Change-over rules for women's team sprint I have just been watching the women's team sprint finals, and sawsaw China lose the final race due to a rule infringement. Earlier the Great British team were disqualified for the same reason. There is a set region that one rider has to peel off and let the other pass through.

Despite the commentators' best efforts I still don't understand where this region is marked on the course.

Also I don't understand why there is such a rule at all. The lead rider allows the second rider to draft for the start of the race, so they want to stay in the race as long as they can, but they wouldn't want to stay in until the end. Is there a reason for a fixed change-over zone (e.g.safety), or is it just a rule that's always been part of the sport?
The rules for Track Races are here. In the Team Sprint:


  The leading rider shall lead the first lap and move towards the outside of the track and then drop back to leave the track without hindering the other team.


In Great Britain's semi-final this is what happened at the end of the first lap:



Jess Varnish (nearest to us in the picture) was the leading rider with Victoria Pendleton as the second rider. Jess Varnish should have lead for the whole of the first lap, unfortunately Victoria Pendleton overtook her before the first lap was completed and they were disqualified.

The same thing happened to the Chinese team in the final.