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Croydon-wide 20mph road traffic speed limit

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grid56126

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In fact, I'm a road that - sort of - has a 20mph limit.

It's quite simple, are there circular signs with red edging around a "20". If there are it is 20 (compulsory and enforceable) if there are not, then it is not. There can be no "sort of"
 
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jon0844

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While you can have different speed limits in two directions, as far as I am aware the carriageways must be separated. I think it required a specific change in law to work, and as such only works on dual carriageways. There's only two roads I can think of, and one of these is the A10 between Waltham Cross and Cheshunt (College Road). 40mph one way, 70mph the other. It always used to be 70 in both directions.

How can you enforce a limit where the same road has two different speeds depending on which road you used to enter? And if you park up, then leave the next morning, which limit is it then? Still the one from the last entry point? And if you always come in from the other end where it's 30mph, can you be done?

I think you'll find there has to be a traffic order and whatever else is required to impose a different limit beyond the normal 30mph in town. Otherwise any local resident could get a sign made up and place it on a post, then expect people to be prosecuted.
 

Haydn1971

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A local speed limit order is required whenever the speed is different to the "national speed limit" that being 70mph on unlit duals, 60mph on unlit single carriageway or 30mph on any road with a system of street lighting. You do not need repeater signs on roads that are "national speed limit", this term should be confused with the usual lay term of national speed limit - i.e. the white roundel with black diagonal stripe. There are also added complications such as special roads, motorways, vehicle class limits and such.
 
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AM9

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While you can have different speed limits in two directions, as far as I am aware the carriageways must be separated. I think it required a specific change in law to work, and as such only works on dual carriageways. There's only two roads I can think of, and one of these is the A10 between Waltham Cross and Cheshunt (College Road). 40mph one way, 70mph the other. It always used to be 70 in both directions.

How can you enforce a limit where the same road has two different speeds depending on which road you used to enter? And if you park up, then leave the next morning, which limit is it then? Still the one from the last entry point? And if you always come in from the other end where it's 30mph, can you be done?

I think you'll find there has to be a traffic order and whatever else is required to impose a different limit beyond the normal 30mph in town. Otherwise any local resident could get a sign made up and place it on a post, then expect people to be prosecuted.

I've always thought that there is another issue with 20mph signage. We are all used to 30mph by the existence of signs at the entry to the area and the constant reminder that if there are street lights not more that 200m apart (can't remember the exact distance), and unless other signs dictate to the contrary, the default limit is also 30mph.
Once in a 20mph, there are not always repeaters to remind drivers that the limit isn't 30mph, so are drivers expected to remember that the area has the lower limit? It could be overnight, or even a car could have been delivered by a hire company. Are they then duty-bound to inform the driver of the speed limit? It would be an interesting court case if a driver said that he/she had not been informed of the speed limit and assume in accordance with the Highway Code that a 30mph limit prevails especially if a RTA was involved?
 

Haydn1971

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AM9 - you are thinking of a 20mph Zone, which is a variation on a theme, in that the speeds are self regulated by traffic calming features - no part of a zone should be more than 50m from a calming feature and a cul-de-sac should be no longer than 80m from a feature - rules have been relaxed recently on what constitutes a traffic calming feature. Typically hump frequencies in a 20mph Zone range between 60-80m apart to regulate speeds at about 24-26mph
 

Bletchleyite

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Once in a 20mph, there are not always repeaters to remind drivers that the limit isn't 30mph, so are drivers expected to remember that the area has the lower limit?

Unless in a "20mph Zone", which must have extensive traffic calming to keep the speed down, there legally have to be. But as you are travelling quite slowly it may feel like they are very spaced out.
 

