Organisers are promising a "strong line-up" that will include "some of the very best riders" in the world, but say names won't be confirmed until the Tour de France nears its end. The International Cycling Union (UCI) approved race will be the athletes' only chance to ride the Olympic route on closed roads before the main event in July 2012.
For the organisers, it's a vital chance to iron out any problems with the route. They'll be testing the road closure system, signage and timing technology, identifying potholes that need to be repaired and road furniture that needs to be modified, making sure they've got enough marshalls (about 2,000 have signed up at the moment) and that the police escort works effectively, and ensuring that the layout of the start/finish area in the Mall works.
One of the biggest challenges will be the road closures. Gary MacGowan, head of road events for Transport for London, told BikeRadar: "TfL's responsibility is closing the roads for the race route, and to that end we have to work closely with Surrey County Council, six London boroughs, the Royal Parks and National Trust. There are about 1,000 road closures to implement, that's about 80km of barriers – twice the amount we put up for the Tour de France in 2007."
All the roads along the route will be closed for at least five-and-a-half hours, with those through Richmond and Bushy parks shut for the whole day. You can find details of the closures in London here and the closures in Surrey here.
Spectators are being urged to use public transport where possible, and to this end maps showing Tube and railway stations along the route and areas to avoid have been published. Congestion is inevitable, so if you want to watch, get there early – the race is due to start at 9am (you can view the schedule here). Organisers say there are "almost infinite" viewing opportunities along the route, especially in the royal parks, on the roads in and out of London, and in some of the more rural areas.
However, access to the Mall and parts of Box Hill will be limited – in the latter case, due to its status as a nature reserve and Site of Special Scientific Interest. You'll need a wristband to get in, and not many will be issued – 3,500 for the Mall and 3,400 for Box Hill. These will be available from local councils and British Cycling. Cycling Plus magazine will also be giving some away.