1. A computer program product for controlling an autonomous vehicle, the computer program product comprising a computer readable storage medium having program instructions embodied therewith, the program instructions executable by a processor to cause the processor to perform a method comprising: determining whether a primary user is present in an autonomous vehicle; allowing use of a plurality of functions of the autonomous vehicle in response to determining that the primary user is present in the autonomous vehicle; receiving and storing preferences input by the primary user, wherein the preferences identify a limitation on one or more of the plurality of functions of the autonomous vehicle that should be enforced during use of the autonomous vehicle if the primary user is not present in the autonomous vehicle; and limiting the use of the one or more of the plurality of functions of the autonomous vehicle as specified by the preferences in response to determining that the primary user is not present in the autonomous vehicle.