Speed limiters in cars

[Meerkat]

I live in an area where community speed watch and operation crackdown is a joke

They used to hide behind a hedge on my drive home. It was entertaining to stay in low gear and gun the engine then grin at their disappointed faces as I trundled by at 30.

 

[vinnym70]

Any aspirations around limiters being easy to defeat would be churlish to say the least given the EU has spent time, money and effort to create a policy and enforce it.

Doing 70 in a 50 in a 2022 or later car with a speed limiter fitted but deliberately disabled? Not only would the obvious points for speeding be added to your license but I'd guess a further few points would be added for turning off any speed limiting device (assuming it were something the driver could finagle)

I'm no fan of it but the tech exists now to make it happen. I have no idea where a Tesla that can do 0-60 in 2.5 seconds fits in with this.

 

[87 027]

Doing 70 in a 50 in a 2022 or later car with a speed limiter fitted but deliberately disabled? Not only would the obvious points for speeding be added to your license but I'd guess a further few points would be added for turning off any speed limiting device (assuming it were something the driver could finagle)

I can also foresee a situation where a car's insurance rating includes consideration of the safety features installed and the ease or otherwise with which they can be deactivated. Therefore, if a driver deliberately disables them and is involved in a subsequent accident that could otherwise have been prevented, they could get into a sticky pickle when it comes to claiming against that insurance, quite apart from prosecution for motoring offences.

I have seen newspaper readers write in to grumble about features such as lane keeping assist and asking how they can be turned off permanently. The general advice is don't, as they could affect the insurance cover.

 

[LSWR Cavalier]

Raising the maximum speed limit in motorway road works from 50 to 60 mph (I do not believe it!) is just giving in to crime. I would be quite happy to keep under 50, now I am expected to go faster!

May I claim compensation for increased fuel costs?

 

[AM9]

Personally I wouldn't mind a speed limiter in my car, I live in an area where community speed watch and operation crackdown is a joke. Constantly seeing yellow officers in stupid places like hiding on downhill curves and catching people out when gravity is the primary offender.
Do speed limiters apply the brakes if you go over, ie on a downhill, or are they like class 377s and only stop you accelerating over the limit

I've not heard of an IC engined vehicle using the brakes to control the maximum speed on speed limiters, but my last car had a cruise/speed limiter and on cruise, it would maintain the set speed downhill by using the CVT to apply engine braking. I would expect some EVs to have a fully stabilised speed system as they already have the means to use motor overrun for normal, (i.e. not emergency) braking.
The auto stability control systems on current cars do have limited control of the brakes, but that is to apply differential adjustments to correct steering errors much like retro thrusters on spacecraft.

On the subject of limiting speed, I used to get irritated at some of the community sponsored speed indicators often installed just inside the 30mph limit signs. These signs are OK for reminding drivers that they are in a speed limited area, but some of them are deliberately set low, presumably to try and get traffic to go even further below the legally authorised level for the road. Since I've been able to calibrate my speedometers against GPS I've seen some of them show 30 at speeds as low as 26mph. I don't deliberately speed, especially in built-up areas so now I just ignore them. The only problem now is motorists who not only think that they are official, but also believe that they were speeding and quickly slow down.

 

[Bletchleyite]

Raising the maximum speed limit in motorway road works from 50 to 60 mph (I do not believe it!) is just giving in to crime. I would be quite happy to keep under 50, now I am expected to go faster!

May I claim compensation for increased fuel costs?

Please do some reading on why it was done and why it is safer.

If you do not wish to drive at prevailing motorway speed, there are no journeys that cannot instead be done on A and B roads with a lower prevailing speed.

 

[LSWR Cavalier]

I have done lots of reading and writing about it, published in printed newspapers years ago even.
There are no minimum speed limits!

I used to drive a lot, private and for work, UK and abroad. I would not use A or B roads instead of motorways, that too would be giving in to crime.

I solved the problem for myself by retiring and fixing my life so I need not drive. Highly recommended.

 

[Bletchleyite]

I have done lots of reading and writing about it, published in printed newspapers years ago even.
There are no minimum speed limits!

I used to drive a lot, private and for work, UK and abroad. I would not use A or B roads instead of motorways, that too would be giving in to crime.

I solved the problem for myself by retiring and fixing my life so I need not drive. Highly recommended.

You are aware it is a driving test fault to "fail to make progress" and thus this is considered sub-optimal driving? And minimum speed limits are a thing, though rare - white lettering on a circular blue sign. They often apply in tunnels, e.g. the Mersey Tunnels which I recall have a 30 minimum and a 40 limit though I might remember wrongly the exact numbers.

