Many people ask what to do if the average speed on a road is 25mph or above. Can you set a 20mph limit? Lets consider what I call "The 25mph Conundrum".
Setting speed limits based on what drivers think is the right speed is a flawed approach. This is considered in a recent report from NACTO (National Association of City Transportation Officials). It concludes that "Relying on a percentile-based system focused on current driver behavior, rather than a defined safety target to set speed limits, significantly limits cities’ ability to reduce traffic deaths.
So lets go through the logic of solving this conundrum for UK situations.
Jesse Norman MP, the Minister for Transport has written to Councils saying the “WS Atkins report confirms public support for 20mph”. Many Local Authorities are now reviewing 20mph policies and re-interpreting DfT guidance.Read more
Today the government published its long awaited report evaluating 20mph limit implementations. We welcome the report. It has been a long time coming since 2014 when it was commissioned.
And in that time there have been nearly half a million casualties on streets with a 30mph limit.
The report only evaluated a small number of case studies which in themselves only covered part of an authority. There are some useful indicators in the report, particularly around the negative aspects of police failing to routinely enforce 20mph limits and the need for national engagement and awareness on the benefits of reducing speeds below 30mph in residential and other roads.
However, we have major reservations about the primary data used in the report around speed reductions and the complete failure of the study to look at sufficient casualty figures to be able to draw any conclusions that would be statistically credible. These were key reasons for the commissioning of the report and we are amazed at the choice of data measured which appears to be based on measuring what is available rather than what is meaningful.Read more
Far from having a “national” urban speed limit of 30mph, this has been rejected by local authorities for a quarter of the UK population. All but two Inner London Boroughs and over half of the UK’s largest urban authorities now have a 20mph limit for most roads. Rather than just “recommending” 20mph limits the government should set a national 20mph limit and permit local authorities to justify any higher limits.Read more
Signing 20mph speed limits has become easier and dramatically cheaper. Repeater signs are now optional. Half the terminal (start/end of limit) signs are required. A minimally signed scheme stipulates 70% fewer capital items. Total costs fall by 40%. Cost per head falls from £2.50 to £1.50Read more