Government Air Quality Plan under threat from Congestion Crisis

Greener Journeys
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  • Average traffic speeds in UK’s busiest cities will fall from 17mph to 12mph by 2030 as road delays double
  • Halving average city traffic speed equal to 50% increase in emissions from larger vehicles
  • Diesel cars are responsible for the largest share (41%) of NOx emissions from road transport

The Government’s plan to improve air quality will fail because it ignores the growing impact of congestion on pollution in city centres, transport experts warn today.

New analysis of transport data reveals the direct impact of rising congestion on harmful NOx emissions, with a halving of average city traffic speeds leading to a 50% increase in emissions from larger vehicles as they crawl along busy urban roads. In nose-to-tail traffic, NOx emissions are four times greater than they are in free flow traffic.

In contrast, easing traffic flow can lead to dramatic reductions in NOx emissions from all vehicle types. Emissions from the latest Euro VI diesel buses, for example, can be halved by increasing speeds from just 3.7mph to 5mph.

Diesel cars are the single biggest contributor to NOx emissions on the road, accounting for 41% of all emissions from road transport. A journey by a modern Euro 6 diesel car emits 10 times more NOx per passenger than a comparable journey by a Euro VI bus.

The analysis by Greener Journeys, the sustainable transport campaign, and Professor David Begg, the former Chairman of the Government’s Commission for Integrated Transport, is published on National Clean Air Day, in Greener Journeys’ official submission to the Government’s consultation on its draft Air Quality Plan, which ends today.

It will be impossible to keep air pollution in check unless the Government takes meaningful steps to improve falling urban traffic speeds, they warned.

Congestion in the UK’s largest cities is 14% worse than five years ago and traffic speeds are forecast to fall by almost 5mph from 17mph to an average of 12mph by 2030, and significantly slower in peak hours.

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.

If the Government is serious about addressing the growing public health emergency caused by air pollution, it must take meaningful steps to tackle urban congestion at the heart of the strategy, the submission says.

Air pollution causes up to 50,000 early deaths a year in the UK, and the World Health Organisation has calculated that people in the UK are 64 times more likely to die from air pollution as those in Sweden, and twice as likely as those in the USA.

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.

The only way to truly resolve the air quality crisis is to reduce vehicle numbers and free up alternative forms of transport such as buses. This includes extending the scope of Clean Air Zones to include diesel cars, and encouraging more people to use public transport such as buses instead of driving. The latest Euro VI buses are 95% cleaner than previous models.

The draft Air Quality Plan acknowledges that without further action, 31 of 43 UK zones will miss air quality targets in 2020. Current plans, however, identify buses and taxis as priority diesels to target within clean air zones, followed by HGVs and vans, with cars a drastic final option – the reverse order of the contribution these vehicles make to NOx emissions totals.

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.

“Some measures in the Air Quality Plan, such as the Government’s commitment to retrofit technology are promising. However, its failure to take tougher action on diesel cars and establish further mandatory Clean Air Zones exposes a lack of commitment to tackling air quality.

“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.”

Professor David Begg, Chief Executive of Transport Times and former Chairman of the Government’s Commission for Integrated Transport, said:

“The Government’s current plans fall short of what is needed to tackle air pollution. Policies should focus on easing congestion, increasing support for upgrading public transport such as buses, and more action to crack down on the biggest polluters on the road – diesel cars.

“The congestion problem is not going to go away on its own. The growth in online shopping means the proportion of vans on the road continues to increase, and unlike cars these vehicles don’t simply go away when traffic jams get too severe. Unless action is taken, urban traffic speeds will continue to fall until they reach walking pace.”

For further information

Greener Journeys Press Office or +44 (0)20 3128 8555

About Greener Journeys

Greener Journeys is a campaign dedicated to encouraging people to make more sustainable travel choices. It is a coalition of the UK’s leading public transport organizations, user groups and supporters. It aims to reduce CO2 emissions from transport by encouraging people to switch some of their car journeys to bus or coach instead. Switching from car to bus for just one journey a month would mean one billion fewer car journeys on our roads and would save 2 million tonnes of CO2 every year. For more information visit

Projected average Traffic speeds (mph) on local A roads English cities:[1]

City                                     2016                                2030

City of London                     6.9                             5

London (Camden)              8.4                             6

Bristol                                       15.3                          11

Manchester                            15.7                          11.3

Greater London                   16.3                          11.7

Brighton                                  16.7                          12

Hull                                             16.8                          12.1

Nottingham                           16.9                          12.2

Liverpool                                 17.5                          12.6

Southampton                       17.5                          12.6

Birmingham                          18.6                          13.4

Newcastle                               19.4                          14

Derby                                         20.9                          15.3

Leeds                                          23.6                          17

[1] Analysis based on data supplied in “Average speeds by region” Department for Transport (2016)

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