Are 20mph limits the right approach to reducing injury accidents?

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As a local councillor I have been bombarded by emails from campaigners calling for blanket 20mph limits on urban roads. The campaign run by a City of York councillor has this to say:

We quite simply campaign for 20mph to become the default speed limit on residential and urban streets. This can be done on most streets without the need for any physical calming and we accept that on some streets it may be appropriate to have a higher limit based on the road, vulnerable road users provision, etc. But any limit above 20mph should be a considered decision based on local circumstances.

This is very different from the introduction of 20mph zones (usually accompanied by traffic calming measures) in particularly high risk places such as village centres and outside schools. What the campaigners call for is a change to the default speed limit in urban areas.

While I have supported 20mph zones (we have one in Harden, for example, that not everyone is keen on), I am sceptical as to whether the introduction of a general lower speed limit will work as the campaigners suggest. The core argument appears to be the 'laws of physics' - essentially that there will be fewer casualties as a result of slower speeds and where collisions occur they cause less harm.

Campaigners also point to the case of Portsmouth where casualties reduced by 22% in the three years following the introduction of 20mph limits. However, the evaluation report (where the 22% figure is found) also showed that 'killed and seriously injured' figures rose during this period. And the reports authors also concluded that:

...overall, improvements in casualty rates were not demonstrably greater than the national trend, and that 20 mph zones were more effective at reducing average traffic speeds.

 This suggests that 20mph limits might not be the best way forward and that the current approach where zones (supported in most but not all cases by physical intervention as well as signage) are targeted to high risk areas is a better option. This reflects the fact that most of our urban roads are pretty safe with very low - even zero - rates of injury accident.

To help us understand this, if we look at the map of Cullingworth's RTAs from 2000-2010, we find that they are entirely (bar one outside the school gates) on the main roads through the village. This indicates a case for looking a 20mph zones in the village centre (although only five of the accidents involved either pedestrians or cyclists) but does not support a general 20mph limit. Looking in more detail at Bradford, we see that the inner city and especially main roads through the inner city are the most lethal for pedestrians. I would take the view that safety cameras are perhaps a more effective means of managing speeds than 20mph limits without accompanying traffic calming measures.

The proposal for 20mph limits seems to me an honest attempt to develop what we might call an 'all-population' solution to injury accidents on our roads - reduced speeds mean fewer accidents and less deadly accidents therefore reduced speed limits everywhere would achieve this end. However, the RTAs are concentrated not spread evenly across the network. So there is no need for the general reduction. Instead, we should use targeted interventions (easily enforceable, local 20mph zones with physical calming measures) in the most high risk locations. And we know these work.

A bit like minimum pricing for alcohol, blanket 20mph limits have an initial appeal. However, they do not address the problem directly and act to reduce speeds where speed reduction isn't needed and don't provide the active calming measures we know are most effective in high risk locations. Lastly, we need to consider who is causing the injury accidents and wonder whether our current enforcement system is entirely adequate:

For every fatal collision, there is a one in two chance that the driver responsible has a criminal record, according to preliminary research by South Yorkshire police.

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It was either this or a red nose...

Via the brilliant Pop-up City we discover that the Finnish Reindeer Herders Association is trying out a new way to reduce the estimated 2000 plus reindeer-related road accidents:

A new experiment involving the protection of free-roaming reindeer may just be inspired by Rudolph’s most virtuous characteristic. The project involves coating reindeer antlers with a specially formulated glow-in-the-dark liquid that aims to reduce reindeer-related traffic accidents.

Does make Rudolf's nose redundant though!

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Thoughts on cycling...

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I've got a bike. You can ride it if you like.
It's got a basket, a bell that rings and
Things to make it look good.

I don't cycle. Indeed I gave my bike to my son a week or so back for him to travel to and from work. I used to cycle, back in the days when cycling five miles to school in South London was a done thing (and when schools, famously, had bike sheds behind which you could smoke).

So I was curious about the recent modest hullabaloo about cycling accidents where, if I understand correctly, they are all the fault of Boris Johnson.

The thing is that the number of cyclists involved in accidents has increased as the number of cyclists has increased. The CTC reports that the mileage cycled has increased by 20% over the past decade and that around 750,000 people regularly cycle to work.

It may be that, as numbers of cyclists increase, awareness levels increase too - both because cyclists are more expected on the roads but also that more drivers are also cyclists. And some research supports this contention:

The likelihood that a given person walking or bicycling will be struck by a motorist varies inversely with the amount of walking or bicycling. This pattern is consistent across communities of varying size, from specific intersections to cities and countries, and across time periods. (Jacobsen, 2003)

So more cycling means lower risks (although not necessarily fewer injuries in absolute terms, which is the reason for the silly spat over Boris) for cyclists but not for motorists.  The question is whether there's a point at which the critical mass of cyclists has sufficient of an effect on driver behaviour to begin to see the risks for the motorists fall as they are for the cyclist.

