20mph speed limits for Wales

If you’re driving in Wales, from today you’ll the speed limit has changed from 30mph to 20mph by default on ‘restricted roads’. It doesn’t affect all 30mph roads. Restricted roads are usually residential or busy pedestrian streets with streetlights.

Wales has made this decision with the aim of saving lives, reducing collisions and reducing injuries. The estimates are 40% fewer collisions, 6-10 lives saved and 1200-2000 people avoiding injury. The change is also designed to make streets safer for pedestrians, reduce noise pollution (from engines and road noise) and encourage more people to walk and cycle.

Research showed that a reduction in average speed by 1mph resulted in a decrease in the average number of collisions by 6%.

For petrol and diesel vehicles, it may increase fuel consumption and therefore potentially have a negative effect on air quality. However, many other factors influence fuel economy. For electric vehicles, there will be very little change as the optimum speed for an EV is around 25mph.

Changing the speed limit cost around £32 million in terms of legislative costs, changing signage and road markings, administration, and publicity. This does not include an estimate for lost time due to increases in journey time. However, estimates are that the health benefits could be as much as £92 million per year.

Enforcement will be a mixture of education for those drivers just over the limit, and then fines and points for drivers exceeding the limit by a substantial margin.

There are a few things that remain to be seen:

Will a 20mph speed limit impede emergency service vehicles? It’s possible, but generally, drivers get out of the way. There will be a change in the speed differential between an emergency services vehicle that can legally exceed the speed limit, and drivers who are driving at 20mph. For oncoming vehicles, they are travelling 10mph slower – that means less risk. For vehicles travelling in the same direction, the emergency services vehicle will have a faster closing speed by 10mph – that may catch some people out; emergency service vehicle drivers may find themselves having to brake more and that will increase wear and tear on brakes and worsen fuel economy.

Will more people choose to walk and cycle? This is an aim, but there is not much evidence that just because vehicles drive more slowly, people change their habits. Parents may feel it’s safer for their kids to bike or walk to school.