AM9

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AM9 - you are thinking of a 20mph Zone, which is a variation on a theme, in that the speeds are self regulated by traffic calming features - no part of a zone should be more than 50m from a calming feature and a cul-de-sac should be no longer than 80m from a feature - rules have been relaxed recently on what constitutes a traffic calming feature. Typically hump frequencies in a 20mph Zone range between 60-80m apart to regulate speeds at about 24-26mph

OK, take St Albans' main thoroughfare, St Peters Street/Chequers Street. It is 20mph throughout and has very subtle raised tables at pedestrian lights only. As far as I can remember, it only has signage at the ends of the route which includes a mini roundabout.
There is often a queue from end to end especially during peak/school pick-up hours and on market days. There are however many times where one can and some do go well above 20mph between the roundabout and the signalled 'T' junction at Victoria Street. In the evenings, the speeds increase most of the time but AFAIK, the limit still applies. There is a Premier Lodge hotel within the area and it would be possible to change drivers there or some other places.
So, without a visible sign or real traffic calming measures, a driver starting their journey within the area would assume that the limit is 30mph. The ACPO recommendations for prosecuting speeding gives 2mph + 10% leeway for all speed limits above 30mph, but specifically mentions 20mph as an absolute maximum with no allowance for driver/car measurement uncertainty.
What would a court do with such a case where an injury or damage occurred?
 
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jon0844

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Variable speed limits would make more sense. During rush hour, school hours or whatever, it's 20mph. At other times, it's 30mph. Either with signs that state times or, better still, electronic signs that change.

On major roads, not side roads or residential estates.
 

Bletchleyite

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Variable speed limits would make more sense. During rush hour, school hours or whatever, it's 20mph. At other times, it's 30mph. Either with signs that state times or, better still, electronic signs that change.

On major roads, not side roads or residential estates.

You do get those, and technology makes them ever easier.
 

jon0844

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Yeah, but we don't have the technology used anywhere near enough. It could make a huge difference on loads of roads, but it's obviously cheaper to just go for the lowest limit which patronises safe drivers who are now made to do 20/30/40 even at 2am, because of the genuine need to reduce speeds at certain times.

As said above, it just makes people ignore the limits and once that happens, you're asking for trouble.
 

ainsworth74

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Variable speed limits would make more sense. During rush hour, school hours or whatever, it's 20mph. At other times, it's 30mph. Either with signs that state times or, better still, electronic signs that change.

Those would be useful in other areas as well and I hope they got rolled out soon on a wide scale. For example where I live the A66 which runs through Middlesbrough and is a major east/west link for Teesside and is a two lane dual carriage way. It has a blanket 50mph limit until your beyond Stockton. During the rush hour it's neccessary because of the volume of traffic trying to join and leave at various junctions. But otherwise during the day and overnight it could easily be 70mph with no real impact on safety.

Hopefully the deployment of electronic variable speed limit signs will mean that roads like this can have their speeds better tailored to traffic flow.
 

jon0844

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Motorways seem to do well with variable limits, so it's really just the cost that is likely holding back a wider roll out. I assume there's also the issue of what happens if digital signs fail. There clearly needs to be a 'fail safe' and how would that work? Everyone knows that you revert back to nn mph if there's no sign displayed?
 

Bletchleyite

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Motorways seem to do well with variable limits, so it's really just the cost that is likely holding back a wider roll out. I assume there's also the issue of what happens if digital signs fail. There clearly needs to be a 'fail safe' and how would that work? Everyone knows that you revert back to nn mph if there's no sign displayed?

The way the motorway ones work is quite clever - I understand there is a fibre optic connection between the limit display and the camera, so what is *actually* displaying appears on the photo. If the limit was not displaying per the law, there would not be a case.
 

Haydn1971

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What would a court do with such a case where an injury or damage occurred?


Lots of factors here, but ultimately, ignorance of the speed limit is no defence in the eyes of the law - assuming the order is correct of course ;)
 

Busaholic

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So, without a visible sign or real traffic calming measures, a driver starting their journey within the area would assume that the limit is 30mph. The ACPO recommendations for prosecuting speeding gives 2mph + 10% leeway for all speed limits above 30mph, but specifically mentions 20mph as an absolute maximum with no allowance for driver/car measurement uncertainty.
What would a court do with such a case where an injury or damage occurred?

