A Commons inquiry into road tolls has been called ahead of the publication of a major government announcement on transport strategy.
Would a new toll road be better than widening the M6?
It comes after the government said it would back a second toll road linking Birmingham and Manchester along the M6.
On Tuesday, Transport Secretary Alistair Darling will lay out short and medium term policy, including a vision for the next 30 years.
He will also give the go-ahead for a £10bn cross-London railway scheme.
The Commons Transport Committee will look at the impact the country's first toll motorway linking Staffordshire and Warwickshire - also along the M6 - has had on congestion and traffic levels.
Pay as you go
The committee, chaired by Labour MP Gwyneth Dunwoody, will ask whether extending the scheme with a new 50-mile toll road would be more cost-effective than simply widening the existing motorway and look at its potential environmental impact.
It comes as Mr Darling is set to outline the government's review of its 10-year transport strategy, setting policies for the next five years and outlines its longer-term vision.
This may include proposing an extension of congestion charging, pioneered in London and Durham, to other cities.
He is also expected to give the go-ahead for the Crossrail scheme, which will link Kingston, Richmond and Heathrow in south and west London with Shenfield and Ebbsfleet east of the capital.
More congestion charging?
Crossrail, which would be a mainly privately-funded mainline service would also link key Tube stations such as Bond Street, Tottenham Court Road and Liverpool Street.
The scheme, which would run through tunnels beneath central London, would not be completed before around 2013 - missing the proposed 2012 Olympics in the capital.
Mr Darling will also have to respond to an independent report on the feasibility of nationwide road tolls. which is also due to be published on Tuesday.
Its findings could include a suggestion that local authorities be allowed to cut council tax in return for introducing congestion charge schemes.
It may also include a recommendation that charging be introduced for new lanes on widened motorways.
It comes after the Institute of Public Policy Research think tank suggested that road tolls could be used to raise £16bn a year, allowing road tax to be scrapped.