The current transport minister, Gavin Strang, is widely predicted to be for the chop at the next reshuffle.

ECONOMIST: Driving Britain off the roads

He added that 70% of the current planned transport spending programme will be invested in public transport, helping to cut the number of single car journeys.

BBC: NEWS | UK | Scotland | Public have say on climate change

Despite the Treasury's long record of being opposed to hypothecation, ministers may come to regard this as the best course if the current debate over transport taxation continues at a high pitch.

ECONOMIST: Fuel duties