How London Is Saving Lives With 20 MPH Zones

20__s_Plenty.jpgOne of London’s 20 mph zones, with physical traffic calming measures and the speed limit prominently displayed. Image: ITDP-Europe via Flickr.

When Mayor Bloomberg announced that the new pedestrian spaces in Midtown are here to stay, he made special note of the safety improvements on Broadway, which he called "reason enough to make this permanent." And after the mayor told reporters that the city was getting lots of requests for similar livable streets treatments, the speculation started: What’s next?

To replicate the Midtown street safety benefits throughout the five boroughs, New York could look to the example of the UK, where 20 mph zones have reduced automobile speeds across the country. The global city that perhaps most closely resembles NYC — London — has been installing 20 mph zones for the last decade, and they are saving lives. Already, 27 fewer Londoners are killed or seriously injured each year because of them.  

The standard speed limit in London, as in New York, is 30 mph. Since 2001, however, London has built more than four hundred 20 mph zones, as described in a 2009 report by the London Assembly [PDF]. The zones are located in residential neighborhoods or near areas of high pedestrian activity, like schools. As of last year, they covered 11 percent of the total road length of the city.

The safety effects of the 20 mph zones have been enormous for pedestrians, cyclists, and drivers alike. In London, serious traffic injuries and fatalities have fallen by 46 percent within the zones, according to the prestigious British Medical Journal. Deaths and serious injuries sustained by children have dropped 50 percent. There’s even a small spillover effect, with areas immediately adjacent to 20 mph zones seeing an eight percent reduction in total injuries and deaths. The science is so clear that in 2004 the World Health Organization endorsed 20 mph speeds as an essential strategy to save lives. 

These 20 mph zones do much more than change a digit on speed limit signs. London’s zones include a host of traffic calming measures to make the speed limit self-enforcing: road humps, raised junctions, chicanes, and raised crosswalks are the most common. Increasingly, speed cameras are used to enforce lower speeds.

When paired with hard hitting public service announcements like these, London is addressing each of the three E’s of traffic safety: engineering, enforcement, and education. As a result, the 20 mph zones really work, silencing skeptics who claimed that Londoners would just keep driving as they always had. As implemented, overall speeds in London’s 20 mph zones have decreased by nine miles per hour, according to the London Assembly report. Transport for London recently recommended
880 more sites for the traffic-slowing treatment.

London_20mph_zones.pngA 2008 map of London’s 20mph zones. Image: London Assembly.

Across the UK, the last few years have seen a shift away from engineering-intensive 20 mph zones and toward blanket 20 mph speed limits. Nationally, two million people now live on streets with 20 mph speed limits.

The impetus for this strategy came from Europe, said Rod King, the director of the national 20’s Plenty For Us campaign. While visiting a German town famous for its large population of cyclists, King was surprised to see that the town’s bike infrastructure wasn’t particularly developed. Instead, he said, "In the early 90s, they reduced the speed limit on all residential roads to 30 kilometers per hour," or 18.6 mph.

Inspired, King helped bring the idea back to the UK. After starting within the bike advocate community, the push to slow down cars quickly expanded. Advocates for pedestrian safety, public health, and even some safety-minded driving groups quickly banded together behind the idea. "It’s been accelerating dramatically in the last two years," said John Whitelegg, a professor of sustainable transport and a local councillor in Lancaster.

One benefit of changing an entire city or neighborhood to 20 mph speed limits is the cost, which King says may average 50 times less than London-style 20 mph zones. Another plus is that a uniform speed limit reduces confusion over constantly changing rules.

harestock.jpgCampaigning for slower streets in the town of Harestock, UK. Photo: Martin Tod/Flickr

Perhaps the most convincing argument for a blanket 20 mph speed limit is that it helps residents buy into the concept of driving more slowly. According to King, the fiercest opposition comes from those who have to drive through 20 mph speed limits but still live on fast-moving streets. "They don’t own the benefits of the 20 mph zone where they live," he said, "but they still have to pay the cost." When a large contiguous area is covered by lower speed limits, it’s easier for everyone to make the psychological switch to slower speeds.

