Thatcham's plans for a 20mph speed limit have been dropped after strong opposition from residents. It's a decision that raises an obvious question: do lower speed limits actually make roads safer, or is 20mph more about local politics than public safety?
Agilysis chairman Dan Campsall joined BBC Radio Berkshire this week to talk through what the evidence actually shows, and where Berkshire sits compared with the rest of the country.
Why 20mph Comes Down to Physics, Not Opinion
A one-tonne car travelling at 30mph carries more than twice the kinetic energy of the same car at 20mph. In a collision involving someone walking or cycling, that difference in energy is often the difference between a serious injury and a fatal one. The human body can only absorb so much force in a crash, and even a small reduction in speed changes what that impact does to it.
That's the case for 20mph limits in places where people live, work, and move around on foot or by bike. It's not about slowing drivers down for its own sake. It's about reducing the energy involved when something goes wrong.
What the Evidence Shows
Wales introduced a default 20mph limit on restricted roads three years ago, and the results are hard to argue with. In the first year alone, an estimated 100 people were spared death or serious injury who might otherwise have been hurt. Beyond the human cost, Dan pointed to the wider economic impact of road trauma on families, employers, and health services.
Other parts of the country have moved in the same direction:
- Scotland has asked every local authority to introduce 20mph limits wherever appropriate.
- Oxfordshire has converted around 73% of its urban road network to 20mph.
According to analysis from Insight Warehouse, Berkshire is behind neighbours like Oxfordshire on 20mph coverage. But it's not starting from nothing. West Berkshire already has more than 90km of 20mph roads in place, and other authorities across the county are extending limits in locations where they judge it appropriate.
Thatcham's scheme may have been scrapped, but the broader direction of travel across Berkshire hasn't changed.
Some evidence suggests that compliance with 20mph limits isn't perfect. Drivers in newly-reduced zones settle closer to 24 or 25mph rather than exactly 20.
Even so, that is still an improvement for safety. Scrubbing speed from 30mph down to 24 or 25mph reduces the energy involved in a crash meaningfully, even without full compliance. And as more areas adopt lower limits, driver behaviour tends to shift with them.
Blanket 20mph limits everywhere isn't the argument being made. The evidence points to something more specific: applying 20mph in the right locations, particularly where people are walking and cycling, saves lives. Thatcham's decision to scrap its scheme reflects local politics as much as road safety evidence, and the two don't always align.
If your authority is weighing up a 20mph scheme, or needs the evidence to evaluate one, get in touch with the Agilysis team.
