Councillor Phil Jones, Camden Council’s Cabinet Member for Sustainability, outlines his borough’s move towards a 20mph borough-wide speed limit in this article from the latest edition of New Ground, the transport special.

It is 22 years since the first 20mph zones were introduced in residential areas in the UK to guard against speeding traffic and create more pleasant places to live. But now more and more communities, councillors and campaigners are asking whether a more comprehensive shift to slower speeds can not only reduce road accidents, but also contribute to a more sustainable transport system and better quality of life.

In Camden, north London, we are moving towards a 20mph borough-wide speed limit including on the main roads where most accidents happen. Greater safety is the goal but we also want to reduce traffic domination on our congested, polluted roads, improve our public spaces and encourage more people to walk and cycle.

It is not just Camden that is moving forward on this agenda. Labour councils in Liverpool and Islington are implementing comprehensive shifts to 20mph. London boroughs including Southwark and Hackney are actively exploring extension of 20mph to main roads. Growing numbers of councillors believe that safe speeds should not just be for quiet residential zones or for outside schools. Instead, we want a bolder ‘total 20’ approach of a default 20mph across a whole local authority area.

The simple fact is that most accidents occur on main roads rather than on side streets. More than half of road deaths and serious injuries occur on roads with 30 mph limits. So making further reductions in casualty levels needs to focus on these places. Drivers may have got used to driving at 30mph but this is faster than the norm in many cities and towns in other parts of northern Europe. `Slowing down doesn’t even add significantly to journey times as most delay is caused by stopping at traffic lights and congestion points rather than by the driving speed.

Slower speeds mean fewer casualties. According to the Royal Society for the Prevention of Accidents (ROSPA), a pedestrian hit at 20mph has a 2.5 per cent chance of death compared to a 20 per cent chance at 30mph. Of course, it would be naïve to assume that all motorists will suddenly slow to 20mph as soon as a council decides they should. But that is not necessary to achieve fewer casualties. The DfT estimates that for every 1mph reduction in speeds, a 6% reduction in accidents results. So, even a couple of miles slower on average means a lot of families spared considerable pain and distress. Not to mention the significant cost to the NHS of treating the victim and the wider impact on the economy – road accidents cost the country £15.5bn per year.

Any serious road accident is a tragedy for the victim and their friends and family, but some groups are more likely to suffer than others. Children living in deprived areas and some ethnic minorities are more likely to travel as pedestrians and are therefore at greater risk of injury from road accidents. So improving road safety through adopting 20mph is also about fairness and equality, and Labour councils have a responsibility to consider it in those terms.

Introducing road humps where they are not wanted can cause enough local controversy to strike fear into the heart of even the most road safety-conscious councillor. But traffic calming measures are not needed to establish a 20mph speed limit. Evidence demonstrates that using signage and road markings alone will bring reductions in speeds. In Camden, a 20mph zone implemented in Belsize without significant traffic calming brought an average reduction in speed of 2.3 mph. On Camden High Street, one of the only ‘red routes’ in London with a 20mph limit, we also saw falls in the number of cars travelling at over 20mph after the restriction was implemented.

Another area where the pro-car lobby like to challenge 20mph limits is over enforcement. It is suggested that the move is pointless unless the police are lined up with cameras to catch and punish drivers who stray over the limit. The fact that the police don’t generally enforce speed limits at 30mph is ignored. However, you don’t necessarily need police enforcement to encourage drivers to slow down – simply introducing the new limit has an effect. So while it makes sense to encourage the police to enforce 20mph where there is a proven speed problem, as they have begun to do for example in Oxford, the confusing position of some police forces that they will not enforce 20mph limits unless they are self-enforcing, should not be a barrier.

As well as a way of avoiding unnecessary road deaths, shifting to 20mph is also about encouraging sustainable transport like walking and cycling that help us reduce carbon emissions. In Camden we have reduced car journeys and increased levels of cycling, but we still suffer from road traffic pollution that is so severe that it contributes to thousands of deaths in London each year.

The biggest barrier to encouraging more people to take up urban cycling is fear of the busy main roads where too many cyclists are still knocked down. Fixing dangerous junctions and providing safe routes is part of the answer, but slowing the traffic is crucial. Pedestrian groups also back the change as part of a shirt to putting people before cars. Slower traffic gives greater confidence to vulnerable pedestrians when crossing the road and the evidence from other parts of Europe is that slower vehicle speeds are associated with higher levels of walking.

But what about air quality? Doesn’t 20mph simply increase fuel consumption and therefore pollution? There is negligible evidence of this. Fuel efficiency and emissions are influenced more by levels of accelerating and braking than by vehicle speed. And there are far more important factors in determining levels of pollution from transport, such as type of vehicle, the fuel used, and volume of traffic. If a 20mph limit encourages more people to walk and cycle rather than drive then the impact on pollution levels can only be positive.

‘Total 20’ is first and foremost about reducing road casualties. However, it is also about encouraging a shift to sustainable transport, reducing the harmful emissions that damage the environment, and recognising that our streets are not just routes for motorists but also public spaces used by all. It is a popular and evidence based policy, and its time has come.

Cllr Phil Jones is Cabinet Member for Sustainability at the London Borough of Camden. He tweets @philjones79