I read about that before.... he said the jet could push the car along by itself at highway speeds....
The only way this would be a clean way to travel would be a clean fuel
I don't see how you could make it safe.... burning the front end of a car too close behind you and fuel containment .... I don't think you could ever get it to pass an inspection.
Oh by the way... you can buy jet engines like this for the bigger remote control jets that people fly...
for instance... here are some that go up to 35Lbs of thrust from a 3.34 LB Engine.... also runs on jet fuel or kerosene.
http://www.quicktechhobby.com/Engines/Q ... NGINES.htm
The one in the first post I think was 85Lbs of thurst for the EV-1.