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One month on: Do 20mph speed limits work?

By Mathilda Bartholomew | October 27, 2023

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A recent study by an independent transport data consultancy reveals that the implementation of 20mph speed limits on Welsh roads has resulted in only a marginal decrease of 2.3mph in average speeds.

One month on: Do 20mph speed limits work?

According to recent sample data, the majority of drivers in Wales are adhering to the newly implemented 20mph speed limit on various roads. However, there seems to be a modest rebound in speeds after an initial sharp decline following the introduction of the new default limit.

Independent transport consultants Agilysis revisited two sample routes in Cardiff and Wrexham a month later, discovering a 2.3mph decrease in speeds. This contrasts with a more significant 3.1mph drop observed in the first week of the limit's enforcement. The analysis, based on TomTom data from approximately 10,000 vehicle movements along B4487 Newport Road in Cardiff and A5152 Chester Road in Wrexham, provides insights into the driving behavior.

In comparison, the original research covered nearly 30 million vehicle movements in Wales during the week following the implementation of the new limit on September 17. It revealed that the top 15% of fastest drivers experienced a 4.9mph reduction in the first week, which tapered to a 3.8mph decrease in the subsequent week.

Richard Owen, the CEO of Agilysis and the report's author, cautioned against complacency, emphasising concerns about a minority of drivers not adjusting their speed appropriately. Owen suggested that identifying roads with lower compliance levels could be crucial for targeted education and enforcement efforts.

Official figures on vehicle speeds are anticipated in spring 2024, while updated data from pilot areas is expected later this year. The 20mph limit has faced opposition, with the Welsh Conservatives expressing support for the limit near schools, hospitals, and care homes but criticising the "disastrous" and "ludicrous" blanket rollout. In contrast, the Welsh government contends that the impact on journey time will be minimal and enjoys support from various organizations, including Friends of the Earth Cymru, Action for Children, and Sustrans Cymru.

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