Will Speed Trap leaderboards be classified by car class and type?
In this E3 video interview Ralph Fulton says no, but describes the 3-star system for speed traps, speed zones, danger signs, and drift zones. For each star you earn new fans. Beyond 3 stars you start to earn Open World Points.
/!\ Why is my lap marked dirty if I did nothing wrong?
Reasons for a lap being marked with the /!\ dirty lap symbol include: contact with a car or wall, heavy bottoming out (ride height too low/suspension too soft), driving outside the track boundary, drafting (either ahead or behind a close car), driving the wrong way on a track, using Rewind, or using Mods that affect car performance. Triggering a dirty indicator in the final sector of a lap will also cause the next lap to be dirty (due to the possibility of gaining an advantage entering that lap); rewind back beyond where the last split time pops up in order to keep the next lap clean. You may find it difficult to get a clean lap with other cars on the track; to improve your leaderboard rank, use Rivals to race alone on the track.
(Written by Manteomax)