• In a team time trial every member of a team leaves at the same time with seven minute intervals between teams.
• When the team's 5th rider crosses the finish line the clock is stopped.
• Riders 1 to 5 get the 5th rider's time.
• Riders 6-9 get their own individual time.
• For the team classification the 5th rider's time is recorded as the team's time.
• Any rider who doesn't finish within the cut off time is eliminated from the rest of the Tour de France.
• The cut off time for tomorrow's TTT is 25% of the fastest team's time (roughly +10m).

The 39km TTT course

In the Giro d'Italia the TTT was a dead flat course, a there and back 10km stretch where sheer speed was the deciding factor.

Columbia won 6s ahead of Garmin, with Astana 13s behind.

The Tour de France course is quite different. It is a technical course with climbs, turns and the added variable of the possibility of side winds. The teams are expected to be on the course for around 43 minutes, that's a 54km/h average speed!

Who are the favourites?

SaxoBank, Garmin Slipstream, Team Columbia HTC, Cervelo TestTeam and Astana are the five teams to watch tomorrow.  Each team has slightly different motivation for doing well making this short race one of the most interesting stages to follow.

• Garmin Slipstream want to win.  This stage is the primary focus of their whole 2009 season.
• Saxobank want to get Andy Schleck in the yellow jersey before heading to the mountains this weekend.
• Team Columbia HTC, their super-powered team is used to winning and tomorrow is no exception.
• Astana's objective is to create a time gap buffer back on their potential rivals, in particular Cadel Evans of Silence Lotto.
• Cervelo TestTeam know they have to work hard to minimise losses for their GC rider, defending Tour de France champion Carlos Sastre.  With the focus they have placed on this event, can they pull off an upset?

How can a short 40km TTT make a difference to the overall standings?

Not all teams are created equal.  The inclusion of the TTT forced teams to look carefully at their Tour selection.  Teams with top GC hopes usually fill their team with climbers, but most climbers can't time trial, their small frames don't have the power needed for  a TT.  Teams can't afford to lose minutes in this stage on a Tour that can be won or lost on a few seconds.

Some teams have many overall strong riders, some teams opted to stack their nine riders in favour of winning sprint stages and one team in particular has a leader who's level is higher than that of his team - Cadel Evans. Evans is likely to be the rider with the most to lose in tomorrow's stage.

Looking at the Stage 1 individual time trial as a crude view of form, the team whose 5th rider had the fastest time was Astana, only 1m15s slower than the top overall time. Silence Lotto's 5th rider was 2m02s slower. That's 47 seconds faster over 15kms and the TTT is 40kms. This is a crude method but it does highlight the potential losses a team can sustain if they haven't put the right focus on this stage.