I've done some driving work for a car magazine doing what they call "tracking" shots, which is basically car to car moving vehicle shots.
These are taken at low speed, usually 30mph, and the photographer simply hangs out of the chase car to take shots of the target vehicle, which is the one I'm driving.
The 'tog uses a pretty slow shutter speed, about 1/30th, and takes a burst sequence, the object being to get the target vehicle sharp but with blurred wheels and background.
(They take a LOT of shots.)
Sometimes the camera car can be a hatchback or estate and the 'tog sits in the back, which is fine when the target is following, but when the target vehicle is leading the 'tog either hangs out the rear side window, or sometimes shoots around the open door of the camera vehicle. For a regular car the photographer just shoots from an open side window or out of the open rear door.
The important thing is that these shots a normally taken on a closed test track for safety, although we recently had to do a two-car shoot on a quiet country road.
The thing is, there is no "rig" involved in these shots, just a person with a camera (and quite a bit of experience.)