Wednesday, 10 October 2012

20mph: A snapshot of the evidence

A new survey commissioned by Sustrans shows that 70 per cent of British people want the speed limit to be dropped to 20 miles per hour in residential areas to make them safer. But it’s not just public opinion that supports an area-wide roll out of 20mph - the evidence of the safety, health and economic benefits is irrefutable. Safer streets There were 405 pedestrian and 111 cyclist deaths in Britain in 2010, yet we know that reducing speeds saves lives. When the Transport Research Lab (TRL) reviewed 250 20mph schemes across Great Britain they found that accidents per year fell by 60%1, and a recent British Medical Journal study showed that the introduction of 20mph zones was associated with 42% fewer road casualties. Younger children were the main beneficiaries in this reduction in causalities, and serious injuries and fatalities also dropped significantly. A better place to walk and cycle High vehicle speeds are the greatest deterrent to walking and cycling. Reviews show that reducing speeds to 20 mph (30 km/h) encourages more people to walk and cycle3. A 20 mph speed limit in built-up areas allows for the safe mixing of motorised and non-motorised modes of transport, and makes it easier for pedestrians and cyclists to enjoy the same direct and safe routes for their journeys as motorists. Smoother traffic flow, reduced congestion and cheaper fuel When 30km/h zones were introduced in Germany, car drivers changed gear 12% less often, braked 14% less often and required 12% less fuel4. Research also showed that driving at a steady 30 kph reduces vehicle emissions as braking and accelerating between junctions and other obstacles decreases. Sociable places Heavy traffic damages communities – and the speed of traffic plays a key role. A study from the Commission for Integrated Transport found that where cities have 20 mph speed limits covering between 65% and 85% of the street network, they are transformed “from being noisy, polluted places into vibrant, people-centred environments.” Economic benefits There are clear financial benefits to 20mph. In 2010, the estimated cost to the economy of collisions in Britain was around £15 billion.7 Conversely, area-wide 20mph limits are low cost and high benefit. For example, Portsmouth converted 1200 streets in the city to 20mph for a cost of just over half a million pounds whilst Transport for London (TfL) estimates that the 20mph London’s zones are already estimated to be saving the city more than £20 million every year by preventing crashes.

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