In general, matters relating to road traffic and road transport are reserved where there is a need to ensure consistency of treatment and approach between Scotland and the rest of the United Kingdom.
The Scottish Parliament has competence to legislate about the promotion of road safety and about payments for hospital treatment of road traffic accident casualties.  Bus fuel duty rebate is also not a reserved matter, in line with other aspects of bus policy.
TABLE OF RESERVED MATTERS Head C: Trade and Industry Details of Provisions