Never film from a moving vehicle without supporting the camcorder. You can get specially designed mountings for doing this, or you can use a
unipod. If you're shooting on celluloid, its better to use a higher
film speed to iron out any bumps that may occur.
Alternatively, you can use a conventional
tripod set on the floor of a car, so long as you make sure it doesn't move during filming. Working with your
zoom lens in the wide angle position, you can film the driver from the rear seat. It is always best to use a cable release. Also, to prevent over exposure, you will have to override the automatic controls and set the aperture manually.