PLTDEV WHEN AN ACR CROSSED THE COMMON HOLD SHORT LINE FOR RWY 23L AND RWY 28L AND TAXIED ONTO RWY 23L.

Narrative

ACFT #1 WAS CLRED TO TAXI TO RWY 28L BY GND CTL. ACR TFC WAS ON A 5 MI FINAL TO RWY 28L. ACFT #1 PASSED THE RWY 28L HOLD SHORT SIGN AND TAXIED ONTO RWY 23. AS SOON AS I NOTICED; I CALLED AND INSTRUCTED THE PLT TO HOLD POS. THE PLT ACKNOWLEDGED AND STOPPED. JUST OVER 1/2 OF HIS ACFT EXTENDED BEYOND THE HOLD SHORT LINE. SINCE THERE WAS AMPLE CLRNC (MORE DISTANCE EXISTED FROM THE NOSE OF THE ACFT TO RWY 28L THAN AT ANY OTHER RWY 28L HOLD SHORT LINE) I ALLOWED THE OTHER ACFT TO LAND ON RWY 28L. THERE WAS NO TFC LNDG OR DEPARTING ON RWY 23. THE PLT ADVISED THAT HE EXPECTED TO FIND RWY 28L HOLD SHORT SIGNS ON RWY 23. THE PLT WOULD NOT HAVE SEEN ANY HOLD SHORT SIGNS (OR LINE) WHERE HE EXPECTED AS THE HOLD SHORT SIGNS FOR RWY 28L AND RWY 23 ARE COINCIDENT. IT IS MY BELIEF THAT THE SIGNAGE IN THIS AREA IS CONFUSING. IF THIS SIGNAGE MEETS MINIMUM FAA STANDARDS; I BELIEVE THESE STANDARDS ARE FLAWED; AS I HAVE OBSERVED NUMEROUS OCCASIONS OF SIMILAR PLT BLUNDERS AT THIS INTXN. I HAVE EVEN SEEN A KING AIR PLT ATTEMPT TKOF ON RWY 23; THINKING IT WAS RWY 28L.