Wales’ 20mph speed limit did not improve air quality, study finds

21 comments

1. Was the 20mph speed limit introduced specifically to improve air quality?

2. Who gives a fuck about this? It makes cities and towns more safe for pedestrians. It’s been absolutely fine in Scotland.

3. 20mph limits reduce the number of deaths from collisions. Take a breath, slow down, you’ll get to your destination soon enough.

4. We all know this! 20 mph limits are about control not air quality!

5. makes it easier to stop a 2000kg plus electric car

6. Well often 20mph requires a lower gear and higher engine speed than 30mph so this is not at all surprising.

7. https://www.swansea.gov.uk/article/20765/Introduction-of-20mph-speed-limit

   > Evidence shows that lower speeds result in fewer collisions and a reduced severity of injuries.

   > Pedestrians are five times more likely to be killed if hit by a vehicle driven at 30mph compared to 20mph.

   > As well as the safety benefits, 20mph zones improve air quality, reduce noise pollution and can result in healthier lifestyles by encouraging more walking and cycling in communities. Roads will be safer and shared more equally between different road users.

   So their primary motivation seems to be to reduce collisions and severity of injuries. Air quality seems to be the side benefit they claim.

   If air quality isn’t improving, it would be interesting to see the statistics on number of collisions and severity of injuries.

8. Every single time I’ve hit a 20mph zone, no one has done 20mph lol

9. I assume the Torygraph will soon be publishing reports stating that the Rwanda policy hasn’t improved sheep farming productivity?

   If we’re just making up measures to measure policies by, whether or not they are the reason they were introduced that is.

10. Well of course you’re having cars spend twice the time on the road!

11. Considering that was never one of the goals (and OP’s attempts to claim it was are laughable), this is an interesting angle for the Telegraph to take. The readership will lap it up of course, but I suspect most non-readers first reaction will be “ok, but that wasn’t the point?”

12. Ignoring the fact that air quality was not the driving reason for implementing 20 zones, it’s also massively disingenuous to imply that air quality = NOx emmisions. Non-exhaust particulate emmisions like tyre and brake wear will decrease with lower speeds due to less friction and abrasion

13. 20 zones in London are nothing but a cash grab. They are made to punish drivers. Residential and schools I understand but on main roads with this average speech check is a huge negative.

14. I honestly dont care about the environmental impact one way or the other, everyone will be moving to electric vehicles in the next 10-15 years anyway, so it just doesnt matter

    What does matter is the insane way they implemented it

    The goal of having the majority of residential streets be 20 other than trunk roads is a very good one. No doubt about it

    However changing the default from 30 to 20 in order to save money by putting up less signs has been a disaster. Most side streets end at a 30 trunk road anyway so they had to still put up the same, if not more due to repeaters on the trunk roads.

    It has left the roads in a state where you can be on what is probably a 30, there will be sporadic signage for 30, some 40’s written/faded on the road surface, but it is actually a twenty. People have started straight up ignoring the speed limits in these raods as they have no idea what they are

    They should have left it as it was and put up twenty signs in the few residential areas that werent already done.

    They have put up thirty signs as you approach a roundabout by me. The intention is that the other 3 roads coming off the roundabout are 30’s so they put up one sign

    Legally it means the roundabout is 30 and the first 200 yards till you hit a repeater on the three side streets are 20 then 30

    Its insane, they eroded what a traffic sign even means.

    They should reverse the built up areas 20 back to 30 and put up twenty signs where needed

15. No way! The Jellygraph with an article criticising low speed limits. Britain’s worst newspaper.

16. The main goal was always safety, air quality was a side benefit at best, much of Wales already has very clean air due to low population density.

    Telegraph as usual can’t help itself to demonise anything even remotely progressive.

17. Why not introduce a carbon tax like trudeau’s government to screw over the welsh some more

18. I don’t understand why anyone thought it would? You have an efficiency curve for cars that peek about 50mph, where it gets its maximum mpg, anything under 30 drops the mpg drastically, meaning more pollution per mile;

    So when you lower the speed to 20mph you are saving some number of accidents at the cost of extra pollution, which itself has a health cost. That’s why these decisions need to be made based on each bit of road, considering use and history; not indiscriminately, which is what the Welsh experiment did.

19. Obviously need to see the actual study, but the first obvious question is: Do a significant number of cars actually change their speed between the two sets of sensors?

20. Why would it have, you’re in a lower gear you’re burning more fuel, creating more C02 and particulate content entering the atmos , the engine isn’t working as efferently as it would.

    If anything in those area the air quality will drop.

    But rules aren’t usually made by intelligent people so no surprise there.

21. Probably because they aren’t enforcing it and everyone is driving at 30 on any road suitable anyway!