Date: 201501
Local time of day: 1201-1800
Location: STS.Airport, CA
Flight conditions: VMC
Light: Daylight
Aircraft: Light Transport
Operator: Fractional
Operating under: Part 135
Mission: Passenger
Flight phase: Taxi
ATC / advisory: Ground STS
Reporter organization: Fractional
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown; Confusion; Situational Awareness
Anomaly: ATC Issue All Types; Deviation / Discrepancy - Procedural Clearance; Ground Incursion Taxiway
Detector: Person Air Traffic Control; Person Flight Crew
When detected: Taxi
Result: Air Traffic Control Issued Advisory / Alert
Contributing factors: Chart Or Publication; Airport; Human Factors
Primary problem: Airport

Narrative: Santa Rosa Ground gave us our taxi clearance; 'RWY 14; taxi via A4; and A'. We started taxiing; just after passing Hotel Taxiway; I noticed the red 'APPR 20' sign off to my left; in the vicinity of TWY H; as well as the end of RWY 20; but I never saw the hold line on TWY A for the Approach end of 20. This may have been because my eyes were diverted left to the sign; instead of the pavement; trying to figure out whether it applied to us. The pavement is separated between TWY A; and RWY 20; and the APPR 20 sign is just past TWY H; at an angle; so it was also confusing whether the sign was intended for TWY A or TWY H. In the taxi clearance; controller did not specifically state 'Hold Short Approach end of RWY 20'. While clearly; absence of those instructions does not give us permission to cross a hold line; neither of us SAW the hold line associated with the APPR 20 sign; and we continued. We may have already passed the line at that point. Approaching RWY 14; the controller called us and said; 'In the future; keep in mind you are not allowed to cross the approach end of 20 without permission'; or something to that effect. I immediately checked the chart to see if I had missed something; if there was a note; or a hotspot. There was not. There was no traffic on short final for RWY 20; or in the traffic pattern for RWY 20; so there was no traffic conflict. Looking back on what happened; I think there were two mistakes that happened that day. The controller never issued us the 'Hold Short Approach end of [Runway] 20' instructions; and we missed the hold line. The controller that day admitted that it was busy in the tower at the time; and he may not have given us the instruction. The signage; and angles of the runways and taxiways lead to confusion in that area; as well. Even with the APPR 20 flashing sign; because of the taxiway and runway angles at that spot; and the fact that the pavement on TWY A is totally separate from RWY 20; there was just enough confusion about whether we were supposed to stop or not. In hindsight; I should have stopped to clarify; but we saw no hold short line (in hindsight; we were probably already past it; but did not realize it); so we continued.I called Santa Rosa Tower the following morning to discuss the issue. Apparently; I'm not the only one that has been confused by the signage. When I asked if there was indeed a hold line on TWY A; he said 'Yes; but you probably didn't see if it if you were looking at the sign'. I was told that this happens quite frequently; and that it is a known problem on that area of the field. The controllers have filed multiple safety reports as well about this area. Apparently; the process has been started to get a hot spot note annotated on the chart; and they are looking for ways to make the signage less confusing. One possible idea was to paint the APPR 20 sign on the pavement itself; directly on TWY A; just past TWY H. Maybe the new flashing lights on the taxiway itself would help. Maybe moving the hold line would help; although I can't say that for certain; because I never SAW the hold line. Whatever solution they can come up with to make the signage less confusing in that area would be most welcomed; in the interest of safety. The controller I talked to on the phone also made a note that we weren't given the 'Hold Short' instruction; and said he would pass that along on his end for the controllers to be more vigilant in giving this instruction.




Synopsis: When the flight crew of Light Transport aircraft was cleared to taxi to Runway 14 via A4 and A at STS they taxied across the extended centerline of the approach to Runway 20. Ground Control advised that next time they should hold short for clearance. The flight crew cited confusing signage at the location as a contributing factor. Ground did not include a hold short instruction in their taxi clearance.