  This paper describes (R)ules (o)f (T)he (R)oad (A)dvisor, an agent that
provides recommended and possible actions to be generated from a set of
human-level rules. We describe the architecture and design of RoTRA, both
formally and with an example. Specifically, we use RoTRA to formalise and
implement the UK "Rules of the Road", and describe how this can be incorporated
into autonomous cars such that they can reason internally about obeying the
rules of the road. In addition, the possible actions generated are annotated to
indicate whether the rules state that the action must be taken or that they
only recommend that the action should be taken, as per the UK Highway Code
(Rules of The Road). The benefits of utilising this system include being able
to adapt to different regulations in different jurisdictions; allowing clear
traceability from rules to behaviour, and providing an external automated
accountability mechanism that can check whether the rules were obeyed in some
given situation. A simulation of an autonomous car shows, via a concrete
example, how trust can be built by putting the autonomous vehicle through a
number of scenarios which test the car's ability to obey the rules of the road.
Autonomous cars that incorporate this system are able to ensure that they are
obeying the rules of the road and external (legal or regulatory) bodies can
verify that this is the case, without the vehicle or its manufacturer having to
expose their source code or make their working transparent, thus allowing
greater trust between car companies, jurisdictions, and the general public.
