Narrative:

Aircraft X was instructed to line up and wait on runway 28R. After issuing a takeoff clearance; the pilot advised he had 'red lights'. I then instructed the aircraft to hold in position and rescanned the runway at which point I noticed an unidentified vehicle crossing at taxiway 'F' moving in a southbound direction. After verifying that there were no further conflicts; I then once again cleared the aircraft for takeoff.rwsl [runway safety lights] worked as intended in this instance; recommend installing this safety feature in all runways at ord.

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Original NASA ASRS Text

Title: ORD Tower Controller reported clearing an aircraft for takeoff. Pilot reported they had 'red lights on the runway'. Controller advised pilot to hold position and observed an automobile on the runway. After vehicle was cleared aircraft was given takeoff clearance again. Controller liked the fact that the Runway Safety Lights Worked.

Narrative: Aircraft X was instructed to Line Up And Wait on Runway 28R. After issuing a takeoff clearance; the pilot advised he had 'red lights'. I then instructed the aircraft to hold in position and rescanned the runway at which point I noticed an unidentified vehicle crossing at taxiway 'F' moving in a southbound direction. After verifying that there were no further conflicts; I then once again cleared the aircraft for takeoff.RWSL [Runway Safety Lights] worked as intended in this instance; recommend installing this safety feature in all runways at ORD.

Data retrieved from NASA's ASRS site 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.