20mph limits unenforceable?

[Randy Butternubs]

Hi all. I recently went on a (motor) Bikesafe course run by the police. It was rather good and I recommend those of you with motorbikes to check it out. One of the officers said a couple of things I hadn't heard before which I thought were pretty significant.

There's been a lot of talk about 20 limits - they they're great and we should have more of them, or that they are useless in practice as they are rarely enforced. Or even that it's been publicly announced that a new 20 limit will not be enforced.
What I hadn't heard is that 20mph limits are legally impossible to enforce. Apparently car speedometers are only legally required to be accurate over 30mph. For this reason speed cameras in 20mph limits are set to trigger at 36mph as they are for 30mph limits. Given that most speedometers read optimistically to help prevent drivers from getting into trouble you would likely need to be traveling at an indicated 40mph to set off the camera!

The other thing he said was that, as of last week, red light cameras will now be triggered by (motor vehicle) ASL violations. This seems rather harsh to me as the penalty is apparently the same as if you jumped a light - 3 points and a (£60?) fine. It would be nice if it stopped people parking in them though.

I would be interested to know if anyone has heard anything about the above points and can confim/deny. Please weigh in with opinions too

 

[StuartG]

The study on the original London's 20 mph zones concluded that the real reduction in average speeds of around 10 mph was not due to enforcement (there wasn't any) but by calming measures. I had always thought that was the only way.

Until a couple of weeks ago I had to go all around Islington by car (don't ask). Lots of banners proclaiming it as the first 100% 20mph borough and the traffic was mostly respecting it despite no calming. Quite a surprise.

Of course there was the odd boy racer. But nothing will stop those guys short of a zap gun.

 

[anyuser]

The other thing he said was that, as of last week, red light cameras will now be triggered by (motor vehicle) ASL violations. This seems rather harsh to me as the penalty is apparently the same as if you jumped a light - 3 points and a (£60?) fine. It would be nice if it stopped people parking in them though.

I would be interested to know if anyone has heard anything about the above points and can confim/deny. Please weigh in with opinions too

I would be surprised if this was the case. Wouldn't they have to move the inductive loops/strips at all the junctions back to the first stop line?

 

[Randy Butternubs]

@ StuartG - You're right. I didn't mean to overstate the importance of enforced limits in reducing speed. I was also under the impression that traffic calming measures were necessary - it's a shame that the go to method seems to be bloody speed-bumps .

@ anyuser - Are you sure the cameras trigger from the induction loops? I assumed they used motion sensors like speed cameras(?)

 

[Davidc]

The red light cameras on a junction near here use motion sensors and operate if the lights are at single colour red. The only oddity if they're going to do ASL as well is that bikes set them off (i.e. make them flash)

I don't see enforcing ASLs as harsh, any more than enforcing any other aspect of traffic law. As I've often commented before, my view is that traffic offence penalties are very light so there's no grounds for complaint.

(My preferred penalty for RLJ would be a fixed £5000 fine and 12 months ban - and that's first offence. Cyclists would get the same but without the ban, speeding and drink drive would be at least double that. I have to drive 25,000 miles a year and want some protection, I ride a bike and the same applies.)

 

[glasgowcyclist]

What I hadn't heard is that 20mph limits are legally impossible to enforce. Apparently car speedometers are only legally required to be accurate over 30mph.

Regulation 35 Road Vehicles (Construction and Use) Regulations 1986 states that every motor vehicle shall be fitted with a speedometer except:
•a vehicle having a maximum speed not exceeding 25 m.p.h.,
•a vehicle which, at all times, is unlawful to drive at more than 25 m.p.h.,
•an agricultural motor vehicle driven at not more than 20 m.p.h.,
•a motor cycle not exceeding 100cc first used before 1st April 1984,
•an invalid carriage first used before 1st April 1984,
•a works truck first used before 1st April 1984,
•any vehicle first used before 1st October 1937,
•a vehicle fitted with an approved tachograph which is required or not.

