When does a trackstand "officially" ends (or how to measure its duration?)

Question

Trackstands (a trick in which a rider, usually on a fixed-gear bike, keeps balanced with zero speed, by pedalling back and forth with minimum displacement) can be employed either on the track or on the streets, mainly at traffic lights.

In the track, the rider can slow down and create a hard time for an opponent. On the traffic light, one can keep himself on the bike and be ready to go. That makes the trick "desireable", so it is either regulated on official events, and used itself for "trackstand competitions", mostly in the fixie subculture.

What I have to ask is:

• What are the UCI criteria for the judge to stop the countdown for trackstand duration?
• What are the criteria traditionally used on informal competitions for taking a "competitor" out?
• What SHOULD BE a reasonable way to tell when a rider degenerated from a correct trackstand to something else (forward or backward movement, too large a change in position, etc.)?

Thanks for reading!

Answer 1

(too big for a comment)...not a real answer, just a partial:

From UCI part 3:

3.2.039 The rider on the inside of the track, unless overtaken, shall lead at least at walking pace and make no manoeuvre to force his opponent through until reaching the pursuit line on the opposite side of the track. A maximum of two standstills shall be permitted for each race. The maximum period for a standstill shall be 30 seconds following which, the leading rider shall be directed by the starter to continue. If he fails to do so, the starter shall stop the race and declare the other rider the winner of the heat. In a three or four-up race, the race shall be immediately rerun as a two or three-up race, without the relegated rider.