Road Safety News

Momentum building for 20mph limits?

Tuesday 15th May 2012

With more councils implementing 20mph limits on residential streets, a Guardian Bike Blog asks whether the limit could soon become as widely accepted as the smoking ban in pubs.

Portsmouth, Oxford and other cities have pioneered the switch within the past five years, and campaigners from the 20's Plenty For Us movement say eight million people now live in areas committed to adopting the limit for residential roads.

But, according to the Guardian blog, the most significant recruit to the cause may turn out to be Liverpool, where the local NHS trust will pay £665,000 over four years to implement and study an extension of the city's 20mph limits to a majority of streets.

The blog notes that nobody yet knows if injecting money from the public health budget will pay back in reduced hospital costs for treating victims of road accidents, but it could be the start of a trend.

From 2013, councils will take on larger responsibilities for public health in England. The idea, says the blog, is that lowering road speeds may cut the NHS bill for treating crash victims, and also combat obesity by encouraging more people to walk and cycle.

Until last year most of the enquiries handled by the 20's Plenty movement came from individuals and campaigners. However, Rod King, its founder, says that in 2012 more than half the inquiries have come from local government. But while momentum appears to be growing and all three major political parties are supportive, the Government is against legislation.

Norman Baker, junior transport minister, recently said: “It is not Government policy to have a default limit. This is a matter of localism. It would be wrong for us to impose our view from Westminster and Whitehall; those days are ending, I am happy to say.”

Mr Baker says he wants councils to think hard about 20mph limits, and is trying to make implementation easier and cheaper by simplifying guidance on signage and scrapping the previous requirement for extensive physical traffic calming.

However, Chief superintendant Jerry Moore of ACPO says that the police will not support 20 mph limits unless they are self-enforcing: "Simply altering the signs and lowering the limit and dumping it on the police is inappropriate," he said.

Campaigners say evidence from Portsmouth and elsewhere shows strong public support for 20mph limits, with up to 80% of residents backing the change. They also say that complaints from motorists that their fuel consumption and their journey times will rise steeply are based on myth.

Click here to read the full Bike Blog.


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The 20's Plenty campaign promotes the view that "if you hit people at slower speeds you kill fewer of them". This approach has no place in any serious assessment of road safety, as I made clear during my presentation to the recent 20mph Places Conference at the start of May.
Eric Bridgstock, Independent Road Safety Research, St Albans

Agree (3) | Disagree (6)

It is disappointing to have to spell things out but I am of course talking about reduction of the speed of all traffic, not just injecting one crippled vehicle into an otherwise racetrack environment. I defy anyone to demonstrate to me that, if you take a cohort of inijury collisions and re-run them with every vehicle's speed reduced, there won't be fewer collisions and fewer, less severe casualties. This is the essence of traffic calming and it has been shown over and over again to be effective. I am contrasting it with simply changing the speed limit and allowing drivers to exercise their discretion which, in my view, is less effective as a means of casualty reduction. The saddest part of recent posts is the suggestion that travelling below the speed limit somehow entitles a following driver to conduct a dangerous manoeuvre in order to overtake. Not unreasonably? I think not!
Tim Philpot, Wolverhampton

Agree (6) | Disagree (0)

Tim Phipot's "actual reduction in speed will reduce casualties" is a sweeping generalisation and as such demonstrably wrong, for instance:

Try driving 100 miles on a motorway at 45mph as I once did with a sick engine - never again, I assure you.

Try driving at 40mph on a 60mph A road and see how many times you are at risk as others, not unreasonably, have to overtake you.