I'm unsure which ACPO guidelines you're quoting from. What I believe to be the current version dated 14th October 2013 and valid through to review in May 2015 certainly quotes the 2 mph speed device tolerance at 20 mph and indicates that a speed of 24 to 31 mph would be appropriate for the offender to be offered a place on a speed awareness course - over 35 mph would result in prosecution with points/possible disqualification if found guilty. 24 mph is, in effect, 20 mph plus 2 mph plus 10%. The document was written by Suzette Davenport, Chief Constable lead on traffic policing.
 

AM9

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I'm unsure which ACPO guidelines you're quoting from. What I believe to be the current version dated 14th October 2013 and valid through to review in May 2015 certainly quotes the 2 mph speed device tolerance at 20 mph and indicates that a speed of 24 to 31 mph would be appropriate for the offender to be offered a place on a speed awareness course - over 35 mph would result in prosecution with points/possible disqualification if found guilty. 24 mph is, in effect, 20 mph plus 2 mph plus 10%. The document was written by Suzette Davenport, Chief Constable lead on traffic policing.

OK I stand corrected on that. The one and only speed ticket that I have received (69 in a 60 limit) in 2006 had details about the then ACPO recommendations. They said that 30-70 limits had the usual 2mph+10% tolerance that wouldn't normally be subject to action but with 20mph, there was no grace and any speed recorded above 20mph may result in action. Maybe it has changed since.
 

radamfi

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It has a blanket 50mph limit until your beyond Stockton. During the rush hour it's neccessary because of the volume of traffic trying to join and leave at various junctions. But otherwise during the day and overnight it could easily be 70mph with no real impact on safety.

Lower limits on fast roads through urban areas are also used to reduce noise and pollution. When planning new roads, it helps the environmental appraisal as part of the justification of the scheme.
 

ScotGG

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I've been scouring the internet for something definitive, unambiguous and, most of all, correct, but it's pretty hard to find. The best I can find is from ACPO (the Association of Chief Police Officers) which states 20 mph limits are legally enforceable then goes on to indicate that, in normal circumstances, the police have better uses of their time than to do this! There is a hint, too, that a 20mph limit that is not part of a 20mph zone might just attract more police attention, but you do have to read between the lines somewhat.

Yes traffic enforcement now is pretty much non-existent across much of the country. Traffic police divisions are a shadow of what they were 15 years ago, and that process begun before thousands of police were made redundant over the past 5 years. The police are in line for 30% cuts after the election too. They'll be very few forces able or willing to enforce traffic rules. To be honest many have pretty much stopped now.

If they were to focus on traffic offences then the reduced numbers mean other priorities will be cut. Burglary, theft?

So I think the hope is it will be supported by many driver across many different types of road and be self-policing, but when many realise that will it work?
 
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DaveHarries

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We have got 20mph limits going in here in Bristol, along with RPZs (Residents Parking Zones). All thanks to a mayor who is a complete [.....] and who takes no notice of what the residents are saying.

The Clifton area of Bristol recently got an RPZ despite a survey finding at least 75% of respondents against it and a petition of about 4500 signatures calling on reversal of its implementation. (Note: the Bristol suburb of Clifton, for anyone who doesn't know the area, contains a large number of shops, bars and cafes that people go to from outside the area). In another part of Bristol where there is an RPZ it was reported by the councillor for the area that some shops were reporting a drop in takings of as much as £130k.

http://www.bristolpost.co.uk/George...or-fiery-RPZ/story-26190148-detail/story.html

Anyway, back to 20mph: it is good that, fortunately, not every single road in the whole of Bristol is going to be 20mph. I can understand 20mph zones on narrow side roads and past schools but there are plenty of roads which are wide enough for 30mph and where there are no schools: one size does not fit all.

Also the police declared they would not enforce the new 20 zones but it is best to be careful if you see a marked van ahead. Saying that I did 27mph past one just before Christmas last year and heard nothing. Many people are taking no notice of the 20 zones. I also don't think that 20mph zones make for cleaner air as vehicles have to drive in lower gear.

The incumbent mayor stands to loose a lot of votes at best. Hopefully he will be thrown out at the next opportunity: roll on May 2016!

