14 January 2010

30 km/h Zones Work

As it turns out, I didn't get my christmas wish fulfilled. 30 km/h zone for motor vehicles in Copenhagen. Maybe the package is still in the post, but it isn't looking good here in mid-January.

Since wishing for 30 km/h zones - 20 km/h for school zones - there has been a bit of buzz about them. Barcelona is developing more 'Zones 30' based on positive results. A 27% reduction of accidents in one area of the city, for example.

Amsterdam has proposed a similar scheme, too and the Dutch Fietsersbond advocates them. The list of cities and towns lowering the speed limits is growing across Europe week by week.

In an inspired moment of excellent timing, The British Medical Journal published a paper about the effect of 20 mph traffic zones on road injuries in London. It was written by researchers at... The London School of Hygiene and Tropical Medicine... which is strange, but hey.

Effect of 20 mph traffic speed zones on road injuries in London, 1986-2006

Results: The introduction of 20 mph zones was associated with a 41.9% (95% confidence interval 36.0% to 47.8%) reduction in road casualties, after adjustment for underlying time trends. The percentage reduction was greatest in younger children and greater for the category of killed or seriously injured casualties than for minor injuries. There was no evidence of casualty migration to areas adjacent to 20 mph zones, where casualties also fellslightly by an average of 8.0% (4.4% to 11.5%).

Conclusions: 20 mph zones are effective measures for reducing road injuries and deaths.

Hang on... did they just say that we have an effective measure for reducing road injuries and death?! What are we waiting for then?

In this BBC article
, study leader Dr Chris Grundy, a lecturer at the London School of Hygiene and Tropical Medicine, said: "This evidence supports the rationale for 20mph zones, not just in major cities in Britain, but also in similar metropolitan areas elsewhere.

"Indeed, even within London, there is a case for extending the currently limited provision of such zones to other high casualty roads.

He estimated that 20mph zones in London save 200 lives a year, but this could increase to 700 if plans to extend the zones were implemented.

Talk of 30 km/h zones is often associated with quiet residential areas, which is fine and logical. I'm looking forward to seeing them in place all over Copenhagen and Frederiksberg. These zones are most effective in densely populated urban centres.

We have a new city council here in Copenhagen, and a new Mayor in charge of the traffic department. Here's hoping that the bicycle/pedestrian visionary-ness of the past four years continues.

This graphic is from this article on SF Streetsblog shows how big a difference speed makes.

Even the Danish Road Safety Council, in their usual [and tiresome] 'try and scare the shit out of them' style which really is soooo last century, have previously tackled the speed issue with their "Take the edge off your speed" campaign. The caption reads "what's your pain threshold?"

[an odd campaign, by the way... who are they speaking to? Motorists or pedestrians? Isn't quite clear.]

Tom Vanderbilt has a write up about this 20 mph/30 km/h business on his always excellent 'How We Drive' blog here. He mentions a website called Twenty's Plenty. A group in the UK who are fighting for lower speed limits.


Brent said...

In cities like Los Angeles, where I live, the general speed limit is 25 MPH, unless the street is otherwise marked. I've taken to asking people what they believe is the unposted limit, and I've been surprised at how few people know. Most people think it's 35 MPH!

SteveL said...

We in Bristol Traffic have been
recently denouncing our council's plans for 20 mph zones.

A review of the Portsmouth zones showed that splitting areas up into fast main roads and slow back roads didn't work. (That is the US model too). It stops people knowing what the speed limit is, makes using, crossing or walking alongside the main roads dangerous and splits up the 20mph zones into lots of little ones. And it makes it more expensive to roll out, as you have to pay for more signs.

The local council recognised this and so the the 20 mph zones will cover a lot of the inner city, with no exemption for main roads.

kfg said...

"The London School of Hygiene and Tropical Medicine... which is strange. . ."

Do you think that just because India and Burma are currently in the hands of the bloody wogs we're going to give up a cushy bureaucratic sinecure like this? NO!

We're going to redefine speed in Devon as a tropical disease amenable to hygienic amelioration, that's what we're going to do, by Jove!

“A somewhat counterintuitive observation is the apparently large reduction in injuries to car occupants.”

Because we're obviously of the British ivory tower idiocracy, and thus an intuitive sense of how to keep our bread buttered without actually contributing anything useful to society is in our genes.

Ummmmmmmm, yes, I AM feeling a bit (extra) curmudgeonly today; why do you ask?

Glenn said...

The speed limits on our little island in Washington State, USA are 40 MPH (65 KPH) on State Highway 116 and 35 MPH (55 KPH) on the other main road. I'd be happy to see 25 MPH (40 KPH).
The roads are narrower than the streets in near by towns and communities that have 20 to 25 MPH limits.
We are seriously thinking of getting a tandem, as our 10 year old daughter has outgrown the tag-along, and we are not willing to have her ride on narrow roads with little or no margins and cars and trucks travelling at 40 plus MPH.


