These first details of the mayor's authority and the role of the new London assembly will emerge this week in a government White Paper.
Under the proposals the mayor will preside over a single transport authority for London. The mayor, who will chair the authority, will set out a transport strategy, influence priorities and shift resources in the network.
However the mayor will not be given revenue raising powers, which will stay with the London boroughs, and subsidy for London's transport network will come from the Department of the Environment, Transport and the Regions.
That will disappoint those who are considering standing for the post next year, if plans win assent in a referendum in May.
Most observers believe that the mayor's greatest influence will be through the media, as a politician with a personal mandate to speak for the city.
He or she will also have responsibility for tourist promotion, including an annual budget of pounds 1.5m, and the ability to create an overall environmental plan for the capital.
That power can force the London boroughs to fit into proposals, such as those designed to combat air pollution.
Other functions include a consultative role when the Home Secretary appoints the Metropolitan Police Commissioner.
The new assembly will be designed to be a counter-weight to the mayor. Ministers expect the mayor and the assembly to employ no more than 300 people.
The White Paper will also confirm that the Government does not intend to use a first-past-the-post electoral system for the post of mayor and for elections to the Greater London assembly.
Elections both for mayor and the assembly will have a proportional element, probably using the Alternative Vote system.
Under AV, if no candidate gets more than 50 per cent of the vote, the second preferences of the last candidate are redistributed.