Dave
 
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jon0844

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I've spoken to a councillor who confirms that our odd situation with two different speed limits is because the road with the 20mph signs is as yet unadopted. The other end is adopted but the council won't seek the necessary order until the whole road is done and up to standard. This could be 2016.

As it stands, the road is set at 30mph and I'm told the signs can be ignored. Perhaps they should be covered up.
 

radamfi

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Many people are taking no notice of the 20 zones. I also don't think that 20mph zones make for cleaner air as vehicles have to drive in lower gear.

Is anyone claiming that a 20 mph limit leads to cleaner air? In my post above, I was referring to reduced pollution if you have a 50 mph limit rather than 70 mph. However, I would have thought that there would be scope for greater use of electric only mode at 20 mph when using a hybrid or especially a plug-in hybrid.

Even if others don't take notice of the 20 mph limit, you can observe it yourself and others behind will be forced to either stay behind or overtake (and in other words, blatantly ignore the limit). If you knock someone down in a 20 mph limit and the person dies or is seriously injured, questions will be asked if you were actually observing the limit. So why take the risk?
 

brianthegiant

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I also don't think that 20mph zones make for cleaner air as vehicles have to drive in lower gear
And?

If you apply a 20mph speed ceiling then people aren't accelerating hard out of junctions so vehicles are using less energy therefore they consequently must burn less fuel & emit less fumes.
kinetic energy = 0.5 x mass x velocity ^2
 

Busaholic

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Surely the main point about 20 mph limit as opposed to 30 mph is that average speeds will decrease from about 35 to about 25 mph, so the objective is largely achieved. The person doing 50 will,however, not go any slower.
 

Jonny

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And?

If you apply a 20mph speed ceiling then people aren't accelerating hard out of junctions so vehicles are using less energy therefore they consequently must burn less fuel & emit less fumes.
kinetic energy = 0.5 x mass x velocity ^2

In a lower gear, there is often more sound energy etc. produced - fuel efficiency charts show that the optimum speed is about 30mph.
 

jopsuk

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you got a fuel efficiency chart for a modern car that shows that?
 

Antman

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Surely the main point about 20 mph limit as opposed to 30 mph is that average speeds will decrease from about 35 to about 25 mph, so the objective is largely achieved. The person doing 50 will,however, not go any slower.

You've hit the nail on the head and the predictable old argument that nobody sticks to speed limits anyway is a red herring. Personally I have no objection to a 20mph limit in residential side streets.
 

Jonny

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you got a fuel efficiency chart for a modern car that shows that?

I can't remember where I put the proper chart, but the car's built-in computer does give better performance figures at 30mph (in otherwise equivalent steady-speed conditions) than at lower speeds.
 

Robertj21a

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If you are interested in obeying the speed limit, then you will have to observe your speedometer frequently whether the speed limit is 30 mph or 20 mph.

I find it quite disturbing that even motoring organisations pedal the myth that checking your speedometer is dangerous. Anyone who has had driving lessons from a reputable instructor will know that you have to keep your eyes moving constantly, so you would be glancing at your speedometer as a matter of course.

Most drivers know very well what speed they are doing without regularly checking the speedo.
--- old post above --- --- new post below ---
In a lower gear, there is often more sound energy etc. produced - fuel efficiency charts show that the optimum speed is about 30mph.

Really ? - can you provide a link please
 

radamfi

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Robertj21a:2140070 said:
Most drivers know very well what speed they are doing without regularly checking the speedo.

If that is the case then most drivers are blatantly ignoring the limit.
 

Domh245

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Really ? - can you provide a link please

Not 100% sure on my reasoning but in a lower gear, to reach the same speed, the engine has to rev higher. This means that more fuel is burnt (and because of the inefficiency of internal combustion engines generally) more heat and noise is produced. Perhaps using sound energy as an example of where the efficiency is lost isn't the best.


A quick google of "fuel efficiency speed graph" gives an interesting result. Most cars seem to operate most efficiently in the 30-50 mph region, but this will obviously change depending on the transmission, gearing, engine size, type of fuel used etc
 
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