Start by shooting the scene in one long shot, as quickly as you can. You have to shoot fast because if the light outside shifts, you wont be able to mask the layers together convincingly. Start by having the cars shoot pass the camera... then have your actor play out the scene by jumping over one car, then getting hit by the next. Finally, have your actor run over to and get under the offending car.

Next bring all your footage into After Effects or whatever effect software you use. Separate your footage and have the clip of your actor as the top layer. Now line up all the clips so the timing matches, and mask all of the layers together.