It is not "giving in to crime" to choose a road that suits your driving preferences. If you don't like doing at least 56mph (lorry speed) when the road is clear, then the motorway is not the place for you.

 

[zwk500]

They often apply in tunnels, e.g. the Mersey Tunnels which I recall have a 30 minimum and a 40 limit though I might remember wrongly the exact numbers.

Including, to great irony, the Blackwall Tunnel, where no doubt the majority of Drivers would be delighted to be able to safely comply with the minimum speed requirement!

 

[miami]

And minimum speed limits are a thing, though rare - white lettering on a circular blue sign.

It worries me how bad drivers who are unaware of basic things like minimum speed limits are allowed on the road.

There should be at least a mandatory theory test every 3 years, for free, online, to keep your license. Would be very low cost to implement, and a minor inconvenience for people to take it. Sure you could get someone else to do it, but the point would be to increase awareness of rules which many people haven't looked at for decades. If 80% of drivers do the test, that is a massive improvement on the current situation.

 

[LSWR Cavalier]

Where are there minimum speed limits? Is failure to comply with them really a problem?
..
As for raising maximum speed limits as mentioned above: do truck drivers now leave decent gaps so one may comfortably use the first lane to join and leave the motorway?

 

[miami]

Where are there minimum speed limits?

Seriously hand in your license. Or at least review your traffic signs.

 

[Bletchleyite]

Where are there minimum speed limits?

Mostly tunnels, though a vehicle on a motorway must legally be capable of 40mph this is a bit different than being required to do so.

Is failure to comply with them really a problem?

Yes, it's an offence as well as being inconsiderate of other road users. I don't know under precisely which law, it may just be Driving Without Due Care and Attention or similar. Obviously if you're required for safety reasons to reduce speed (e.g. because the vehicle in front is going more slowly) that would be a defence.

If you're not happy, in normal conditions, to drive at the minimum speed limit posted for a given road, you should choose not to use that road.

As for raising maximum speed limits as mentioned above: do truck drivers now leave decent gaps so one may comfortably use the first lane to join and leave the motorway?

My experience is that if I accelerate to 56mph (lorry limiter speed) lorries will always let me in, particularly in cases of known short slip-lanes such as it used to be leaving Leicester Forest services southbound. They are generally quite considerate. This is one reason going to 60 in roadworks is an improvement - it could be hard to join if you wouldn't go over the limit to do so. Yes, lorries shouldn't have been speeding, but road safety measures need to be based on what drivers do, not what you want them to do, and cameras aren't generally accurate enough to enforce at 50.00001mph even if you wanted to.

If you aren't comfortable to accelerate to 56mph by the bottom of the slip-lane (or around 70mph if there aren't any lorries and conditions are normal) then the motorway isn't for you as you will be posing an unnecessary risk to other drivers by failing to make progress. If you wish to drive at 50mph or less when the limit is higher, the parallel "regular" road is where you should choose to drive.

If you are trying to join motorways at below the prevailing speed (and I see surprisingly many people doing it*) you are making things hard for yourself and more dangerous. Try it some time, you will find the experience much easier. It's one of those cases where being unduly nervous is self-justifying, because the experience when you're unduly hesitant is so bad, whereas if you aren't then it's easy. If you're genuinely not confident to join a motorway correctly, some motorway driving lessons with a good instructor might pay dividends.

* If I do think someone is going to do that, I tend to hang back on the slip-lane so they get well ahead before accelerating to the prevailing speed myself, so at least I'm not at risk by their actions.

 

[miami]

Yes, it's an offence as well as being inconsiderate of other road users.

In old tunnels (Blackwell + Mersey) especially, the build up of exhaust fumes combined with people staying in the tunnel for a long period of time could well be dangerous

In general as was mentioned upthread (by you?), reasons for failing a driving test include

You should have driven at a speed appropriate for the road and traffic conditions, without holding up other road users.
...

• driving too slow unnecessarily, holding up following traffic
• driving well below the speed limit on clear roads

In 2017, 175 people were injured and two killed in crashes where police believed driving too slowly contributed to the crash.

Crashes caused by drivers going too slow soar by a third

‘Driving like a snail can be as dangerous as driving like a cheetah’.

metro.co.uk

 

[bramling]

Raising the maximum speed limit in motorway road works from 50 to 60 mph (I do not believe it!) is just giving in to crime. I would be quite happy to keep under 50, now I am expected to go faster!

May I claim compensation for increased fuel costs?

The issue is the length of some of the roadworks we see nowadays. 50 mph for 35-40 miles is monotonous, and I think there’s a good case for increasing it.

