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Transport / Mass transit

Birmingham is considering a 20mph speed limit in the southern half of the city. Will it work?

Birmingham City Council, the largest local authority in Europe, has announced proposals to implement 20 miles per hour speed limits on roads across much of the southern half of the city. It has already enforced reductions from the 30mph limit on roads near schools; but now there’s growing support for a wider rollout.

Emergency vehicles like ambulances will be exempt – but the hope this that wider 20mph limits will persuade drivers of other vehicles to better share the road with each other, pedestrians, and cyclists. The rationale behind this in Birmingham applies to any other city in the country: the authorities want to reduce the severity and number of accidents. They aim to lower air and noise pollution, too.

Previous consultations showed stronger support from those who walk, cycle, and use public transport – so convincing those who primarily drive will be the key challenge. There is also widespread support amongst other key stakeholders: businesses, schools, the police, environmental groups, and transport and delivery groups.

Evidence from several towns and cities across England shows that the implementation of 20mph limits reduces the number and severity of road traffic collisions. A pedestrian, if struck by a vehicle driving at 20mph, is likely to suffer slight injuries. At 30mph they will probably be severely hurt; at 40mph or above, they are likely to be killed.

There are, of course, still concerns about the potential negative impacts of a 20mph speed limit – the most frequent being that it would increase congestion.


But that might not actually be true. While travelling at 20mph would obviously take longer than travelling at 30mph on a clear stretch of road, research shows that vehicles flow more smoothly through junctions at slower speeds. This would have a much greater impact in an urban environment, particularly in cities with older road networks.

Some may doubt that 20mph limits can reduce noise and air pollution. A study conducted in Graz, Austria, found that an introduction of 18mph limits back in 1992 led to a noise reduction up to 2.5 dB. Compared to 30mph, 20mph would mean three decibels less traffic noise. There is no conclusive study yet regarding the impact on the environment, but, as a result of reduced acceleration and braking, a 20mph limit may help to reduce fuel consumption and associated emissions.

 Ultimately, the driving issue – forgive the pun – is what impact all this will have on journey times. Plans in Birmingham, much like those elsewhere, still retain some roads at the 30mph or 40mph limit. This should mean most journeys wouldn’t be significantly affected; and, in the case of those urban roads littered with junctions, the improved traffic flow could actually reduce overall journey times.

Still, reducing speed limits will inevitably prompt some motorists to feel penalised. Many will assume it will be a hindrance, even if the evidence says journeys will take the same time at most, be much safer and pleasant for themselves and others, and consume less fuel. The only way to convince critics is by testing 20mph out first and then judging the results.

Luckily, we already have a few case studies to go on.

In the Sherwood area of Nottingham, which has had a full year of 20mph on residential roads, average speeds have gone down by 5.2 per cent. At the same time, casualties in road traffic collisions have decreased from an average of 9.4 per year before implementation, to 8.0 in the year following implementation; most of these were deemed “slight”, rather than severe. In Portsmouth, 20mph limits lowered casualties in road traffic collisions by a further 8 per cent than may have otherwise occurred. In Warrington, collisions in the 20mph speed limit areas fell by a whole 25 per cent; Bristol, Edinburgh, and Dublin have all seen similar results.

Across Europe and the United States, a number of cities have proposed or adopted 20mph or 30 km per hour (about 19mph) limits. New York City has led the way, implementing numerous neighbourhood-scale 20mph zones. Ten other US states also allow for 15 or 20mph limits, mostly in school zones and business districts. They are ubiquitous in the Netherlands, cover 80 per cent of Munich, and a network of 67 European NGOs have pressed the European Union to make 30kmph the normal limit, with 50kmph the exception.

Birmingham is the former centre of Britain’s motor manufacturing industry, something which explains why so much of the city is so geared (sorry) towards cars. As CityMetric editor Jonn Elledge has written in these pages before:

“Outside [the city centre] you quickly run into a world of six-lane highways and traffic jams that snarl up every rush hour because, in large chunks of the city, the only way to get to work is by road.”

So in some ways it seems strange that moves to improve travelling by road have taken so much longer to be proposed here than in other cities where public transport makes them less dependent on roads for daily commutes.

Safer roads, cleaner air, savings on fuel, and less traffic noise would all be welcome changes – and not just in Birmingham. It is one of 16 UK cities the European Commission has issued warnings to our government over due to lethal levels of pollution.

But for the new speed limits are really to affect change, they’ll be dependent on two things. One is motorists obeying the new law; the other is the authorities enforcing it. Time will tell.
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