I've been to the Velo, tbh it's a nightmare to shoot.
You're not allowed into the infield unless you're with a team or have some other specific function, so it confines all you're shots to the outside of the track.
If you have a long enough lens you can get the entry to the bend and the exit from the bend, these are pretty steeply banked and can be a challenge for the most experienced rider to complete cleanly. The infield has a nasty blue track around it and a railing that clutters you're shot too.
Lighting.......hmm, thats another wee issue, the spot lights are angled towards the outside of the track from above the infield, during practice they tend to have them quite low but then crank them up for the races.
tripods just get in the way, I think a monopod would be better tbh.
Interestingly you're allowed to use flash, but I'm not sure you'd be liked too much if you blinded a rider
Oh......and one more we note, if Team GB are riding.....you can't photograph them....same for minors!