Today, 20 mph streets enjoy widespread popular support.
The London Assembly noted that three-quarters of UK residents favor the use of 20 mph zones, though the country strongly prefers enforcement cameras to physical calming

Despite their current popularity, it wasn’t easy to make 20 mph roads a reality. After a 1996 report by the national Department for Transport showed how much safer slower streets would be, it took another three years for the national government to allow local governments to reduce speed limits without explicit approval. Political opposition was often intense. Many conservatives "take the point of view that the correct approach to road safety is just for parents to teach their children correctly," said Whitelegg.

Over the last few years, however, 20 mph speed limits have been sweeping across the UK. Portsmouth recently became the first British city where every residential street has a 20 mph speed limit, and nine others have already committed themselves to doing the same, according to Whitelegg. Eight of London’s 32 boroughs are moving towards a blanket 20 mph speed limit. The national Department of Transport is recommending 20 mph limits for all urban residential streets. 

Over a relatively short time, a broad swath of British cities and towns accustomed to 30 mph speeds have embraced the safety and quality of life that slow streets have brought. If any big city in America is ready to follow suit, it should be New York, where more people live without cars than in London.

  • As a London Cyclist I definitely support the 20mph zones. They make for much more pleasant cycling and often I’m even able to keep up with the speed of cars thus feeling more happy about claiming the lane. I would like to see them rolled out to more boroughs as and where it is appropriate.

  • The study didn’t check everything. It’s good that it tested for casualty migration to areas adjacent to the 20 mph zones, but that’s not all that needs to be tested for. The Smeed’s law analysis of traffic deaths as limited by drivers’ acceptance of risk would imply casualty migration all over.

  • Westchesterite

    Is this limited to cities (or dense towns)? Does this apply to, say, NYC suburbs?

  • I’ve long been amazed that in hundreds of American small towns drivers are held to speed limits of 25 or even 15 mph, but here in New York–where the roads can be even narrower and where, both as a percentage of population and definitely in terms of raw numbers, there are way more pedestrians–you can go 30 mph.

    To say nothing of my sense that in seemingly every little town I’m talking about there’s a cop parked diagonally in the bank parking lot just waiting for you to break the speed limit.

  • J:Lai

    I think the NYC DOT would need to make a massive shift in priorities. Despite some signs of changing priorities, they number one goal of the DOT still seems to be maximum throughput of motor vehicles.

    but if they did prioritize other modes and other uses for the streets, then some measures to encourage driving at slower speeds would be cheap and easy to implement. For instance, the timing of traffic signals could be adjusted to regulate the cars at 20 mph instead of 30 mph.

    Also, I though British speed limits were posted in kph, no?

  • James

    What difference does this make if motorists will just break the speed limit anyway? The UK is a different society, with a strong social contract and greater sense of community than we have here. In the New York area, cops generally give a leeway of about 10-15mph. Speeding is part of the culture here, beyond the border of any single municipality. Westchester is no different than the city proper. When I’m visiting friends and family in New England, I don’t dare go more than 5mph over the limit on the Mass Pike for fear of the ruthless Massachusetts State Police. Once I cross into the Tri State Area on the way home, the road reverts to being a free for all. Again, enforcement could be so much more than it is, but culture/tradition/apathy in this area dictates otherwise.

  • Chris Mcnally

    I think the key is not just an arbitrary speed limit which will be ignored but other traffic calming measures to bring the true speed to 20 MHP or under. ” London’s zones include a host of traffic calming measures to make the speed limit self-enforcing: road humps, raised junctions, chicanes, and raised crosswalks are the most common. Increasingly, speed cameras are used to enforce lower speeds.”

    In Brooklyn NY, where I live, every single street is a super highway with cars traveling as fast as possible. There is no such thing as a 20 MPH zone. The only way to slow cars down is to design the roads so speeding is not possible. the easiest way to do this it so make one way streets two way, and increase the size of sidewalks and other traffic calming features to reduce the width of the auto lanes.

