It’s three months since Wales adopted a default 20mph speed limit in previously 30mph limits, and early findings indicate that average speeds have reduced since, though we don’t yet know what the effect on casualties will be.

Although not a blanket speed limit (local authorities are free to retain the 30-limit if they think that 20mph is too slow) the 20-limit has affected many stretches of road. An independent report by Agilysys and TomTom has studied traffic speeds on 310 miles of roads in 10 town and city areas which have seen a reduction in the speed limit to 20mph. The results should be treated with caution as rather than measure the average of all traffic, the analysts tracked the speed of particular vehicles which could upload speed and location data to TomTom’s servers.

Under the previous 30mph limit, average speed on the measured stretches of road was 22.7mph, which fell to 19.8mph immediately after the introduction of the 20-limits. Three months on that has increased slightly to 20.3mph, which equates to a drop of around 10% compared to the previous 30-limits. Safety research indicates that quite small reductions in average speed can have a larger effect on casualties, with the Global Road Safety Research Facility finding that a 3mph reduction would result in 32% fewer casualties and 25% fewer serious injuries. Casualty figures for Wales aren’t available yet, so watch this space.

BMF Chair Jim Freeman said: “Judging from the comments on social media, and elsewhere, the 20 limit is about as popular as Covid. Looking at the different average speeds, before and after the 20 limit was introduced, what on earth was the point? The ‘20’s Plenty’ enthusiasts may argue that every reduction of just one MPH makes a big difference to the casualty stats. I’ve got news for them, banning all travel would reduce casualties even more, but if you ask anybody whether they think that’s a worthwhile bargain, be prepared for some offensive language!”

Written by Peter Henshaw

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