From a practical level I find 50 mph to be *highly*’dangerous, as it is below the speed limiter setting used by lorries, none of whom seem to observe 50 mph. I’ve found this has led to some extremely dangerous tailgating and/or undertaking, which makes these 50 mph long roadworks an extremely stressful experience to drive through.

So I’m all for 60 mph.

 

[miami]

. 50 mph for 35-40 miles is monotonous, and I think there’s a good case for increasing it.

Isn't 70mph for 35-40 miles equally monotonous?

Since getting a car with a speed limit I find 50mph limits far easier to deal with

undertaking

sit in the lane furthest to the left except when overtaking, how would someone "undertake" you?

If traffic is moving in variable speed queues then stay in your lane. Traffic passing on the left is not "undertaking"

 

[SargeNpton]

From a practical level I find 50 mph to be *highly*’dangerous, as it is below the speed limiter setting used by lorries, none of whom seem to observe 50 mph. I’ve found this has led to some extremely dangerous tailgating and/or undertaking, which makes these 50 mph long roadworks an extremely stressful experience to drive through.

A lorry doing 50mph will be travelling faster than a car doing 50mph. The lorry speed will be based on the more accurate measurement of the tachograph, whereas the car will be based on the over-optimistic reading of the speedo.

 

[bramling]

Isn't 70mph for 35-40 miles equally monotonous?

Since getting a car with a speed limit I find 50mph limits far easier to deal with



sit in the lane furthest to the left except when overtaking, how would someone "undertake" you?

If traffic is moving in variable speed queues then stay in your lane. Traffic passing on the left is not "undertaking"

I can only assume you have never driven through a roadworks attempting to set cruise control to 50 mph.

A lorry doing 50mph will be travelling faster than a car doing 50mph. The lorry speed will be based on the more accurate measurement of the tachograph, whereas the car will be based on the over-optimistic reading of the speedo.

I will generally set the cruise to around 52-53 mph to compensate for this, and it still happens.

 

[Factotum]

Generally they over-read by about 5-10%, so typically if you think you got away with doing 80, you more likely got away with doing 75-76 or so. Pretty sure an indicated 80 on my Kuga is an actual 76 by GPS (I won't say which country I found that out in, for the benefit of the tape ), and an indicated 73 is pretty much dead on 70 (and is what I set my cruise control to through smart motorways as a result).

My Yaris under reads by 3 mph on summer tyres and 2 mph on winter tyres.

A lorry doing 50mph will be travelling faster than a car doing 50mph

Not even Einstein could support that bit of relativity

 

[miami]

I can only assume you have never driven through a roadworks attempting to set cruise control to 50 mph.

Yes I have (well set to what the majority of lorries are travelling at, which is about 49-51 on a GPS). Not a major problem, although some lorries (often foreign registered but I'm not sure if that's just my bias) will go faster and do tailgate, so 60 is better.

I'm happy to do 80 or 90 on an empty motorway, but through roadworks I'm not going to speed.

 

[bramling]

Yes I have (well set to what the majority of lorries are travelling at, which is about 49-51 on a GPS). Not a major problem, although some lorries (often foreign registered but I'm not sure if that's just my bias) will go faster and do tailgate, so 60 is better.

I'm happy to do 80 or 90 on an empty motorway, but through roadworks I'm not going to speed.

Personally I would be comparatively happy to set the cruise to an (actual) 50 mph and let the car do the work. The trouble is, except in the middle of the night it just doesn’t work out like that.

You *will* end up tailgated, undertaken or boxed in. It simply doesn’t work. 60 mph is better. Just have to hope you don’t break down (though in that situation there’s a good case to say it might be safer to try and pull into the cones area).

I find it rather unacceptable the way it is now standard practice to have such long sections of roadworks, nearly always for smart motorway conversion. I might be misremembering but I’m sure there’s been some pushing on 50 miles. There’s certainly ones approaching 40. And they last for 2-3 years too. I know there’s other works which happen at the same time, but 3 years just to convert a hard shoulder is hardly impressive.

 

[miami]

You *will* end up tailgated, undertaken or boxed in. It simply doesn’t work.

On the motorways I drive on the inside lane tends to be full of lorries at the speed limit (on a 50). Sitting at the same speed (maybe 1mph more) as them in the middle lane is fine. Occasionally a lorry will be breathing down your neck, but that's a risk everywhere.

I would agree 60mph is nicer as most lorries have 90kph limiters, but cruise control takes a lot of the stress away from maintaining a given speed

 

[bramling]

On the motorways I drive on the inside lane tends to be full of lorries at the speed limit (on a 50). Sitting at the same speed (maybe 1mph more) as them in the middle lane is fine. Occasionally a lorry will be breathing down your neck, but that's a risk everywhere.

