A real issue with any car is the likelihood extensive damage even after low-speed collisions. I totaled a Ford Taurus once in a parking lot doing only 5 mph. The bumper and front molding cracked, various metal parts behind that were bent, and the radiator burst. I couldn't believe how bad the damage was. So, with the solar car of wood I've designed a bumper that floats on four inches of expanded polypropylene foam, which has shape memory. That's in addition to the existing 2" foam block in front of the bumper. There's also another 2" hump in front of that as well as 1" foam above and below the lights. The fender corners are also floated on four inches of foam and the fenders themselves are polypropylene over wood. The front bumper will be held by heavy-duty spring fasteners, since polypropylene adheres poorly to other materials. My hope is this car can withstand a 5 mph collision with no damage and possibly a 10 mph collision with minimal damage. This, I believe, is really important in a city car!