I had a brief vacation in San Diego a few weeks ago and though I was working we went on a walk in the morning to check out the velodrome in Balboa Park. Amanda and Kayla were interested in the strangely sloped track and I tried to explain the weirdness of the races I'd seen online.
Watch the linked video. The racers go exceptionally slow at the start because they're trying to get into the second place position. The idea is to stay just behind the leader until the last lap when you use the slipstream of the person in front to catapult yourself past him at the finish. This dynamic makes the races interesting, the leader tries to fake out his opponent and they often come to a stop on the track. Then in the last lap they accelerate to 70kph for the finish.
As we stood watching the track a few older men and women drove in. I assumed they were referees until they reached into their cars and removed expensive looking, fixed gear carbon fiber bikes. I doubt they were were there to do any sprints but it would have been fun to see.