In the past, World Championships finals have been preceded by a seeding run allowing the riders (and team managers) to employ some tactics to combat weather changes and generally mess with peoples heads by seeding low down the order. The new system uses the UCI ranking to seed the riders, with a mandatory timed training run to allow the riders to gauge their speed against their competitors.
http://mpora.com/videos/HEC916xgl
Dirt TV: World Championships Timed Training >>