Editorial: The logic of 20mph speed limits

That more than a third of local authorities have either already instituted a 20mph speed limit on some residential roads, or have plans to do so, can only be applauded. And with public support for more stringent restrictions in built-up areas now running at more than 60 per cent, as reported by this newspaper this week, it can only be hoped that 20mph will soon become the new normal.

The most compelling argument is, of course, the question of safety. Not only do drivers travelling at slower speeds have more time to react. The damage inflicted by hitting a pedestrian at 20mph, as opposed to 30mph, is also markedly reduced. Indeed, the human skull's ability to withstand impact drops sharply beyond 20mph, perhaps because that is our own top speed.

Statistics on accidents point the same way. More than half of deaths and injuries occur in 30mph zones, so the effect of a blanket 20mph limit in residential areas would be far from marginal. It might also help shift Britain from the top spot in the European league for pedestrian fatalities. Indeed, with the most recent figures showing sharp rises in accidents involving pedestrians and cyclists (up by 5 per cent and 9 per cent respectively), it is difficult to argue convincingly in defence of the status quo.

Safety is, however, not the only consideration here. There are also broader environmental benefits. Motorists' reservations might be shaken, for example, when they consider that traffic is more likely to keep flowing if cars maintain a steady (albeit more leisurely) pace, rather than moving faster but braking more often. Pollution – both noise and particulate – also noticeably decrease at slower speeds.

There is a downside, of course: journeys may take slightly longer. But it is a matter of less than a minute, on the average urban journey, when congestion, traffic lights and so on are taken into account. Set against the trauma of broken bodies and ruined lives, a few seconds longer in the car is surely a price worth paying?