A Denver Rail Agency has called for the introduction of intrusion detection technology after two freight trains derailed in the past two years.

The Regional Transport District (RTD) plans to install the intrusion detection system along portions of the Southwest Corridor light-rail line as a safety measure to prevent collisions if a freight train derails in the corridor.

RTD is looking at three possible technologies for intrusion detection.

The most promising technology is underground sensors, which use seismic equipment to pick up any unusual sounds and then send a signal for nearby trains to stop.

A second option is an electronic fence that runs above ground along the right of way between the freight and light rail tracks. If a freight train derails, its cars or cargo would break the wire circuit and halt trains. The technology is similar to what freight railroads use in the mountains to electronically detect rockslides.

Third is the creation of an intrusion barrier using microwaves from transmitters set up along the rail corridor. This technology, however, is susceptible to false reports of intrusions from snow or fog.

RTD’s rail operations chief, Cal Shankster said that for the first seven years of the Southwest light rail’s operation, no freight derailments affected RTD’s operation.

“The two recent ones have pushed the transit agency to install intrusion detection equipment that will warn of a freight derailment through the signal system and stop all RTD trains in the area,” he said.

RTD plans to use $5m in federal transportation stimulus money for the detection project.

In 2007 a southbound Union Pacific coal train derailed just south of Arapahoe Community College and in January a southbound BNSF freight train derailed as it was passing Littleton light rail station. UP and BNSF officials attributed the cause of both derailments to broken rail on the freight line.

By Daniel Garrun.