Here is another example of the usefulness of a arm-style camera mount over a tripod. For this video I clamped the camera mount to the metal rod protruding from the bottom of the passenger seat head rest I also could have clamped it to the handle for the parking brake. Both of these mounting locations are firmly fixed to the car and help minimize the vibration of the camera while shooting.

The choice of frame rate is very open here because while the scenery will be moving outside your car the cars in front of you will be relatively stationary in the frame as you drive down the highway. Because of this, the choice of frame rate really depends on how fast you want to car to appear to be moving and what speed you will play the resulting movie at.

When I started driving I was facing west and the sun was setting so I chose a shutter speed on the camera that would avoid a totally blown out sky. However, as my drive continued I began heading north and the pictures begin to get darker. It wouldn't have been safe to adjust the exposure while driving (obviously). I think that it is a good idea to take a test photo in all directions (N, E, S, W) and choose some average value to avoid severely under or overexposed pictures if you will be changing direction while shooting.