The driver of a Rescue and Fire Fighting Service (RFFS) vehicle intended to carry out a routine road test, using the runway at Devonport. He received approval to enter the runway from the duty Flight Service Unit (FSU) officer. While the road test was in progress, the pilot of the aircraft reported that he was taxying for departure. The FSU officer apparently overlooked the fact that the RFFS vehicle was on the runway, and advised the pilot that there was no traffic in the area. The driver of the vehicle did not hear this exchange. Prior to entering the runway, the pilot checked for other aircraft, but did not sight the RFFS vehicle. As the pilot commenced his take-off run, the vehicle was heading towards the taxyway intersection from the opposite end of the runway. The pilot saw the vehicle in time to become airborne and pass over the top of it. The driver of the vehicle sighted the aircraft as it became airborne, and also took evasive action. It was likely that the pilot did not sight the vehicle earlier because of sun glare, and visibility from the cab of the vehicle was temporarily impaired because foam from the monitor had sprayed onto the windscreen during the test procedure. In order to prevent similar occurrences in the future, RFFS vehicles conducting test runs are now required to have a minimum of two crew members on board, and new procedures have been implemented at the FSU to alert the duty officers when vehicles are using the runways.