20 mph Zones

[waremark]

My objection is to the widespread use of 20's on what I see as arterial roads. As a regular driver in London I find it quite stressful trying to remember whether I am in a 20 or a 30 limit - on what I see as major routes with heavy through traffic. Of course I am happy to drive slowly on narrow roads with cars parked on either side - although even on such roads I think the main emphasis of road safety should be on teaching children how to use such roads safely, whether on foot, on two wheels or in a car. Use of 20's on through routes further slows already expensively slow travel times. I suspect it is too recent a development for there to be good data on the outcomes.

[RobC]

My objection is to the widespread use of 20's on what I see as arterial roads. As a regular driver in London I find it quite stressful trying to remember whether I am in a 20 or a 30 limit - on what I see as major routes with heavy through traffic. Of course I am happy to drive slowly on narrow roads with cars parked on either side - although even on such roads I think the main emphasis of road safety should be on teaching children how to use such roads safely, whether on foot, on two wheels or in a car. Use of 20's on through routes further slows already expensively slow travel times. I suspect it is too recent a development for there to be good data on the outcomes.

Decisions made for political reasons are not always correct.
The Green party campaigned for blanket 20mph limits across London without realising that 20mph limits aren't Green at all. Rather like the government encouraging us to buy diesel cars then telling us that diesel emissions are worse than petrol and should be banned from the capital.

This is one of the reasons I don't agree with blanket 20 mph zones.

http://www.theaa.com/public_affairs/news/20mph-roads-emissions.html

[TripleS]

My objection is to the widespread use of 20's on what I see as arterial roads. As a regular driver in London I find it quite stressful trying to remember whether I am in a 20 or a 30 limit - on what I see as major routes with heavy through traffic. Of course I am happy to drive slowly on narrow roads with cars parked on either side - although even on such roads I think the main emphasis of road safety should be on teaching children how to use such roads safely, whether on foot, on two wheels or in a car. Use of 20's on through routes further slows already expensively slow travel times. I suspect it is too recent a development for there to be good data on the outcomes.

Agreed, although I don't think the difficulty is confined to remembering whether we're in a 20 mph or 30 mph limit. From my observations I'd say that in some areas there are simply too many changes of limit (often for no apparent reason) over relatively short distances, and this can involve most of the range from 30 mph up to NSL. This cannot fail to divert some of a driver's attention away from the more important aspects of safe driving than the simplistic matter of speed limit compliance.

Summary: I fully support the principle of sensibly applied speed limits in built-up areas - generally 30 mph, or 40 mph where the hazard density is less, and the use of 20 mph zones in some residential areas, and in towns/villages where there are many pedestrians, parked vehicles and confined spaces. Having said that, I do not believe that speed limits are a 'key factor' in the maintenance of safe driving. Speed limits in themselves can not possibly lead us to identify a safe choice of speed: they are a very crude guide, and often wildly adrift from an actual safe speed.

Best wishes all,
Dave.

[Silk]

You can argue as much as you like that you can travel safely at higher speeds than the normal Joe or Jane but the world is made up of Joes and Janes and not Alastairs.

I don't see anyone arguing that at all. It just shows your ignorance. Just to be clear "advanced" driving is not about using "special powers" in order to go faster than other drivers, it's more about identifying hazards and driving accordingly - this means driving up to the speed limit when it's safe, but driving well below when it isn't. In fact, you're more likely to find it's the "advanced" driver who is already going slowly in residential streets without the need for a lower speed limit.

My worry isn't about 20 limits in streets where it's inappropriate to go any faster anyway, but how they will be enforced. I doubt well see any speed cameras situated in streets with children playing - they'll be on roads where a 20 limit isn't necessary but happens to fall within a zone. They'll be where drivers have been driving below 20 through the residential area but let their guard down when the road opens out when leaving the area, but the limit still applies.

Here's an idea. Why don't you approach your local Advanced Driving organisation and see if you can get a demonstration drive, or even sign up for a course yourself? Failing that, you could always attend one of the ADUK driving days. I promise no one will attempt to pelt you with rotten fruit.

[jcochrane]

On part of one of the routes I use to commute to London a red ring 20mph limit has been recently introduced. It lasts for 5 miles There is only one short break in the blanket limit when it reverts back to 30 and is ten yards before a crossroads. 5 yards the other side of the crossroads it returns to 20 mph. For most of this route the road width varies from 3 lane to 6 lane, most of it 4 lane. I'm travelling through at 5 o'clock in the morning with very little traffic and virtually zero pedestrians.

This has to be a typical case of utter stupidity.

