the police in this country have said that they don't investigate retrospective crimes

[jasonk]

The case for buying a car without all these electronics and touchscreens, looking after it and keeping it for as long as possible gets greater by the day.

[studiosoftmorecambe]

We are breaking the law if we use a mobile phone whilst driving yet the law makes no mention of fiddling with all the distracting gizmos that are fitted as standard in most new cars these days. Many drivers are unable to concentrate on the basics of driving without all the distractions.

[rgtlm]

I got a 17 year old car with no speed limit, no lane assist, no parking sensors, just the purest form of driving and I wouldnt want it any other way

[andrewhill]

Adding another level of complexity to the complex task of driving which is for some people is already beyond their ability! Excellent video, not scared of pointing out the limitations. Every man needs to know the limitations of his car (and himself!)

[retroonhisbikes]

As all things government they’ve got it wrong.
Anti tailgating devices with auto braking would be a far better approach to road safety.
Travelling on the motor ways i see gaps of 1 or 2 car lengths in groups of 4 to 5 cars, by the time car 5 has noticed car one has stopped he is already in the boot of car 30/40.
Driving at 80 in fog that’s clever.

[MK-]

What an interesting video - "we have to embrace technology but we can't rely on it" is a great line.
What will motorways be like in future if most cars are limited to 70 - will it encourage a more relaxed style of driving?

[Daye]

That's why I like adaptive cruise control more. As soon as you touch the accelerator or brake, you start overriding it.

[stuartjohnston]

Like you say, not a perfect system. I've noticed problems where lower speed limit roads, cross via bridge, a higher limit road. For a moment the system thinks the limit has vastly reduced and tries to slow down sharply. Can also happen where a lower limit road is parallel to a higher limit. Also, for myself, lane keep assist does not work on our local roads. Many potholes and poor drainage means you are constantly fighting the system to preserve your tires, wheels and suspension. We have it permanently switched off in the wife's new corsa.

[redtela]

Counter point on the limiter detecting 80 on the slip-road... as we all know, lots of traffic on the motorway exceeds 70mph. I speculate that the manufacturers are aware of this, and designed the system to allow you to get going up the slip road & merge safely, then backing the limit down to 70 after you've merged.
Rather than a fault, this is a system design choice - same as it making you slow down after the 50 sign... the car might not know that it's not safe to slow down before the sign (eg, someone close behind on the rear). The interesting question for me, is when it forces you to slow down, does it show brake lights?

[petercotton]

Impressive technology that will save lives in the future.

[Rdrunner]

Fascinating film, Ashley. Good to see things working (or not working!) in practice.

You asked about the setup on our cars. My car does have an optional speed limiter function and it separately also has a speed limit adviser function which shows a visual indication of what the GPS and/or sign reader thinks is the national speed limit. It is usually right, but sometimes gets it wrong. For example:

(1) There is a school nearby on a main 40 mph road where there is a part time 20 mph speed limit but only when the lights flash. Without fail, the system read the sign and thinks the speed limit drops to 20 mph regardless of whether or not the lights are flashing. If I had an adaptive speed limiter linked to the car, it would slow down to 20 mph. I would be obstructing traffic and / or could have somebody crashing into the back of me.

(2) A road near me is a 60 mph limit up a steep hill but the speed limit signs are posted right at the junction coming out of a 40 mph sign. As a result, the speed limit adviser thinks the limit is only 40 mph... then after a mile it gives up and displays dashes "- - -". If there was an adaptive speed limiter linked to the adviser, I have no idea how it would cope with that.

(3) I have driven down a 40 mph speed limit where the adviser thought the limit was 60 mph. No idea why.

You also asked about what use we make of speed limiters. I generally don't use the speed limiter. One problem is, if I want to override the speed limiter (for example, when joining a motorway with traffic behind where I need to push on to a gap in lane 1 and can't really slow down without making life very dangerous for the drivers behind me) then I would need to go "pedal to the metal". At that point, the gearbox drops two cogs and the supercharger kicks in, resulting in a sudden jerk of excessive acceleration that can even cause the back tyres to scrabble for grip. Not good. I prefer to use personal judgement for keeping to the speed limits and to use acceleration sense to make my throttle inputs smooth when needed.

Also the speed limiter only works on the throttle, so if I am going downhill the car will actually exceed the speed limit unless I am watchful and drop a gear or use the brakes. On hybrid or electric cars, that's not such an issue: the car simply uses regenerative braking to keep the speed at the target and also charge up the battery pack.

In conclusion: I have dabbled with the speed limiter, encountered the above problems and decided only to use it sparingly. YMMV.

[ryboxer]

So this interuptive device that is not ready yet is going to become law before it works properly, this along with 'lane keep assist' are as safe as smart motorways!

[waerlogauk]

Where there is an urban road (30mph) parallel to a motorway I often find the GPS gets the wrong road. Currently, this only messes with the navigation but the speed limiter could also be set incorrectly, either high or low.

[ace_]

Every car I’ve had with a limiter fitted (although none that have automatic speed adjustment) all have the ability to be overridden by a decisive prod of the throttle. The traffic sign recognition software, which the limiter would use, isn’t perfect though. I’ve had my car reading the signs from adjacent roads, missing signs entirely and even reading the signs of the back of lorry trailers. Nothing beats being observant and not relying on these flawed systems.

[TheGrinningSkull]

10:26 “because they want to queue for longer”, hilarious!

[PPT]

If we get the option to turn this system off, I will do it every single time I get in the car, the same way I always disable the "lane keeping assist" feature and the adaptive cruise control.
- Lane keeping assist pushes you towards danger sometimes. If it doesn't like the line I'm taking through a turn, it will push me in the wrong direction and then I have to correct it. Unsettling the car like this on a rainy day is pretty scary.
- Adaptive cruise control : Slams on the brakes when someone cuts in front of me to make a late exit. Also, if the car in front is constanly changing speeds, your car will do the same instead of keeping to an average speed...
- Automatic speed limit : I cannot be bothered to deal with the system misreading a situation and wrongfullt slow the car down. My driving is all about planning, if the car starts throwing surprises at me, I'm going to get pretty annoyed.

The only "new" feature I find usefull is the the emergency braking, I believe it can really make a difference, but it also has its limitation and I have ended up stopping in the middle of the road for no reason once or twice.
I never had a speeding ticket and I never rear-ended anyone, all it takes is to pay attention. When you're driving, you're driving and that's it.