Economy of London project is construction of 42 km (26 mi) of new tunnels connecting stations in central London including a branch to Canary Wharf in east London. It is Europe's biggest construction project with a £15 billion projected cost. An additional line, Crossrail 2, has been proposed. London is served by six international airports which are the world's busiest city airport system by passenger traffic. These are Heathrow, Gatwick, Stansted, Luton, London City, and Southend. There are a number of proposals for expanding airport capacity for London including expansion of London Heathrow Airport and expansion of Gatwick Airport. The principal argument in
London Stansted Airport until Braintree. The road distance to London is . As of October 1996, the airport has 2,500 short stay parking spaces within walking distance to the terminal. In addition, as of the same month, the airport has over 8,000 long stay spaces located near the M11 motorway and A120 junction. A courtesy bus service links the long stay spaces to the terminal. The airport also offers mid stay parking, closer to the terminal than its long stay spaces."" Stansted Airport also offers valet-parking and a meet and greet service which is similar to valet but marketed more at the leisure