Introduction 5 Chapter One: Crossings 7 Chapter Two: Where lines meet 17 Chapter Three: Interlockings 23 Chapter Four: Tower operations 33 Chapter Five: Interlocking signals 39 Chapter Six: Modeling interlockings 55 Chapter Seven: Interchange traffic 73 Chapter Eight: Junction details 79 COTETS
1-22 Backdrop Minnesota Transfer Peninsula ew Brighton ST. CROIX, MI. Soo Line the setting. Figure 1-20 shows two ways to hide staging areas along straight stretches of your layout, and ways to use hidden track to link interchange areas. An alternative is to continue the junction and interchange tracks onto a peninsula into the room. One way of doing this is shown on Bob Rivard s HO Soo Line in fig. 1-21. Bob modeled the Soo Line s ew Brighton, Minn., crossing with the Minnesota Transfer by extending the MT line onto a peninsula in the front of the layout (fig. 1-22). You can do this to any extent, carrying the peninsula a few feet or extending it to fill your space. Abandoned crossings Far fewer junctions are in service today than in the steam era. This means that a lot of track has been abandoned at former junctions. Modeling a bit of abandoned right-of-way can make an interesting scene that need not take up much space. Railroads generally remove the diamond itself as soon as a crossing track is abandoned, wanting to get rid of the maintenance headaches of a crossing as soon as possible. Yet the neighboring rails can remain in place for years with weeds and brush slowly overtaking them. As the photos show, signals and other hardware often are left in place as well. Sometimes nearby track remains in use, and what was once an interchange track becomes merely an industrial spur. At other locations, the right-of-way will be bulldozed for a different use on one side of the former crossing, while abandoned rails lurk in weeds on the other side. Use your imagination to add scenes like this to your layout. The rails of this Conrail branch are in place, but the diamonds have been removed. The active track belongs to the Ann Arbor in this 1976 scene at Federman Junction, Mich. John Uckley The diamond is gone where the abandoned Milwaukee Road line once crossed the Soo Line in Burlington, Wis. The home signals that once guarded the crossing were abandoned in place. Jeff Wilson 16
Where lines meet 2-1 Many junctions don t involve tracks crossing at a diamond but instead feature two (or more) routes meeting. This can involve a branch line joining a main line, a main line splitting into two divisions, or a junction between two railroads as fig. 2-1 shows. Some are very simple, with just the joining of two tracks, but others are quite complex, with multiple sidings, a full wye allowing traffic to move in all directions, or a small yard. All of these can provide numerous modeling possibilities. And, as with diamonds, these locations can be modeled as full working junctions or with one or two dummy tracks that extend to give the illusion of a working junction. The Chicago, Burlington & Quincy (two left tracks) joins the Illinois Central at Portage Tower, Ill. In this 1966 view, the westbound CB&Q passenger train is about to enter IC tracks, where it will run via trackage rights north of the junction. Mike elson TWO 17
Centralized Traffic Control 3-19 A dispatcher operates the CTC panel controlling the Union Pacific s Las Vegas-Yermo subdivision during World War II. Union Pacific Centralized Traffic Control, or CTC, was a close relation of the all-relay interlocking control systems of the 1920s. Electric control of turnouts and signals enabled an operator to control several points from a central or remote location (fig. 3-19). The first CTC application, installed by General Railway Signal Co., was on a 40-mile stretch of the ew York Central in Ohio in 1927. By the late 1930s, CTC was being used to control much longer stretches of track. A CTC-controlled line is basically a series of interlockings. Each end of a passing siding, or each junction, is called a control point (CP) or OS section (for on-sheet), with signals and switches controlled by the dispatcher. Automatic block signals (controlled by track circuits, not the dispatcher) are located between control points. This lets the dispatcher control trains by signal indications, eliminating the need for train-order operation. CTC prevents a dispatcher from aligning conflicting routes. Figure 320 shows the basics of CTC operation. The top of the board has the track schematic, including occupancy lights (white for blocks, red at control points). All switches and signals are numbered from left to right: odd numbers for switches, even numbers for signals. Levers below the diagram control switches (top row) and signals (bottom row). The switch levers can be turned to the left or right and are labeled and R for normal and reverse positions. ormal means set for the main line, and reverse is thrown for the passing siding. Red lights indicate the switch position selected. The signal levers have three positions: straight up (all signals red) or to the left or right ( L and R ) for trains running to the left and right according to the track schematic. If the lever is straight up (the normal position), the red light above the lever will be on; if thrown left or right, the corresponding green light will be on. 32 How it works In fig. 3-20, the dispatcher has changed switch 21 (at the right end of Baker siding) to the reverse position to route the train coming from the right into the siding. Signal lever 22 is flipped to the left, which lets the signal tell the train that it is entering the siding. The dispatcher sets the levers, then pushes the code-start buttons below those switches. The route is checked for conflicts, and, if there are none, the switch and signals align. The remaining switches and signals are positioned to let the other two trains which are moving from left to right hold the mainline. Operation of the all-relay interlocking board in fig. 3-14 follows the same methods. Following World War II, CTC became the dominant method of controlling busy main lines. Today s systems use computer software and video screens instead of mechanical levers and relays, but system operation is similar. CETRALIZED TRAFFIC COTROL (CTC) CTC field installation Dual-control turnout motors may be manually operated for switching ABLE Block OS section BAKER Intermediate signal (automatic) CTC machine based on Union Switch & Signal Co. style Track layout with mileposts 38 39 40 ABLE 41 16LA 15 18L 16 White lamps for block occupancy 17 18 Set for train through Able from left to right 3-20 20LA 22RC 20R BAKER 44 45 20LC 16LC 18RA 18RC 43 Traffic lamps light to show direction cleared on single track Track model with occupancy lamps OS section 16R 42 Red lamps for OS occupancy Switch levers with lamps showing normal () or reverse (R) position of switch points in the field Signal levers, with lamps showing signal cleared left or right (green) or no signals cleared (red) 20 Code-start buttons levers are first set for desired movement, then button is pushed to transmit coded commands to field location 22L 22RA 19 21 22 Set for meet at Baker
Tower operations 4-1 The last chapter described the mechanics of how interlockings work. ow let s take a look at how tower operators did their jobs, and how they determined which trains to route on which tracks. Tower operators were responsible for guiding trains through the various routes available at an interlocking plant and prioritizing trains through crossings. In many cases, the operators had to decide how do this, but in other cases they received their cues or directions from dispatchers of the railroads whose tracks were controlled at the tower. Interlocking towers often controlled tracks of two (or more) railroads, but the operator was generally an employee of one railroad sometimes the busiest line, sometimes not. Although operators did their best to get all trains through a plant expeditiously, the host railroad s trains received preferential treatment if schedules were tight. The operator hoops up orders to the engine crew of an eastbound Illinois Central freight train at Portage Tower. The two tracks to the left belong to the CB&Q. Mike elson FOUR 33