A warning system that is supposed to alert truck drivers if they're too tall for a Pittsburgh tunnel is back in service after years of not working following last week's incident of a truck getting stuck inside.

Last Thursday, Ontario trucker David Murley got stuck about 100 feet inside the Squirrel Hill Tunnel on Parkway East. His load was 14 feet, 4 inches high; the tunnel is posted at 13 feet, 6 inches. It took the Pennsylvania Department of Transportation and a local towing service more than three hours to free the truck, backing up traffic.
The Pittsburgh Post-Gazette reports that an over-height warning system has been broken for years. The Pennsylvania DOT has been working to upgrade the warning equipment, and it was turned on the day after the accident.
Two poles are set on opposite sides of the highway, and electric eyes are mounted on top at 13 feet, 6 inches. When a truck that's too tall breaks the beam, sensors set of an alarm. The first set of sensors activates a sign alerting the trucker to exit. The second set is just before the tunnel entrance, where an overheight truck will set off amber warning signs, turn on a red "X" sign indicating the tunnel is closed, and sets of an alarm in the tunnel workers' office.
In the old system, the paper reports, a PennDOT worker would come out with a stop sign and wave the trucker to a stop, then stop traffic so the truck can turn around. In the new system, a stop sign is painted on a plastic gate that is rolled down manually at the tunnel entrance.
PennDOT officials say the system was unreliable, with bad weather, changes in voltage or even birds creating false alarms or shutting the system down. Lockheed Martin was working on the upgraded wiring and new warning signs, but official couldn't say why the system was not working Thursday when Murley approached the tunnel.