"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."
2 track stands of 30 seconds each according to: http://www.usacycling.org/forms/RdTrkCx_rulebook.pdf
"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."