  • BicyclesOnly

    Physical improvements to calm traffic are an essential complement to police enforcement, but simply changing the limit does change many people’s behavior. A substantial minority, perhaps a majority of NYC motorists will not exceed the speed limit by more than 10 MPH on the grid. So now they’re driving 40 MPH; reduce the limits to 20 MPH, they’ll stay at or under 30. Others who might be willing to exceed 30 in a 20 MPH zone will get stuck behind their more conservative fellow motorists. The overall effect would be to save lives.

  • People adhere to speed limits when they’re enforced. For example, when Sarkozy decided to crack down on speed limit infractions, French highway speeds fell. And when Carter lowered the speed limit, American highway speeds dropped to match it.

    Culture doesn’t really enter into it. British culture produced Margaret Thatcher. The middle class in Britain is so unconcerned with other people that New Labour had to fight poverty in secret, and trumpeted its record on crime reduction instead. The reason highway speeds in Britain are lower than in the US is that the government made a choice to enforce a strict speed limit, while the US government made a choice to tolerate 10 mph infractions.

  • In the future, we’ll remember that there’s no unalienable right to drive whatever speed you want and we’ll just set the limits to what we want them to actually be and them enforce them electronically (a bonus benefit from the system that will be charging motorists by the mile [variable rate by time-of-day, or traffic density of course]).

  • 20 mph zones in the UK and Europe are not simply *20mph speed limit* zones; they incorporate various other calming measures.

    BicyclesOnly is quite right, and in fact various studies bear out, that a speed limit reduction alone does not significantly lower speeds.

    However I don’t enjoy acknowledging that, because even in spite of it, I still very strongly believe that 30mph as the standard is wildly inappropriate for city streets, regardless of the effectiveness of the limit alone.

  • I’ve linked to the Bristol Traffic coverage of 20 mph zones. We have no data on the London scheme, but note that the Bristol Cycling Campaign was pretty critical of the Portsmouth project, because all main roads were exempted “because people want to drive fast there”. This misses the whole point of the plan: to make the roads you have to walk by, across and along safer, to make the main routes to get across the town places you can cycle.

    As a result, in Bristol, we are rolling out total-area 20 mph zones. Main roads and “residential roads” -a big chunk of the inner city will be 20 mph. As for enforcement, think cameras.

  • Onlineo

    J:Lai Britain is MPH not KPH. We have the metric system for everything apart from Beer (pints), road distaces (miles), speed (mph), height (feet) and golf distances (yards). It is rather silly and we may as well move 100% metric now.

    It has personally taken me about 4 years to come to terms with the 20mph zones. Until last year I used to challenge myself to see how fast I could drive through them safely. Culture has now caught up with the implemention of these zones and people started to realise that if you hit a pedestrian at 20mph they will be ok and you will be ok. If you hit a pedestrian at 35 mph they will be dead, you will have to live with the consequences and spend a few years in jail regardless of whether the pedestrain was in the wrong too (e.g. sleeping in the street or running accross the road without looking).

    All our local 20mph zones have large speed bumps, some also have chicanes or narrowing of lanes. Realistically you will crash or damage your suspension if you go much over 30mph through them.

    Our driving culture is not as free for all as the american but 95% of drivers still speed every day. Our police give you a leeway of 10% over the speed limit. We have a lot of enforcement camera’s but these are not on any motorway that has 70mph limit. In effect to be done speeding on the motorway you have to get caught either physically or by a mobile speed camera van on a motorway bridge. When not in a traffic jam many people just cruise at 90mph on the motorway slowly down to 75 for bridges with parked vans on them.

    Basically what I am saying is that if we Brits can get the 20mph zones to work, I think you Americans can too! New York is a wonderful city but even with these new pedestrianised spaces and bike lanes you feel far to squished on the narrow side walks. I would like to see roads closed completely to cars and opened up for bikes and walking. Simply Monday First Ave could be closed to vehicles, Tuesday Second Ave etc. Cars could still cross at the intersections, but at least 1 street north south per day would be very pedestrain and bicycle friendly!