I am strongly opposed to pressure groups for the 20 mph blanket limits. However I am fully supportive of sensible speeds limits of 20 mph, or even less, but there needs to be far more thought into both the time and place of such limits. A maximum 20 mph speed limit at a school during school time is not unresonable and in some cases even a maximum 10 mph or even 5 mph would be more appropriate. For example a small primary school close to me is on a narrow, wooded lane in a residential area with parked cars on either side. Parents dropping children off and parking badly make the situation even worse. Until recently there was not even a zebra crossing. A zebra crossing and a 20 mph limit is now in place but the limit is far to high during school opening and closing times. Even 5 mph is pushing safety margins. I would fully support a maximum 5 mph limit for these high hazard periods. But blanket 20s? No way do they get my vote they can have a positive or negative impact on safety when implimented in this thoughtless way. Making one arbitary limit of 20 mph to cover all situations is utter foolishness bordering on the irresponsible demonstrating little thought to safety and what might be an appropriate maximum speed for a given time and place.

[akirk]

This is one of the reasons I don't agree with blanket 20 mph zones.

http://www.theaa.com/public_affairs/news/20mph-roads-emissions.html

and this is one of the reasons we must challenge campaigns such as Rod's:
compare the above with:
http://www.20splentyforus.org.uk/pollution.htm

On his website he is quoting sources from the mid 90s - how relevant is that to modern cars?

Choice of gear and driving style, not the number on the speed limit sign, most affect fuel use[3]. DfT guidance states, “Generally, driving more slowly at a steady pace saves fuel and carbon dioxide emissions, unless an unnecessarily low gear is used”.

what is an un-necessarily low gear? at under 20mph I am in 1st or 2nd - if I am in 4th I am sure that fuel consumption will be less, but I am not in an appropriate gear, and not safe.

The likelihood of modal shift to non polluting modes due to better safety brings reduced fumes. Each trip transferred from a motorised vehicle has a fuel consumption of 0mpg and less noise. Plus reduced congestion and standing traffic, which pumps out more emissions than moving vehicles.

Starting to see their true colours - get people out of motorised vehicles - this is basically an anti-car campaign pretending to be about safety!

A report from Belgium[4] concluded "It is unlikely that imposing strict speed limits in urban areas has a significant influence on emissions of NOx or CO2."

well that is conclusive then

Typical of a shoddy campaign - a page presenting the 'facts' which is a list of out of date suppositions not backed by focused research - and we allow our country to be influenced by amateur campaigners like this?

lets not allow facts to get in the way of someone's crusade...

scary what we allow in the UK

Alasdair

[Pontoneer]

As far as I am aware - both are equally enforceable - as martine says, one is an area wihtin which the structure is meant to keep you down to 20mph, so they don't need to keep telling you, but they tell you on entry and exit - e.g. a houseing estate might have this...
a 20mph limit is simply a bit of road on which a decision has been made to make the speed limit 20mph and signs / repeater signs / etc. are now needed...

of course if you are on a bike you can ignore both - unless cycling furiously

Alasdair

I seem to recall reading that , when first implemented near to me , the few '20 limits' were advisory only , as they had no statutory basis and the actual speed limit remained at 30 ; however if an incident occurred where a speed above 20 might have been a factor then this could be taken into consideration .

I wonder is there a penalty code ( similar to SP30 , SP50 etc ) for exceeding a '20 limit' ?

[Mr Cholmondeley-Warner]

Alasdair, I doubt if you'd be in 1st or 2nd unless you artificially restricted yourself to that. 3rd should work perfectly well for a steady 20. In your automatic it might even use 4th from time to time.

Re "journeys transferred have an effective mpg of 0" - typical environmentalist utopian stuff. We walk everywhere, or cycle, (including people's commute to work - averaging 15km in 2011, and increasing all the time). Yeah, right! Last time I looked, most public transport used diesel (apart from electric rail that pollutes in a different way), and is not available on most people's doorstep, requiring a combined transport journey, extra parking (or multiple journeys if dropped off at a public transport access point such as a station), and so on. Only really practical for Londoners or other large conurbations.

[Pontoneer]

The 85th percentile test seems to have been abolished in favor of political expedience and pandering to aggressive lobbying from certain organisations who seem to think we should all be walking or driving at no more than walking pace

The 85th percentile has indeed been officially abolished as a way to set speed limits. Local councils have been give much more freedom to implement lower speed limits as they think fit with few restrictions/recommendations. The guidance from DfT to councils was to review speed limits with a view to adjust limits both ways (decrease and increase) but the latter is extremely rare in my experience.

It isn't as easy as all that .

The road outside my home ( less than 50 yds from a series of bends on a busy rural A road ) was the scene of a significant number of crashes following resurfacing ( I counted something like 18 over a 14 month period , had one intrusion into my driveway , writing off a car , and another car written off in front of the house one week later ( caught that one on video ! ) as well as my neighbour who told me she had had something like 22 cars in her garden since she moved in and a front porch demolished ) ; I started documenting these crashes with photographs and ended up with a three page spread in the Glasgow Evening Times , following which the council came out and laid 'Shellgrip' throughout the bends . Many of the crashes were damage only ( including two of the three cars that ended up in our septic tank ! ) but there were a number of casualties , including one serious where a driver sustained two broken legs in a head-on crash . Since there was also a crossroads just beyond my house , which was also the scene of crashes , due to vehicles coming out of the last bend at speed and being unable to stop if someone was waiting to turn right , I also asked for a reduction in speed limit from NSL to 50 or even 40 , but was told bluntly by a traffic officer who called round that it was unlikely to happen unless someone was killed !