Vehicles first used on or after 1st April 1984 the speedometer should be capable of indicating the speed in miles per hour and kilometres per hour. Vehicles may instead comply with EC Regulation (Community Directive) 97/39 or ECE Reg 39.
These directives stipulate the markings, graduations of the speedometer and refer to 75/443/EEC which specifies the tolerances.
The indicated speed must never be less than the true speed (it must read exact or high) and between 40km/h and 120km/h the error must not exceed 10% + 2.5 m.p.h. high (true speed/10 + 4kph).
This means at a true speed of 25mph or 40km/h the speedometer may read 40/10+4 = 8km/h or 5mph high = 30mph indicated.

My reading of the accuracy requirement above is that in all circumstances the speedometer must not show less than the true speed and in addition, where the speed is between the limts specified, the error level must not exceed 10% plus 2.5mph.

I think someone has misunderstood that to mean that there is no requirement for speedos to be accurate below 25mph. In my view that's wrong so I don't see why someone couldn't be prosecuted for exceeding a 20mph limit.

GC

 

[anyuser]

@ StuartG - You're right. I didn't mean to overstate the importance of enforced limits in reducing speed. I was also under the impression that traffic calming measures were necessary - it's a shame that the go to method seems to be bloody speed-bumps .

@ anyuser - Are you sure the cameras trigger from the induction loops? I assumed they used motion sensors like speed cameras(?)

I was going by this page
http://www.wmsafetycameras.co.uk/cameras_work.php?cameramovie=RedLight
They definitely say sensors 'in' the road which would be inductive I think. But I am open to being corrected

 

[Dan B]

.
What I hadn't heard is that 20mph limits are legally impossible to enforce. Apparently car speedometers are only legally required to be accurate over 30mph.

Why should that make the limit unenforceable? You can be done for drink driving despite there being no legal requirement to carry a breath alcohol tester at all.

 

[Mile195]

I couldn't confirm or deny whether or not they're enforceable. I do think they're a complete gimmick though. They exist mostly on back streets where you can't set speed traps anyway.

IMO all they've done by sticking them everywhere is make people used to seeing them, so now people don't take any notice of any of them.

I remember when I very first came across 20mph limits, because they were a rarity I assumed that there must be something important that warranted it, like a primary school or an accident blackspot, and you monitor your speed more closely as a result. I don't get the same impact now they're on every single side road - the signs have just become yet another ugly piece of road furniture.

I agree that traffic calming is more effective though. Well, when properly placed.

 

[snailracer]

AFAIK 20 mph limits are legally enforceable, it's just that most police forces decided they wouldn't because they got no extra funding to do so.

 

[neil_merseyside]

AFAIK 20 mph limits are legally enforceable, it's just that most police forces decided they wouldn't because they got no extra funding to do so.

I attend the odd cycle forum and indeed have heard that our (Wirral/Merseyside) police state that they will not regularly enforce the 20mph 'due to likely workload' (or some such wording) BUT that high profile occasional driving advice awareness teams would operate (using CPSO and volunteer residents etc) to 'flag' the change.

However most councillors/experts seemed confident that enough drivers would be decent and slow down, and as such would essentially cause compliance of others, as our 20 zones are all residential then most people actually seem happy to comply (local with kids?) and as none of the larger feeder roads are posted down from 30 then the 20 only affects the last few hundred yards of most peoples journey!

Obey/compliance in this context is 'the majority' at or about 'x speed' +y% error (over obv. !), so speed reduces by most of the reduction...

 

[morrisman]

The 20mph limit over Tower Bridge is enforced by average speed cameras.

 

[deptfordmarmoset]

Hmm, a little thought from the back streets of London: does using bumps to slow down vehicles with suspension and inconvenience cyclists (usually without suspension) really make good sense? And hands up if you've ever been forced out of your lane because there's a 4x4 driving head on at you in the middle of the road? To avoid those bumps...

 

[Dan B]

Hmm, a little thought from the back streets of London: does using bumps to slow down vehicles with suspension and inconvenience cyclists (usually without suspension) really make good sense?

I habitually ride over speed bumps on a bike with no suspension at speeds greater than most car drivers will attempt. YMMV if you have dodgy knees or a large unsprung load that won't enjoy it (e.g. child in a bike seat) or maybe if you're on a recumbent and can't honk

 

[dellzeqq]

Why should that make the limit unenforceable? You can be done for drink driving despite there being no legal requirement to carry a breath alcohol tester at all.

quite.

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