Detector system planned on Southwest Corridor

Posted 4/3/09

The Regional Transportation District plans installation of a system to detect intrusions by the end of the year along the Southwest Corridor Light …

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Detector system planned on Southwest Corridor


The Regional Transportation District plans installation of a system to detect intrusions by the end of the year along the Southwest Corridor Light Rail tracks as a safety measure because the light rail tracks are very close to the freight rail tracks.

Freight train derailments disrupted light rail service in 2007 and again in January. The concern about the possibility of light rail trains crashing into debris caused by a freight train derailment prompted the effort to identify and install an intrusion warning system to keep RTD passengers safe.

Pranaya Shrestha, RTD systems engineering manager, said RTD evaluated several technologies and prefer a system of seismic detectors. The detectors are programmed to pickup ground vibrations caused by a freight train derailment and send out warning signals to trains along the corridor.

He said RTD representatives and the consultant will do a “walk through” this month of the stretch of track from Evans to the end-of-the-line station at Mineral Avenue to evaluate the scope of the project. The data collected from the evaluation will help RTD engineering division prepare the specifications for the system. RTD will then ask the contractor for a bid and, if the project can be funded, the goal is to award the contract by the end of May and have the system installed by the end of the year.

Shrestha said the system plans proposes installing a seismic detector in each signal equipment vault along the stretch of track from Evans to Mineral. Each vault is reached through a manhole and the manholes are 500 feet apart. The seismic sensors will be adjusted to filter out the normal vibrations caused by passage of a freight train and light rail train. However, if the sensor picks up vibrations strong enough to be a freight trail derailment, it would send a signal to all the lights down the track, switching them to red. The engineer said the signal also would pass to the trains and shut off the power to those along that stretch of the track.

Early detection of a derailment is critical because, light rail trains south of Littleton hit speeds as high as 55 miles an hour and, at that speed, it takes about 600 feet to bring it to a stop with emergency braking.

Shrestha said he is not aware of any other light rail system using the seismic warning system but it is widely used along freight rail tracks.

The light rail tracks from Evans to Mineral are the only candidates for the intrusion sensing system. The freight train tracks run parallel to the light rail tracks from California to Union Station but the tracks are quite a bit further apart and the light rail trains move slower, about 25 miles an hour, the engineer said.

Shrestha said the engineers have no idea what it will cost to install and hook up about 50 seismic detectors, However, he said RTD is receiving $5 million from the federal stimulus package and that money is tentatively earmarked for the sensor project.

RTD evaluated several possible technologies including an electric warning fence along the edge of the track, a motion detector system using microwave transmissions and the seismic detector system.

The electric warning fence, along rail tracks in the mountains to detect rock slides, was ruled out because of the possibility of vandalism and the space it would take up. The microwave system was deemed to be susceptible to false detection such as snow or hail triggered the system so it was ruled out. The result is RTD now proposes using the seismic detector system,

The decision to install the intrusion detection system came as a result of the two freight train derailments in two years, in 2007 south of Arapahoe Community College and last year adjacent to the downtown Littleton station.

Shrestha said RTD looked as several possible systems, including

The tracks from Evans south to the Mineral Station are on a narrow right-of-way. The result is the freight train tracks are close to the light rail tracks. In some cases, the light rail and freight rail tracks are only 16 feet apart.

In 2007 when the coal train derailed and several cars dumped their contents on the light rail tracks, the northbound light rain train hit the coal on the track and, while several cars were derailed, no one was injured.


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