So despite having a well documented list of incidents , there was great reluctance to change the speed limit .

Strangely , there have indeed been two recent fatalities a mile or so along the road on a completely open and straight stretch .

The Shellgrip has pretty much eliminated the crashes in/coming out of the bends , but we still have had a few at the crossroads ; I also sometimes have to step on it quickly if I am halfway across the road , coming out of my drive , and something appears at speed - although usually one can hear them coming before one sees them , especially the motorbikes which are often laid well over at high speed and not in much of a position to stop ( there are warning signs for the bends and the crossroads posted further back ) .

In fairness , most drivers do drive fairly safely and reasonably , but there are still too many who don't .

[Gareth]

I doubt if you'd be in 1st or 2nd unless you artificially restricted yourself to that. 3rd should work perfectly well for a steady 20. In your automatic it might even use 4th from time to time.

In either of our diesel Skoda cars, and even in our petrol Alfa, I would typically be using 1st or 2nd to travel at 20 mph or less, (2nd at 20 mph, definitely not 3rd). Indeed, I'm often enough in 2nd in a 30 mph limit, (2nd definitely up to ~27/8 mph, sometimes higher if there's a particular need).

[Mr Cholmondeley-Warner]

I doubt if you'd be in 1st or 2nd unless you artificially restricted yourself to that. 3rd should work perfectly well for a steady 20. In your automatic it might even use 4th from time to time.

In either of our diesel Skoda cars, and even in our petrol Alfa, I would typically be using 1st or 2nd to travel at 20 mph or less, (2nd at 20 mph, definitely not 3rd). Indeed, I'm often enough in 2nd in a 30 mph limit, (2nd definitely up to ~27/8 mph, sometimes higher if there's a particular need).

Well you and I differ there, and I suspect so does most of Joe Public. 2nd at 28 mph is quite a lot in a diesel - I'll try it later this afternoon and see how many revs it equates to in the Peugeot, but I suspect it'll be 3500 ish. Why would you be revving the engine to that level to travel at a steady speed? (Note I'm not talking about accelerating through the gears to a higher speed). I remember you telling me maximum torque in your car was at 3200 ish, and being quite evangelical about changing up at or before that point. Your tune has changed

My 308 is fairly petrol-ish in that it prefers to be in 3rd at 30 than 4th, but it'll still work in 4th, just that the revs are below the turbo threshold, so there isn't much instant acceleration available.

[Gareth]

Starting to see their true colours - get people out of motorised vehicles - this is basically an anti-car campaign pretending to be about safety!

Campaigns are supported by a variety of people for many reasons, but you might imagine that there's a large swathe of popular support from people who also support BRAKE. Assuming that's so, then the success of a particular campaign will be predicated on continued support from the majority of its supporters, so in turn the organisers will tend to include words and phrases in campaign material with that in mind. Gaining and maintaining support is just a means to an end, not necessarily directly related to the views of the organisers iyswim.

[jont]

I wonder how many 20mph zone supporters would continue to support them if they were required to have 20 mph speed limiters fitted to their vehicles which activate in these zones? I can't help but think the majority of supporters only want everyone /else/ to do 20mph, while they carry on much as before.

[Gareth]

I remember you telling me maximum torque in your car was at 3200 ish

Max torque is at 1900, max power is at 4000, if I remember correctly. I'll check the engine speed in 2nd at 20 mph and report back later.

Regarding diesels ... one issue for me is driveability; pick a higher gear and the engine speed is too low, compounded by bigger gaps in the ratios in (some?) diesel cars. Another is engine longevity; I try to follow a recommendation from someone who has rebuilt many PD engines, to keep above 1500 rpm.

The changing up thing, again diesel related; I've been working through a lot in my head - I think the main issue before was that people don't tend to accelerate using WOT (from above peak torque).

[jcochrane]

With my Peugeot 208 1.6 diesel at 2000 rpm in 2nd gives me 20mph app, 30mph in 3rd and 40mph in 4th. Max torque 1700 rpm. Given the density of London traffic, on a homeward commute, speed typically varies between 5-25mph. 2nd and 3rd gears are therefore the most used gears. Only when you have assertained that you can cruise at 30mph with no likelyhood of needing to accelerate would 3rd be selected. It follows that keeping to a 20 mph limit would require 2nd gear in the main, for flexibility, with an occasional short shift to 3rd where hazards and no or little acceleration is likely.

The question of speed limits has only minimal relevance in London anyway as traffic density (and its greater related risks) has a major influence on the general speed of traffic.