racing by laps instead of time? (rule question)
so i checked out my first "official" race, which happened to be at kirtland park. part of the bike authority ohio series.
from what i could gather, the race length was determined by a preset number of laps, not time. whenever the front person would cross the start line, they would flip a card to one number lower (i.e. they are on lap seven, person crosses start again, the number gets turned to six). from reading stuff on here and other places on the web, i figured that cat 1 races were 1 hour in length, plus one lap, cat 3 were 45 minutes +1, and cat 4/novice were half an hour +1. when i have been practicing on my own; i was sort of following this assumption.
is either way, by a set amount of laps OR by elapsed time, acceptable to time the race? or am i just dumb and missing something?