It is correct that if you travel at a steady 20 mph then your journey will take 50% longer than at 30 mph.

However, on our roads today it is very rare that you can travel at a constant speed of 30 mph. Bends, blind spots, parked cars, junctions, pedestrian crossings, cars turning right, traffic lights and many more things mean that you have to slow down or stop very often. Indeed, the maximum speed at which you can drive at between obstructions merely increases the time you have to wait at the next obstruction.

Going faster because you have been held up rarely reduces your journey time by any significant amount. Research in Europe where a great deal of 20 mph limits have been implemented found that reducing the maximum speed from 30 mph to 20 mph usually increase a 15 minute journey by just 60 seconds.

Also most places will be within a third of a mile of a 30 mph arterial road. Hence the maximum increase in actual car journey time from introducing 20 mph on the residential roads would be 20 seconds at each end of the journey. In reality this would be far less.

Far from slowing a town to a crawl, 20 mph in residential areas makes hardly any difference at all to journey times.

For further details email rodk@20splentyforus.org.uk or call Rod King on 07973 639781 or Chris Mayes on 0151 706 4464