  • BicyclesOnly

    Thanks for your informative and stimulating comment, Onlineo!

    I appreciate the open-minded and perhaps mishievious and spirit behind the “ciclovia roulette” concept with a different artery closed to MV traffic each day, but I think it would be a hard sell! I’m counting on the SBS improvements on First/Second Avenues (including lane reductions for bike paths and dedicated bus lanes) to calm traffic on the far East Side, at least a little.

    But your suggestions do dovetail with a few thoughts of my own, concerning Park Avenue north of the Met Life building (@48th Street).

    Put the “Park” back in Park Ave.!

    A variety of factors have caused upper Park Avenue to become a dangerous traffic-dominated throughway. Park sees lots of speeding because of its excess road capacity–it has 3 traffic lanes each direction, little slow-moving and double-parking commercial traffic to slow things down, and a “block”-based traffic signal sequence that rewards speeds in excess of 30 MPH. These features make Park a preferred N/S route for rush hour passenger cars compared to adjacent Madison and Lex, where double parking of commercial vehicles and buses effectively reduce the roadway to two or just one lane during the day.

    Between 1996 and 2005, there were as many pedestrians and cyclists killed on Park Ave between 59th and 96th (6) as on any other N/S roadway on the UES grid. Additional features, such as the width of the roadway and it’s two-way traffic, no doubt have contributed to make Park Ave. a leader in traffic fatalities. Yet community groups have opposed infrastructure that might save lives, such as bollards on the pedestrian refuge areas of the Park Ave. malls, on the ground that any change would detract from Park’s ‘iconic’ appearance.

    The answer is to return Park to the traffic-calmed boulevard it once was. The key first step is to reduce the speed limit to 20 or even 15 MPH. This should not rankle aesthetic sensibilities and with historic or modestly increased levels of enforcement will reduce speeds and save lives. Speed humps and narrowed lanes–virtually invisible infrastructure modifications– should be used to complement the reduced limit. Designate upper Park a class III bike route and explicitly direct motorists to allow cyclists to use the full right lane, except for turns. These changes would be accomplished primarily through signage and would not materially affect Park Ave’s ‘iconic’ appearance. In fact they would restore the grandeur of the original design by restoring the primacy of pedestrians.

    The non-residential portion of upper Park, from 48th to 59th, should have the right lanes converted to sidewalk cafe space, with one or two gaps per block where cabs and delivery vehicles can access the curb. Auction off these new cafe spaces to the highest bidders to generate maximum income for the city.

  • Check out how wide the Park Avenue medians are in this aerial photo (from 1924). Those look plenty “iconic” to me.

  • That map link is great Jonathan–thanks for sharing! Additional perspectives on the former, non-autocentric design of Park Avenue are provided here and here.

    Maybe in a generation or two, those who live on Park Avenue (or rather, those who purport to speak for them) might consider that the first design was really better than having a 6-lane highway run past their homes after all . . .

  • the speed limit, everywhere in every city should be no higher than 20mph.

  • “cochonthe speed limit, everywhere in every city should be no higher than 20mph.”

    Upon the broad north-south avenues, the East River Drive and the West Side “Hwy”?!

    The BQE?

    How many pedestrians would that help?

  • Mark Temporis

    I have some manner of ADD which makes boring things interminable, and driving slowly actually makes things more dangerous for me as I actually get distracted by non-road stuff (pretty girls, shiny objects, advertisements in passing windows, etc.).

  • LAifer

    When you consider that the average speed that vehicles travel, particularly during rush hour, from point A to point B is generally somewhere between 10-15 MPH anyway, if you could get lights better-synched to the 20 MPH limit you could actually improve average driver speeds while dramatically improving safety. Here in LA most artery streets are 35 MPH, which is actually 40+ when you factor in what people will drive, but then you hit light after light, which makes the actual speed somewhere below 20 MPH, if not closer to 15 or lower.


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