Speed bumps could be removed from the nation’s roads as part of the Government’s plans to cut pollution.
Other traffic-calming measures could also be removed to prevent cars repeatedly slowing down and speeding up, which almost doubles the amount of harmful gases they pump out.
Councils will be advised to take measures to improve the flow of traffic as part of a new clean air strategy to be unveiled later this month.
Motoring organisations have urged ministers to cut pollution by reducing traffic jams and encouraging drivers to go at a steady speed rather than punishing them with stealth taxes.
Up to 10 million drivers of older diesel vehicles are expected to be told that they will have to pay fees of up to £20 per day to drive in some urban areas under the so-called “toxin tax”.
That has prompted fury from drivers who were encouraged to buy diesels by the last Labour government, which Labour MPs have since admitted was a huge mistake.
The Government has been forced to reconsider its proposals for improving air quality after the High Court ruled last year that its existing strategy did not meet legal requirements.
The Department for the Environment, Food and Rural Affairs (Defra) and the Department for Transport must now present a joint new plan to the court on April 24.
Ministers have come up with a raft of new ideas, which will include advice to local councils on how to keep traffic flowing steadily, rather than stop-start driving, which increases the amount of fuel vehicles burn.
Research by Imperial College London found that driving over speed bumps in a diesel car produces 98 per cent more nitrogen dioxide than driving over road cushions.
Speed bumps, which are steeper and go across the whole road, force drivers to slow right down to avoid damaging their car, whereas cushions, while are normally placed in groups of two or three across the road and have a far shallower slope, require less deceleration.
Other options which are expected to be put forward include better sequencing of traffic lights to ensure that drivers will keep arriving at green lights rather than red ones if they drive within the speed limit.
The proposals are not, however, expected to include a scrappage scheme for older diesels.
Whitehall sources have said that discussions are still taking place about the possibility of a scrappage scheme, but it is unlikely to be addressed until the autumn budget, at the earliest.
The AA is putting pressure on the Government to pay drivers of older diesels a scrappage fee to encourage them to switch to newer, cleaner vehicles, arguing that pollution taxes “totally miss the point”.
It says the worst polluters tend to be older buses, lorries, taxis and badly maintained cars. Edmund King, the President of the AA, said: “Government and local authorities need to deal with air quality issues in a sensitive and scientific manner rather than just demonising all diesels.
“We are encouraging Government to introduce a targeted scrappage scheme in urban areas to encourage the faster replacement of older buses, trucks, taxis and other gross polluting vehicles.”
Last week Theresa May hinted that drivers of diesel cars could be given financial help because Labour introduced tax breaks for diesel cars in 2001 to encourage drivers to buy them.
It subsequently emerged that diesel vehicles produce four times more nitrogen dioxide and 22 times more particulates than petrol cars.
Mrs May said she was “very conscious” of the fact that there was a push towards diesel under Labour and said Government policies need to “take [that] into account”.
The High Court case that forced the current re-think was brought by the environmental campaign group ClientEarth, which says car manufacturers should be forced to pay for recalling and upgrading polluting diesel cars.