20mph will increase air pollution according to a report
Commenting on a Newport City Council report that the switch to 20mph speed limits in Wales could end up increasing air pollution levels in some parts of Newport, Welsh Conservatives Shadow Transport Minister, Natasha Asghar MS said:
“As time goes on it is becoming clearer that Labour’s arguments for 20mph speed limits are falling apart around them.
“With Labour’s forthcoming Environment (Air Quality and Soundscapes) (Wales) Bill looking to combat poor air quality, this report should give them pause for thought about introducing further speed limit reductions.
“The evidence is mounting against Labour’s calamitous 20mph policy which clearly does not do what it is claimed to, with Spanish safety figures showing an increase in road deaths whilst fatalities have also increased in 20mph zones across Bath. Labour must finally admit defeat and scrap this costly harmful policy.”
Taken from ROSPA 20mph Zones and Speed Limits Factsheet
Research that investigates the effects on non-road safety related public health outcomes, such as pollution, is limited. It is possible that 20mph zones and limits could actually increase pollution, as some vehicles will operate inefficiently at low speeds.
Local Highway Authorities should consider the type of traffic calming measure used within 20mph zones, as some features can cause more vehicle pollution than others. This is illustrated in a report published by Imperial College London which explored the effects of a London 20mph speed restriction on vehicle emissions.
It was found that cars can produce up to 98% more nitrogen oxides and up to 64% more carbon dioxide when driving over a speed bump as opposed to a speed cushion (these are shallower and do not span the entire width of the road).
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