As a witness of Vancouver's 2010 Winter-Olympic games, I can guarantee that the crowds in London for the summer games are going to be HUGE. It was a nightmare travelling along the new Canada Line from Downtown towards Vancouver Airport - but I know that it would have been a lot worse without that new line.
Currently, the Crossrail idea is meeting controversy because it cuts right beneath central london, was proposed decades ago, and many key venues are being lost to the development. The Canada Line met similar controversy, because TransLink (the regional transport authority) decided to use "Cut and Cover" as opposed to boring the tunnels, because it would save money. It caused traffic problems all along Cambie Street for the four years it was under construction.
London's Crossrail project is destined to open to the public in 2017 - 5 years after the Olympic Games. Far too late to be of any use for Olympic visitors. I believe that in order to give London any hope of avoiding absolute gridlock status, the tunnels from Paddington to Stratford should be the first things constructed, and opened to the public BY July 2012. The lines from Shenfield and Heathrow Airport are already there... just get the tunnels built!
If the tunnels are not open by July 2012, all hell is going to be on the loose in Central London...
