RTD plans to install an “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.
At key points on their run between Denver and Littleton, light-rail cars on the Southwest line run very close to Union Pacific and Burlington Northern Santa Fe freight trains operating on adjacent track.
At the closest point, freight and light-rail track are only about 16 feet from each other.
In December 2007 and again this past January derailments of freight trains in Littleton buckled freight cars and tumbled them onto nearby Regional Transportation District rail right of way.
In the 2007 incident, a southbound Union Pacific coal train derailed just south of Arapahoe Community College, spilling coal and train wreckage onto RTD’s tracks just as a light-rail train was approaching from the opposite direction.
The lead light-rail car hit the debris and came off its track, but the passenger cars stayed upright and no one was hurt.
In the January incident, a southbound BNSF freight train derailed as it was passing next to the downtown Littleton light-rail station. The derailed freight cars ripped out a segment of the retaining wall that separates the freight and light-rail tracks and forced a long closure of light-rail service in the area. Again, no one was injured.
UP and BNSF officials attributed the cause of both derailments to “broken rail” on the freight line.
For first 7 years, no problems
For the first seven years of the Southwest light rail’s operation, there were no freight derailments that affected RTD’s operation, yet 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.
RTD plans to use $5 million in federal transportation stimulus money for the detection project.
The aim is to prevent light-rail cars from running into the wreckage of a freight derailment, said Cal Shankster, RTD’s rail operations chief.
For a light-rail train going 50 mph, it takes 600 feet for the cars to come to a stop after emergency braking, he said.
South of the Littleton station, the speed limit for RTD trains is 55 mph. The limit for freight trains in the area is 45 mph, Shankster said.
3 ideas: No. 1, underground sensors
RTD is looking at three possible technologies for intrusion detection, said Pranaya Shrestha, the agency’s systems engineering manager.
The most promising uses seismic devices that are placed in underground rail signal vaults along the right of way, Shrestha said. The seismic equipment is linked via conduit that carries signal wiring the length of the corridor.
If a freight train derails near RTD’s track, the seismic monitors will pick up the unusual sound and send a signal for nearby light-rail trains to stop, Shrestha said. The sound of normally operating freight and light-rail trains will be filtered out, he said.
No. 2, electronic fence, is vulnerable
Another technology being evaluated is a kind of electronic fence that would run 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 similarly halt light-rail trains.
This technology, similar to what freight railroads use in the mountains to electronically detect rockslides that may have covered track, is vulnerable to theft and vandalism in an urban rail corridor, Shrestha said.
No. 3, microwaves, risk false alerts
A third option — creating an intrusion barrier using microwaves from transmitters set up along the rail corridor — presents another problem. It is susceptible to false reports of “intrusions” from snow or fog.
So RTD is leaning toward the seismic solution, Shrestha said, especially for areas where freight and light-rail track are especially close to each other. The agency hopes to have the detection technology in place by this fall.
Intrusion detection cannot prevent all possible collisions between freight and light-rail trains in the Southwest corridor, RTD officials acknowledge. Where the tracks are close to each other, if a freight derailment occurred just as light-rail cars were going by, a collision might be unavoidable.
“What this buys us is a great reduction in the probability of contact in a freight derailment,” said David Genova, RTD’s chief of safety, security and facilities.
Jeffrey Leib:303-954-1645 or jleib@denverpost.com
Rules tougher for new rail lines
RTD would not be able to build a light-rail line like the Southwest Corridor next to freight rail tracks if the agency were constructing it today.
After a fatal train accident involving freight and passenger cars in the Los Angeles area in January 2005, freight railroads told the Regional Transportation District that only heavier and more crash-resistant commuter rail cars could operate near their freight trains.
For that reason, RTD will use heavier commuter-rail trains for FasTracks corridors it will share with freight carriers, including the line to Denver International Airport and the Gold Line to Arvada/ Wheat Ridge.
The Union Pacific Railroad recently told RTD it would have to spend $6 million to $7 million on train protection walls to separate UP freight trains from commuter rail cars at key points along the Gold Line route, said Ashland Vaughn, engineering project manager for the commuter rail project.
Similarly, RTD will have to spend up to $8 million on protection walls separating UP freight trains from DIA-line commuter trains at points where they will run closest to each other.
Jeffrey Leib, The Denver Post
