Narrative:

Taxiing from cargo ramp to runway. Cargo ramp exits right to runway. I thought I was taxiing to a parallel taxiway. I taxied onto runway. No problem was caused.

Google
 

Original NASA ASRS Text

Title: AN ACR FLC FLYING DC9 FREIGHTER INADVERTENTLY TAXIES ONTO RWY AT SGF WITHOUT PROPER ATC CLRNC.

Narrative: TAXIING FROM CARGO RAMP TO RWY. CARGO RAMP EXITS RIGHT TO RWY. I THOUGHT I WAS TAXIING TO A PARALLEL TXWY. I TAXIED ONTO RWY. NO PROB WAS CAUSED.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.