Glenn said...

On our little island in Washington State, USA; the speed limit on the main road, which is a State Highway is 40 MPH (64.4 KPH), and on the other road, 35 MPH (56.4 KPH). I'd be happy to see 25 MPH (40 KPH). The roads are a good deal narrower than streets in neighboring towns and communities which have 20 or 25 MPH limits.
We are seriously considering a tandem, as our 10 year old daughter has outgrown the tag-along, but we are not willing to have her ride on a narrow road with little to no margins and cars going at 40 plus MPH.
Thanks for the blog, you give me hope.


Green Idea Factory said...

20mph/30km zones are widely implemented in Germany... apparently 80% of the streets in Berlin, but:
* That does mean that 20% of the traffic is moving faster than 30, because I am sure the majority of traffic is on 50km streets.
* Police enforcement is another issue entirely.
* Hardly anyone cycles as fast as 30km in town, especially on smaller streets, so cars still get a momentary advantage.
* Just like "naked streets" it can be a distraction for making streets carfree or really slow (like 7km).

So, I think 30km limits are great, but still not slow enough. German transport policy has a kind of have-your-cake-and-eat-it-to mentality or philosophy about private cars and think that there is no limit on how safe they can be, so, e.g. there are Emissions Zones in many cities but not Congestion Charging. OK, enough slagging.

tensaimon in okinawa said...

lots of 30kmh limits around where i live, if only they were enforced properly....

Some guy (an american serviceman, as it happens) tailgated me on my scooter and yelled at me for doing 35kmh in a 40km zone the other day in rainy windy crappy conditions. It felt like a pretty sensible speed to me....

Anonymous said...

yes kfg you obviously are feeling a little out of sorts and as several of my friends have been treated at London School of Hygiene and Tropical Medicine for diseases picked up whilst travelling that might have killed them I think your attempt at humour is inappropriate.

Mikael said...

I had the seats of my Citröen 2CV reupholstred at the The London School of Hygiene and Tropical Medicine's auto shop. Good price. The falafel's at their take away shop were nothing to write home about.

Anonymous said...

Here in Graz/Austria we have 50 km/h only on major roads and 30 km/h on all others (which of course is the majority). It's the only town in Austria with this models - in all other towns the general speed limit is 50 km/h, with some exceptions.

Now they start to reduce the speed from 50 km/h to 30 km/h near school, kindergardens, etc. But still I don't see any chance that they will reduce the general speed limit to 30 km/h.

People are used to driving fast (and they don't even realize that 50 km/h is FAST). I think it will take much more time until people understand that safety, silence and the possibility to walk/ride a bicycle are more important than driving fast.

James D. Schwartz said...

A Toronto City Councillor was blasted in September for proposing to reduce speed limits in this city by 10KM/h.


Most streets in the downtown core are 50KM/h currently, with some 40km/h school zones.

It seems like a no-brainer to me. Cars don't need to drive 50km/h on downtown streets - it's a ridiculous speed limit for the inner city.

Anonymous said...

Does anyone have any research demonstrating that a reduction from 50 to 30km/h will not cause significant congestion?? We need some stats to get more 30km/h zones in Australia, but decision makers are very congestion conscious...

Anonymous said...

A free search engine for transportation related papers. Unless you know someone at a university you might have to pay to get access to the actual papers. That said, a library might be able to help you for a lower cost than buying an article on-line.

Another resource is the Swedish Transguide which has an English version of the website. Some 13000 articles are available in full text and quite a few of them in English.

Using traffic flow theory you could say that the maximum capacity of the streets will probably decrease with 30 km/h vs. 50 km/h, but if that will cause significant congestions or not can not be said without further information about the current situation. Also how the intersections are affected by the speed decrease is important.

One thing you could use for arguing is that if the car speed is decreased to 30 km/h, it will be easier to form green waves that can be used by both cars and bicycles.

Jon_events said...

@SteveL - there is confusion in urban areas at the moment in the UK. There are lots of 20mph zones near to schools. Where I live there is one around the corner, some local residents didn't even know that they were living on a 20mph street as the school is on one round the corner.

If the default is 20mph in urban areas instead of 30mph, then the roads are much safer for all. It's much cheaper to roll it out without speed humps, just on road signage i.e. painting would be sufficient.

It also will encourage those who live in inner city areas to walk / cycle more instead of use their car. This will result in less congestion for those who still need to do so. My understanding of what happened in Portsmouth was a noticeable reduction in road casualties. NICE (UK heath commission body for those who are outside of the UK) did a report in November asking for 20mph limits in urban areas because of the evidence in casualty/death reduction.