How London Is Saving Lives With 20 MPH Zones

One 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.

A 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.

Campaigning 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
measures.

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.