A DC9 AT THE BUF ARPT; HOLDING SHORT OF THE RWY; TAXIED INTO POS WHEN THE CTLR SAID; TAXI TO RWY 5. TFC ON SHORT FINAL WAS SENT AROUND.

Narrative

LCL AND GND CTL COMBINED. RWY 5 IN USE (APCH END DIFFICULT TO SEE BECAUSE OF POORLY MOUNTED RAMP LIGHTS; DARKNESS; RAIN AND OBSTRUCTIONS). SEVERAL MINS AFTER I ASSUMED LCL CTL AND GND CTL A DC9 CALLED; 'READY.' I ASSUMED THE ACFT MEANT READY TO TAXI BECAUSE ON THE POS RELIEF FROM THE OTHER CTLR NOTHING WAS MENTIONED ABOUT A DC9 TAXIING; THE ACFT IDENT WAS NOT WRITTEN DOWN ON THE SCRATCH PAD; AND THE FLT PROGRESS STRIP WAS IN THE INACTIVE BAY. I RESPONDED 'ACR X TAXI RWY 5.' ACFT RESPONDED 'ACR X ROGER.' I DID NOT HAVE ANY GND TFC BTWN DC9'S RAMP AND RWY. I LOOKED TOWARD THE RAMP AND SAW AN ACFT WHICH I ASSUMED WAS THE DC9; BUT WAS AN ACFT PARKED NEARBY. I CLRED THE B737 TO LAND (WX 400 FT OVCST). THE DC9 ASKED 'WHAT RWY WERE WE USING?' I RESPONDED RWY 5. DC9 THEN ASKED WHERE THE B737 WAS. I RESPONDED A 1 1/2 MI FINAL. THE DC9 THEN INFORMED ME THAT HE WAS ON THE RWY. THE B737 WAS ON A SHORT FINAL AT WHICH TIME HE WAS SENT AROUND. CAUSES: POOR POS RELIEF BY PRECEDING CTLR. ASSUMPTION BY DC9 PLT THAT 'TAXI RWY 5' MEANT THAT HE COULD TAXI INTO POS. NO READBACK BY PLT. LIGHTING CONDITIONS. ASSUMPTION BY MYSELF THAT PARKED ACFT WAS THE TAXIING ACFT.