Uni Study Finds 20mph Zones Make Little Difference to Air Quality

The rush to establish a default 20mph lmit across most of urban Britain is popular with Councils, who see it as an easy way to generate more traffic fine revenue, from fixed and mobile cameras. But does it make the roads and local areas feel more fresher in terms of air pollution? Does a 20mph limit actually reduce collisions? Hmm, maybe, seems to be the conclusion.

The latest study looked at data from 2016 onwards in Belfast, selecting various city centre streets. Regarding speed reduction, there was little evidence to support drivers slowed down in general. Ditto on accidents, patchy data on air quality too. The QUB report is here.

One argument repeatedly put forward by middle class people seeking to increase property values with LTNs is that it fights air pollution. It may do, in their street, but bollards and planters generally send vehicle traffic to arterial roads, where poorer people often live in apartments.


You could argue that even a 10mph speed limit would do little to prevent the one million uninsured and untaxed drivers from doing what they please on UK roads, plus the Police have little time to seize and crush the cars, then process the offenders via the justice system. The roll out of ULEZ zones may well see more vehicles on cloned or obscured plates as they seek to avoid paying a fee simply to pop to Tesco. More research on the links between risky behaviour like not taxing/insuring cars, not holding a licence, and the number of collisions those illegal drivers have per mile, compared to legal drivers, might be useful. But it is unlikely to be funded, since it has nothing to do with climate change.

The tendency younger males have to race their cars at weekends is also another feature that is unlikely to be affected by lowering speed limits. Stopping that activity requires physical Police operations, which are expensive to maintain.


One fact that nobody can dispute is that fatalities on UK roads are at their lowest ever level (except for 2020 lockdown year) so a mix of car tech like airbags, cameras, collision avoidance and lane alerts etc. plus choked urban roads, potholes, speed bumps, LTN obstacles and lowering speed limits all plays a part.

IE feels that the roll out of more in-car assisted driver tech will keep on reducing collisions. Plus the government and local Councils deliberate policy of neglecting roads maintenance will also help reduce speeds. As public transport is an unreliable mess, expect more people to choose SUV type hybrid cars, rather than buses, trams or trains. Pure EVs will fail to catch on as people fear power cuts, rationing of chargepoint supply in the name of climate lockdowns and the introduction of VED tax.

It’s all good news for brokers and insurers looking to offer cover on vehicles.

RAC Comment

Following a report from Queen’s University Belfast into the effectiveness of 20mph speed limits, RAC road safety spokesman Simon Williams said:

“The findings of this study are surprising as they appear to suggest that drivers on 20mph roads in Belfast hardly slowed down at all, despite the lower speed limit, which is at odds with other reports. It seems there is a serious problem with compliance as we would expect that even without enforcement average speeds would drop. Consequently, the study may demonstrate a need for councils to find other ways to get drivers to slow down, whether that’s through enforcement or modifying road design with traffic islands, well-designed speed humps or chicanes.

“It’s also important that 20mph limits are used in places where they stand to make the biggest positive impact, such as in built-up areas and in locations where there are large volumes of motorised traffic, cyclists and pedestrians – but clearly that depends on a meaningful drop in overall vehicle speeds. Equally, our research shows drivers are less likely to comply with a lower limit if they don’t believe it’s appropriate for the type of road.”

About alastair walker 10924 Articles
20 years experience as a journalist and magazine editor. I'm your contact for press releases, events, news and commercial opportunities at Insurance-Edge.Net

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