I would agree 60mph is nicer as most lorries have 90kph limiters, but cruise control takes a lot of the stress away from maintaining a given speed

I find it just doesn’t work like that. What happens is the lorries in Lane 1 will inevitably catch up to a car doing well below 50, and will then end up in the middle. If one tries to avoid the lorries by using Lane 3 then sooner or later you’ll be undertaken. It’s a stressful environment which is just waiting for accidents to happen, people too busy getting annoyed over what others are or aren’t doing, and not paying enough attention to their own driving. Likewise too many people not leaving enough of a gap.

 

[miami]

What happens is the lorries in Lane 1 will inevitably catch up to a car doing well below 50,

In that situation I pull out to lane 3 to allow the lane 1 lorry to move to lane 2 (while swearing under my breath at the dangerous lane 1 driver)

But experience varies between people. I don't drive much on motorways. One thing I won't do though is get in lane 1 between a couple of lorries.

 

[AM9]

Yes I have (well set to what the majority of lorries are travelling at, which is about 49-51 on a GPS). Not a major problem, although some lorries (often foreign registered but I'm not sure if that's just my bias) will go faster and do tailgate, so 60 is better.

I'm happy to do 80 or 90 on an empty motorway, but through roadworks I'm not going to speed.

The conversation on this thread really is getting bizarre with people who adhere to the speed limit being blamed for accidents caused by others breaking the speed limit. Everybody has control of the speed of their own vehicle, so there is no 'excuse' for speeding. The highway code rightly says:

You should drive at a speed appropriate for the road and traffic conditions, without holding up other road users.

driving too slow unnecessarily, holding up following traffic​

​

driving well below the speed limit on clear roads​

The critical word is appropriate which with different road and traffic conditions will be interpreted differently by individual drivers. Just because some want to drive at the maximum limit doesn't make that safe, - there are many situations where there is a vast difference between vehicle speeds, e.g.:

in foggy conditions - far too many drive on the car in front's rear lights leading to multiple vehicle collisions​

in icy conditions - patches of ice, - especially black ice which is not easy to see at speed​

heavy rain particularly when there is spray just like fog but with additional problemds of aquaplaning​

poor visibility through low sun, very difficult to see but only lasts a few minutes at most​

So many drivers proceed on the edge of their ability that any unexpected move by another driver results in major incidents.

 

[Bletchleyite]

My Yaris under reads by 3 mph on summer tyres and 2 mph on winter tyres.

Do you actually mean under-reads, e.g. showing 40mph if doing 43? If so it is not roadworthy and so needs calibrating or replacing. (The chance of being caught is fairly low but I'm pretty sure it is a Construction and Use offence).

Over-reading, e.g. showing 43 if doing 40, is very common to avoid this.

 

[Meerkat]

Yes, lorries shouldn't have been speeding

Are they speeding or do they just have more accurate speedos?

If you are trying to join motorways at below the prevailing speed (and I see surprisingly many people doing it*)

Far too many do it, and it’s incredibly dangerous - especially the ones who only look for a gap when they get to the line and then stop at the end of the slip road!
Rather than just chasing speeding they should put cameras on the slip roads and make some of these muppets retake their tests - they clearly aren’t up to standard.

 

[ABB125]

Are they speeding or do they just have more accurate speedos?

Probably a combination of both. Supposedly foreign lorries can get away with speeding through 50mph limits on motorways because there's no way to fine them (I don't know how accurate that claim is though).

Incidentally, I can drive at an indicated 60mph on a single carriageway, and be travelling at the same speed as the lorry in front. Clearly something about this situation is a bit dodgy...

 

[miami]

The problem with speeding is it's easy to measure, automate and prosecute, especially cars (it's harder to trigger a camera specifically for a hgv so limits are set to the maximum (car/bike) limit, and nobody enforces vans doing 65mph on a dual carriageway, or lorries doing 50 up a single carriageway).

Bad driving (which could well be a car doing 60mph in terrible visibility up a 70mph dual carriageway) is far more problematic and costly to enforce and prosecyte, so we don't bother.

Ultimately over twice as many people are killed and seriously injured when the speed limit is 20mph (or below) than on a motorway -- 1970 vs 894 in 2019. Another 14,000 on 21-30mph roads and 2,500 on 40mph roads.

Motorways really are the safest roads.

 

[A0wen]

The sooner humans are no longer in control of vehicles, the better!

Nice try - but somebody has to programme a computer. So all you're doing is moving *which* human controls the vehicle and I'm not sure I'd trust the Musk-rat or the likes of Apple with that.