Fresh analysis of transport data suggests that rising levels of congestion could see average speeds fall from 17mph to 12mph by 2030, resulting in turn in a steep rise in toxic emissions.
In a submission to the Government's consultation on its air quality plans, sustainable transport campaigners Greener Journeys and a former government adviser state that a halving of average city traffic speeds could lead to a 50% increase in emissions from larger vehicles.
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In nose-to-tail traffic, NOx emissions are four times greater than they are in free flow traffic, the report states.
Congestion in the UK’s largest cities is 14% worse than five years ago. Traffic speeds are forecast to fall to an average of 12mph by 2030, while traffic delays are set to almost double over the next decade, leading to an average delay of a minute and a half per mile on England’s A roads.
Greener Journeys and Professor David Begg, the former chairman of the Government’s Commission for Integrated Transport, said it would be impossible to keep air pollution in check unless the Government takes meaningful steps to improve falling urban traffic speeds.
As part of their submission to the Government's heavily criticised air quality plans, they said meaningful steps to tackle urban congestion must be at the heart of the strategy.
They argue that ministers have recognised the link between congestion and pollution, but their plan focuses on removing speed humps and traffic light sequencing rather than reducing the number of vehicles on the road, which causes 75% of all delays.
Claire Haigh, chief executive of Greener Journeys, said: 'It’s time for the Government to take meaningful action to tackle the appalling air quality in our towns and cities. Handing responsibility for all the tough decisions to local authorities will not be sufficient. Government must show leadership.
'Congestion has a direct and severe impact on air pollution. The Government’s plans must tackle congestion and encourage greater use of sustainable transport modes such as the bus, which can take 75 cars off the road reducing both pollution and congestion.'