Wayside Intrusion Detection System (WIDS)
105 Freeway, Los Angeles

Client

Los Angeles Metropolitan Transportation Authority (LAMTA)

General Contractor

L.K. Comstock

Project

Wayside Intrusion Detection System (WIDS)

Scope of Work

34 miles (17’ miles each direction) of 5′ high chain link fencing with top and bottom aircraft cables and four sensors running through the fence panels, built on top of a 3 ½’ concrete barrier on both sides of the Metro Green Line running in the middle of our fence line. Project includes the fence in the Park and Rides and the handrails in a total of seven train Stations alongside the 105 Freeway. (Known as Century Freeway.)

Project Description

This chain link fence is the typical galvanized material, but it was termed a Smart Fence because there were four sensors intertwined in the chain link fabric. These sensors were capable of alerting the Control Tower if at any given time, an object hitting the fence could inflict a deflection of more than 12” in the fabric of the chain link. In the event this would occur, the Control Tower can alert the incoming trains immediately.

The specification for the WIDS fence was unlike any other we have dealt with before. The fence has to withstand the force of a 60 lbs. object traveling at up to 70 miles per hour and the fabric of the mesh has to endure the impact of a 3” ball size object traveling at 35 miles per hour and not penetrate through the fence mesh.

Ace Fence had to undergo a series of tests that lasted over 2 weeks. We built a mock-up fence of 1000 L.F. alongside the Freeway. We brought in a 30’ high crane and hang a 60 lb. steel ball on top of the crane and swing it in the direction of the fence line at the calculated speed of 70 miles per hour. For each area hit, the Engineers from the LAMTA would carefully measure the deflection of the fabric to insure that it does not deflect over the allowed 12” to either side of the fence line.

The hardest part about this job was the time constraint. The Freeway was scheduled to be inaugurated October 15, 1993. It was already July 28 when our crews have not even moved in to the jobsite yet. There were delays on the building of the underlying wall that supported our fence line on top of it.

Ace Fence moved in August 1 and we worked with a crew of 125 Union workers and 25 flatbed trucks. In the middle of the Construction we had an unwanted, yet interesting delay to our already neck-breaking schedule. The LAMTA decided to sign a contract with 20th Century Fox to film some scenes of their upcoming movie Speed (with Keanu Reeves and Sandra Bullock). Our crews had to stop their work and step aside every time the yellow bus and all the 100 prop cars had to drive by the Freeway with the big truck filming in front of the whole action. Despite all of these interruptions, Ace Fence was able to deliver a final product exactly on the morning of October 15. Our trucks were the last ones to march out of the completely empty Freeway at 6 a.m. on that morning. This was probably the last time any of us saw the Century Freeway completely empty.