It is very similar to an all forwards Autotest, the route is defined by a series of numbered ‘gates’, simply drive through the gates in specified order (increasing or decreasing numerical order).
As the name implies it is up to the driver to follow the route, passengers are not allowed so there is nobody to blame.
Tests usually start and finish at the same place with the whole route visible to the start / finish marshal although there will usually be a couple of spotter marshals to help check that the correct route is followed and replace any cones.
AutoSOLO vehicles must be road legal, taxed, tested and driven to the venue.
Autotest vehicles do not need to be road legal and can be trailered to the venue.
Production Car Autotest vehicles do not need to be road legeal and can be trailered to the event BUT a passenger MUST be carried.