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Nothing is that straightforward, Johann - the case of speed cameras

As ever with reporting on research we can be easily lulled into accepting the headline figures and the results that appear always to substantiate the view of authority. So it is with speed cameras. Here’s the oft wrong, Johann Hari on the subject:

We have the independent academic studies. We have reams of them. They all say the same. To cite the most detailed: a four year on-the-ground scientific study by University College London* found that when you set up a speed camera, the number of people killed in that place falls by 17 percent, over and above the general decline in road accidents that is happening everywhere because of improving technologies like airbags. That’s 100 people saved from death every year nationwide, the equivalent of stopping two 7/7s, or six Dunblaine (sic) massacres. Oh, and over 4000 people saved from serious injury.

Case closed says our friendly left-wing journalist. You lot – you speeding, middle-class drivers, you budding Clarksons – you are in the wrong. Speed cameras are saving the lives of countless kiddies and grannies across the length and breadth of England. Or is this actually the case?

Well maybe not.

There are many possible reasons which may contribute to the recent large reductions in fatalities. The economic downturn and falling traffic levels for the last two years have played a part. Similar large falls in fatalities were seen in the recession in the early 1990s.

We should also note that there has been no observable change in the long-term trend of reducing pedestrian casualties. If speed cameras were so effective then we would expect to have seen an accelerating rate of decline. Especially given that many cameras are installed with the express intention of reducing pedestrian casualty risk.

The big contribution to the decline in casualty rates is in the numbers of 16-25 year olds killed:

The number of fatalities in accidents involving young car drivers fell by 11 per cent from 635 in 2008 to 564 in 2009 – a reduction of 71 deaths, out of a total fall of 316 road deaths between 2008 and 2009. This follows a 22 per cent fall between 2007 and 2008 – a reduction of 182 deaths.

All this comes from Department of Transport figures and studies – the same studies that report every year how the main contributor to road casualties is sloppy behaviour:

The contributory factor category driver/rider error or reaction was the most frequently reported category, involved in 69 per cent of all accidents reported to the police. It was the most frequently reported category for each severity of accident

And for pedestrians:

Pedestrian failed to look properly was reported in 58 per cent of accidents in which a pedestrian was injured or killed, and pedestrian careless, reckless or in a hurry was reported in 23 per cent. Eighteen per cent of pedestrian casualties had both of these factors reported.

It may be that speed cameras save lives. But the UCL research – for all its significance (and we’ll ignore that it was paid for by the advocates of speed cameras shall we?) focuses on point studies. And even at the most dangerous point in the country the numbers of injury accidents is too small for any trend not to be meaningless.

If we’re looking for causal factors in all this – for the thing that is causing the most accidents – then we must look at the numbers or men under 30 driving on our roads. For it is these young men who are most likely to cause and to be involved in serious accidents. If Johann Hari really cares so deeply about road safety that he thinks freedoms can be infringed – then he should be advocating banning young men from driving.


*See Mr Hari, it’s not hard to find the link to the research you reference and put it in your blog post. And save us folk half an hour or so trying to find it.

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A road safety strategy should be about reducing road casuaties? Not according to some!

Cullingworth will soon be further adorned by Vehicle Activated Signs (VAS) telling us to slow down as we enter the village - initially from Bingley & Keighley. Leaving aside that one of these signs - at Cow House - is in perhaps the daftest location one could imagine (plonking something that intermittently flashes on and off just six feet from someones bedroom window is not really appropriate), I have been thinking about the way in which we approach road safety. And crucially whether, in responding to the calls from local people, we spend money in places where there are few if any injury accidents.

Steve Thornton, Chair of the West Yorkshire Safer Roads Partnership recently criticised the Government's proposed approach to road safety as concentrating too much on reducing road injuries. Now far be it for me to criticise Mr Thornton - who is after all an expert - but isn't a road safety strategy absolutely about reducing road injuries? There is no "wider context" - the object is to reduce the death and injury toll on our roads and anything else is just cant.


And (no surprises here) the West Yorkshire Safer Roads Partnership is one of those obscure, unaccountable bodies which doesn't meet in public, doesn't say when it meets and doesn't publish any minutes, budgets or other operational information. Yet its "Chair" - an unelected official - gets a very public platform to criticise the very sensible suggestion that road safety is about...er?...safety on the roads!