copy and paste beetwen two projects

Ok, I have 2 projects, one contains a car with its phisics, meshes etc.
The other one contains the MAP.
I need to copy the car into the one with the map or vice-versa. How it can be done?

shift-F1, append or link …

thanks, this helped a lot. The problem now is that I can see the imported objects only in oops schematics, and they look inactive?

After selecting the file you want to Append/Link from, choose Object (not Mesh) and then select the actual object by name.

perfect, thanks.