LGT LANDED ON OCCUPIED RWY; TWR FORGOT ABOUT VEHICLE MAKING RWY CHECK.

Narrative

HOW PROB AROSE: VEH ALLOWED ON RWY 28 FOR RWY CHK. LGT ON 8 MI FINAL CLRED TO LAND ON RWY 28. DISCOVERED: VEH ADVISED CLR OF RWY AND THANKS FOR TELLING ME THAT ACFT WAS LNDG. CONTRIBUTING FACTORS: FIELD OF VISION MIDFIELD RWY 28 OBSCURED DUE TO RAMP LIGHTS ON S CONCOURSE. VEH DRIVER MAY HAVE BEEN OUT OF VEH W/O ADVISING. LNDG RWY 28 WITH WINDS 100 DEGS AT 10 KTS; DUE RVR PREVIOUSLY BELOW MINIMUMS FOR RWY 10 FOR 20 MINS. REDUCED VIS THOUGH RWY WAS VISIBLE FROM TWR. ACFT READY FOR DEP OFF RWY 14; WAITING ACFT TO CROSS INTXN LNDG RWY 28. LCL AND GND CTL POSITIONS COMBINED APPROX 10 MIN. CORRECTIVE ACTIONS: NONE; LGT NEVER ADVISED SEEING THE VEH AT APPROX MIDFIELD. INACTIONS BY TWR CTLR IS THE PROBLEM. INACTIONS OF VEH DRIVER TO ADVISE POS AND QUESTION WHERE THE ACFT IS HE WAS TOLD ABOUT PRIOR TO ENTERING RWY. INACTIONS OF SUPVR IN TWR TO ACT AS AN EXTRA PAIR OF EYES. FACTORS: LCL CTLR WHO COMBINED POSITIONS HAD BEEN 2 HRS ON POS AT TIME OF INCIDENT. REMAINED ON POS 20 MORE MINS TILL RELIEVED. LCL CTL HAD BEEN TWR LONGER THAN PEOPLE ON OTHER 3 POSITIONS. TFC WAS SLOW; MAIN INTEREST SHIFTED FROM VEH ON RWY OT ACFT THAT WANTED TO DEPART RWY 14 ALONG WITH POOR WX; BRAKING AND 10 KT TAILWIND.