In classic crime stories, someone calling you a “double crosser” was a bad omen. It might indicate … a rough road ahead, to say it one way.
In subway stations, however, having a double crossover allows trains to adapt to changing conditions.
Case in point, the Purple Line (D Line) Extension Project.
A crossover is a pair of switches connecting two parallel rail tracks, allowing a train on one track to cross over to the other. A “double crossover” allows both trains to change tracks, which Metro Rail Operations thinks is a very good idea. No wonder that each Metro Rail line has several crossovers, including our subway extension.
Let’s say an obstacle appears on the westbound track — maybe a pink unicorn or a train having an issue. The westbound train could use the double crossover to switch to the eastbound track and leave the unicorn unbothered. A double crossover switch can be thrown remotely from the Rail Operations Center (ROC), onsite from a Local Control Panel, or even by hand from the switch machine itself on some lines.
Technically, the double crossovers in the La Brea and La Cienega stations are “guarded,” meaning a second rail at the switch offers protection that the trains stay on the track and allows them to crossover at higher speeds.
The La Brea and La Cienega stations are approximately 200 to 300 feet longer to accommodate the crossovers, although crossovers vary in length. The longer the crossover, the faster a train can be traveling when it switches from one track to another.
The crossovers are necessary — and also make an already complex project even more complicated because of the station lengths and accomodations that need to be made for the switches.
Fish bolts and fish plates are essential parks of the crossover system, as are frogs, but not the amphibian variety. (Fish plates hold two rails in horizontal as well as in vertical planes at equal height.) Frogs direct train wheels to cross from one track to another.
Crossovers are not limited to subways. They are used around the world on above-ground passenger and freight rail lines. Crossovers are one of many specialized pieces of equipment that Metro Rail Operations continually inspects. Metro dedicates entire crews to maintain these specialized tools.
If you are a model railroad enthusiastic, you can purchase crossovers. If you favor LEGO trains or have wooden Thomas the Train tracks, you can also build a crossover.
Categories: Transportation News