From Definitions, p. 8, The Consolidated Code of Operating Rules:
"Centralized Traffic Control System. (CTC) - A block signal system under which train or engine movements are authorized by block signals whose indications supersede the superiority of trains for both opposing and following movements on the same track."
This definition is about all a train or engineman needed to know about CTC. The system was quite simple: observe the signal, consult or memorize the signal chart, and "be governed accordingly." For those operating exclusively in CTC, rules exams were redundant.
pix CTCmerge caption: Burlington Northern Signal Aspects and Indications Feb 1, 1977 - Director Signal Engineering St Paul
Third Sub CTC Control Points
MP 49.5 Wabash
MP 52.5 Centralia East
MP 53.9 Centralia Center
MP 55.8 Centralia West
MP 58.6 Chehalis Jct.
MP 66.2 Napavine
MP 77.0 Vader
MP 85.0 MP 85
MP 93.5 Ostrander
MP 98.9 Kelso West
MP 102.5 Longview Jct. West
MP 110.9 MP 111
MP 123.6 Ridgefield West
MP 132.5 Vancouver Jct. East
MP 136.0 Vancouver
It was a relief to leave the "turkey trail" and enter the B.N. Third. Once established on the Third, it was sit back and enjoy the fast ride. The dispatcher did all the work; and without train orders. No meets, no lining in and lining back, no flagging, little thinking. And because each of the four railroads which used this road had their own distinct radio frequencies, the railroad scene was always a surprise. Suddenly we were crossing over to clear Amtrak #796; or going around a B.N. setting out at Longview Jct, or switching mains because the U.P. we were following just lost its air. On Milwaukee trains we were usually unable to get by Rocky Point (Kelso) without work. It was convenient to have it on the dispatcher to get us into position for Rocky Point, and have it on the dispatcher to flag for us while there. How much better it would have! been had the Milwaukee used this route all the way into Tacoma.
But with an excess of 50 trains per day, operated by four different companies, running on the Third, when things went wrong, watch out. For much of the summer of '77, the Third was reduced to single track operation at the Columbia River Draw at Vancouver. This was because a fire had damaged the bridge deck. While they replaced the ties on one main, trains in both directions operated on the other. Meanwhile trains stacked up on both sides of the bridge like a World War Two movie, in which the Allies had bombed out the bridge. The exception was first class trains, which ran around the freights waiting on the bridge approach. Train crews dropped dead one after another in this mess. Rested Milwaukee crews in Portland often had to dog catch their brethren at the Columbia River Draw.
pix: CTCtrainmerge caption: L. Top: View South, Columbia River Draw Middle: View South, MP 85 R: View South, Napavine Hill
L. Bottom: View South, Entrance to CTC at Chehalis Jct R.: View North, Chehalis Jct