Cessna Citation Mustang (C510)
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Flight Crew Last 90 Days 43; Flight Crew Total 4530; Flight Crew Type 905
Confusion; Distraction; Situational Awareness
ATC Issue All Types; Conflict Ground Conflict; Less Severe; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural FAR; Ground Incursion Runway
Air Traffic Control Issued New Clearance; Air Traffic Control Issued Advisory / Alert; Flight Crew Became Reoriented; Flight Crew Requested ATC Assistance / Clarification
Human Factors; Airport
Ground control instructed me to back taxi on closed runway 04 to intersecting active runway 31L. Arriving at runway 31L I became confused because of multiple hold short lines on 2 perpendicular taxiways G and N intersecting the 2 perpendicular runways 04/31L. There are 6 hold short lines in near proximity on the taxiways and runways at these intersections. The painted lines on both runways are weathered and partially obscured with rubber tire marks. I mis-interpreted the hold short line on runway 04 to runway 31L. I turned on to active runway 31L to stop at the hold short line for runway 04. I checked in with the tower. Then I told tower I thought I was on runway 31L. The response was to hold short. Soon I was cleared for takeoff.Upon departure I was instructed to call either of 2 phone numbers for possible pilot deviation. I've called both numbers 5 days in a row with no answer and no return phone call. I have since studied aerial photos and airport diagrams. I now see my error of mistaking which hold short line was intended for which runway. Study airport diagram better and request a progressive taxi from ground control at unfamiliar airports.
Corporate pilot reported crossing runway hold short line due to confusing instructions and unclear signage at SAT.