In its report, the IAM said that its analysis of government data has found that the number of serious accidents on 20mph roads has increased by over a quarter (26%) last year. Slight accidents on 20mph roads increased by 17%.
In the same year, there was a decrease in the number of serious and slight accidents on 30mph roads and 40 mph roads. Serious accidents went down 9% on 30mph roads and 7% on 40 mph roads. There was a 5% reduction in slight accidents on 30 mph roads and a 3% decrease on 40mph roads.
In response, 20's Plenty for Us – a “not for profit” organisation that campaigns for 20mph to become the default speed limit on residential and urban streets – has claimed that the IAM’s conclusions show ‘a woeful lack of understanding of statistics’.
The organisation said the reason why casualties on 20mph roads have increased is mainly because many UK towns and cities are changing the limit on roads from 30mph to 20mph. As a result the total length of 20mph roads is increasing and 30mph decreasing.
The organisation said: ‘It therefore comes as no surprise to find that the total casualties on 20mph roads has increased (by 20%) in 2013 and decreased on 30mph roads (by 7%). In fact with 20% of the UK now in local authorities currently making most roads 20mph this is entirely expected. DfT record no statistics on the total length of 20mph or 30mph roads and hence any conclusion that this increase reflects any increased danger would not have any foundation.’
The organisation added its view that one valid statistic that can be gleaned from the 2013 casualty figures is the risk of death for casualties in 20mph and 30mph roads. On 20mph roads in 2013 there were 6 deaths out of 3,164 casualties (0.2%) whilst on 30mph roads there were 538 deaths out of 111,186 casualties (0.5%). It added its view that therefore on a 30mph road any casualty is 2.5 times more likely to result in a fatality than on a 20mph road.
Rod King, founder and campaign director of 20’s Plenty for Us, commented: ‘We are amazed and disappointed that the Institute of Advanced Motorists should make such a woeful mistake in their conclusions from the DfT statistics. In fact, wherever 20mph limits have been piloted, on looking at the casualties in detail, councils have concluded that there was a positive effect on road safety and subsequently widened the implementation across most areas. Now 20% of the UK population live in towns, cities or villages where the Traffic Authority is convinced that 20 is plenty for most streets. The IAM conclusion is bogus and reflects a poor understanding of either the changing numbers and success of 20mph limits or basic statistics.’
