Tower controller described a loss of separation event when authorizing an airport vehicle to operate...

Attributes
ACN	935438
Time
Date	201103
Local Time Of Day	0001-0600
Place
Locale Reference	ZZZ.Airport
State Reference	US
Aircraft 1
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	Landing
Route In Use	None
Flight Plan	VFR
Person 1
Function	Local
Qualification	Air Traffic Control Fully Certified
Events
Anomaly	ATC Issue All Types Conflict Ground Conflict Less Severe Deviation - Procedural Published Material / Policy

Narrative:

A maintenance vehicle requested to enter the runway and proceed to the under-run to take down a barrier. I approved the request and approximately 15 minutes later aircraft X requested to land. I cleared the aircraft to land and he exited without incident. About 5 minutes later the maintenance vehicle reported job complete and requested to exit the under run. This call made me aware of the event and no one knew besides me; not even the vehicle or aircraft. I essentially forgot I had a vehicle at departure end under run. Recommendation; my memory aid was nearby and I didn't use it. As soon as any vehicle is on any runway we always pull out our vehicle placard.

Original NASA ASRS Text

Title: Tower Controller described a loss of separation event when authorizing an airport vehicle to operate on the approach end of the runway and later cleared an aircraft to land; the reporter acknowledging the failure to use existing memory aids.

Narrative: A maintenance vehicle requested to enter the runway and proceed to the under-run to take down a barrier. I approved the request and approximately 15 minutes later Aircraft X requested to land. I cleared the aircraft to land and he exited without incident. About 5 minutes later the maintenance vehicle reported job complete and requested to exit the under run. This call made me aware of the event and no one knew besides me; not even the vehicle or aircraft. I essentially forgot I had a vehicle at departure end under run. Recommendation; my memory aid was nearby and I didn't use it. As soon as any vehicle is on any runway we always pull out our vehicle placard.

Data retrieved from NASA's ASRS site as of April 2012 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.

Tower controller described a loss of separation event when authorizing an airport vehicle to operate on the approach end of the runway and later cleared an aircraft to land; the reporter acknowledging the failure to use existing memory aids.