JAX Controller described a potential aircraft/vehicle conflict when an aircraft was cleared for a touch and go with an airport vehicle runway check in progress. The vehicle cleared the runway prior any conflict.

Narrative

VFR Cessna in Tower pattern; sequenced with arrival to crossing runway; required beacon code change after touch and go. Operations vehicle was on the runway doing an opposite direction runway sweep to the runway the pattern aircraft would use. Due to issues related to beacon code change; aircraft turned final with touch and go clearance while vehicle was still on Runway. Operations vehicle saw the aircraft turn final and exited on his own while traffic was on final. Had he not done so; I'm not sure he would have made it to the end before the aircraft crossed the threshold. Discussion between myself and Local Control regarding the sequencing of the aircraft reference traffic to the other runway; followed immediately by the new flight plan for the Cessna being delivered by Clearance Delivery made us both lose track of the vehicle. I think putting the pattern aircraft on the runway not being inspected is one option but this was a one in a million event that I don't think specific mandatory procedure could have prevented as all of the existing facility memory joggers were in use.