49 cars doing 49 mph and 1 car doing 100 mph have the same average speed as 50 cars doing 50mph - does anyone think that the risk is the same? This incidentally is just one example showing that TRL 421, the fabled +1mph - +5% risk is and always was fantasy. In any case it referred to very particular circumstances yet is now widely quoted by anti-speed people as an universal rule.
Idris Francis Petersfield

Agree (6) | Disagree (9)

I would be interested to see Ms. Seymlyn's analysis leading to a 800% return on investment in Warrington - I suspect it will be based on DfT's "Fantasy Economics" figures for lost output that is not in fact lost - see my previous posts and

She is however quite right that the reduction in average speed is of itself not a reliable indicator because, as always, averages can hide all sorts of nasty extremes either way. However as I pointed out 3 years ago when assessing Portsmouth's bogus claims (see, if the average changed very little, but on some roads speeds fell significantly, it is arithmetically inevitable that speeds rose significantly on other roads.
Idris Francis Petersfield

Agree (3) | Disagree (6)

Please note that Anna Seymleyn, who commented earlier, is closely involved with 20'S Plenty.

In regard to 20mph areas, sorry, the tide has already turned as Councillors are seeing through the propaganda and invalid claims of success - see for example for how the results in Portsmouth, claimed as success, were in reality worse or far worse than trends in the rest of the country.

At the recent 20's Plenty Conference the organisers were visibly less than pleased when at least one speaker showed damning evidence that (as so often) impressions of success have been conjured out of actual failure by cherry-picked data and incompetent analysis, for example ignoring traffic diversion, long term trends and better trends elsewhere.
Idris Francis

Agree (7) | Disagree (5)

Doesn't really matter. All roads in towns and villages will be 20 mph from 2015 as part of measures by this country to reduce to nil the fatalities and incident rates in all EU States by 2020.

Doesn't matter if it works. This government is already implementing measures which will enable local authorities to detemine their own speed limits (and that will be in line with the government's recommendation of 20mph) without the need to go through any legal process and cost and without involving Westminster as they have to do at this moment in time.

Indeed, some authorities have no doubt jumped the gun and imposed such speed restrictions without Westminster's approval.
bob craven Lancs

Agree (0) | Disagree (0)

Warrington's 20mph speed limit trial shows mean speeds reduced 0.9 mph overall and casualties fell by 15% but it doesn't look like they've adjusted for national trends or traffic flow. Once that's done, it looks as though results might be worse than where limits remained at 30mph. And, like Portsmouth’s 20mph, killed and serious injuries went up in Warrington's 20mph. Have results improved since then?
Dave Finney - Slough

Agree (8) | Disagree (3)

The 800% rate of return on investment in Warrington's 20mph pilot was huge. So I disagree with Pete. Stating the 1.3mph average reduction in speed isn't useful. Many roads stayed the same at around 20mph. The interesting fact is that the faster roads in the 25-29mph pre limit were reduced by 6mph. This is an important difference in perception of safey and respondents said they felt safety had improved. I agree with driver liability.
Anna Semlyen, York

Agree (2) | Disagree (8)

Firstly any "new" money is great, I've long argued that authorities are operating in a closed bubble and if the NHS can get future savings by expending now, then it's good that they want to do this.

But I am somewhat amazed that in Liverpool the FIRST type of project off the shelf for this finance model is 20mph signed only limits when there would likely to be more benefits to be achieved from spending public money on junction safety improvements and other AIP priority sites. On the plus side it seems that Liverpool will invest in monitoring so at least we should be able to compare the returns. Most current evidence suggests that returns from signed only 20 limits are modest and weaker than other types of safety scheme.
Pete, Liverpool

Agree (2) | Disagree (0)

There are myths propagated on both sides of this debate, some I think even invented just to discredit the opposition. But does anyone seriously believe that reducing average speed in Portsmouth from 19.8mph (2008) to 18.5mph (2010) will so alter people's perception of safety that those who were previously afraid to walk and cycle in the streets will as a result feel safe to do so? The wide disparity of results between the different sectors of Portsmouth should be proof enough that a default 20 limit is not a universal panacea. I could not possibly disagree with the notion that actual reduction in speed will reduce casualties, but where targetted use of more effective measures than 20 limits can yield better results they should be used. Most supporters of the 20 mph campaign bear no responsibility for the outcomes of their campaigning. But if they really wanted safer streets they would be campaigning for the law to make the driver automatically culpable for injury in a 20 limit unless proven otherwise. On that day everyone would be doing 19 and paying full attention.
Tim Philpot, Wolverhampton

Agree (4) | Disagree (1)