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Monday, September 8, 2014

TWC/ABS on the California Coast Line

So here is a little video example of how signaling works on a North American line with both Automatic Block and Track Warrant control.  Out west this is simply called TWC / ABS although in some parts of the east it is known as Rule 271.  Basically this is where block signals keep trains from colliding, but track warrants keep them from conflicting.  Previously trains would rely on the timetable and train order system to sort out who had priority on a single track main line, but since the advent of radio the dispatcher can just tell trains what he would like them to do directly.

Number plate? Check.  Hand throw switch? Check. Semaphore? Optional.

This line is the coastal route between San Francisco and Los Angeles comprising parts of the Coast and Santa Barbars subdivisions.  Because of the lack of through freight traffic the line has seen minimal investment from Union Pacific.  When recently the old pole line and searchlight signals were removed, UP declined to pony up for a CTC upgrade with its attendant interlockings and traffic control.  So while the signals are the typical type of LED Darth Vader with PTC antennas, crews must still copy down train orders and get out to hand throw switches for meets.

In this case upon leaving San Luis Obispo our train was issued a Track Warrant to a point called DEVON (which the crew insists on pronouncing incorrectly in the video).  Later we got another Track Warrant to proceed from DEVON to Santa Barbara, however the later would not enter into effect until we met a northbound UP freight train at DEVON and he took the siding (GCOR rulebook Box 5). 

The meeting point was well chosen as we arrived just as the opposing train was passing the automatic signal directly to the south which was indicating Approach.  Our train's conductor climbed down to the right of way and lined the hand throw switch for the freight train to save a little time, then returned it to the normal position so that we could proceed.  The fact that the freight train had more engines than cars indicates one of the reasons there has not been much investment in the line. 

Here's the thing.  While this is still all quaint and manual and worth filming as a quasi-historic railroad operating practice...without the pole line an searchlights this is basically just delaying my train with little value added. 

If you want to travel this line and check out the new old signaling there is a daily Coast Starlight round trip covering the TWC/ABS segments on both subdivisions as well as a Pacific Surfliner day trip option from Los Angeles to San Luis Obispo.

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