Electropneumatic interlocking plants still govern the movement of trains, and WMAQ reports on an important one at the hottest hot spot of the Metra system.

Lots of good block bell and lever action sound effects.


David Foster said...

Interesting. I would have thought these high-traffic commuter systems would all have gone to CTC many years ago

Stephen Karlson said...

Think of an interlocking tower as a local Centralized Traffic Control system. The train director works with the yardmasters and dispatchers to move trains expeditiously from yard limits (under the control of the yardmasters) to main tracks (under the control of the dispatcher). Further complicating things, the trackage east of Western Avenue is under control of the Amtrak dispatcher on the Milwaukee side, and Commuter Control on the C&NW side. West of Western Avenue, two additional dispatchers control the traffic. The CTC begins on the old Milwaukee and on the old North Western to the west.

Sometimes, reworking an interlocking tower to work with CTC is not cost-effective. The most notorious example is the Zoo Interlocking in Philadelphia, quite the head-scratcher for the techies putting Amtrak's CE&TC (E = Electrification) in place.