Railroading 101
Bob Ciminel
Founder and Moderator – Montour RR and PRR Panhandle PA Discussion Groups
Part 2 – Switches

We call them switches, but the correct term is turnout.  Their function is to allow a train to move from one set of tracks to another set of tracks without derailing.  The key to the turnout is the frog, which allows the wheels on one rail to cross to another rail.  The term frog came from the fact that the device looks like the legs of a frog.  
The frog determines the number designation for the turnout, which is determined by the angle of the crossing rails.  For example, on a No. 11 turnout the frog diverges 1 foot for every 11 feet of length.  The allowable speed over a turnout increases as the number increases.  Low-speed turnouts (15 mph or less) are used for yard tracks, industrial tracks, and hand-thrown main track switches.  A Number 11 turnout is considered a low-speed switch.  Moderate speeds can be run (25 to 50 mph) over turnouts numbered between 14 and 24, which are typically found on power-operated main track switches.  High-speed turnouts, such as those used on the Northeast Corridor between New York and Washington, are Number 30 and higher and can be transited at 70 mph or higher.
The major parts of a turnout are the stock rails, closure rails, points, frog, and guard rails.  The stock rails are the outside rails of each route through the turnout and do not move when the switch is thrown.  The closure rails are the moveable rails for each route and end in tapered points that fit against the stock rails to force the wheels onto the new route.  The frog guides the inner wheels on to the selected route and the guard rails ensure the wheels stay on the selected rails as they pass over the frog.  The only other major components are the switch stand and operating rod.  The switch stands are usually equipped with a target or a banner to show the turnout’s alignment.  Green or white indicates the turnout is aligned for straight-away movement; a red light or red marker indicates the switch is aligned to the alternate route.  For verbal communications, a switch is either normal (green) or reversed (red).
For operating personnel, there is a procedure for aligning manual turnouts that is generally followed by most railroads.  First, the turnout has to be unlocked.  Any turnout that leads into our out of a main track is required to be physically locked.  The lock is usually a key-operated hasp lock.  After unlocking the turnout, the device that holds the operating handle in place is opened and the turnout is thrown over to the alternate route.  The switchman then verifies that the closure rail points are properly aligned against the stock rail and re-locks the switch in the new position
Another important term when discussing turnouts is the fouling point.  This is a point near the frog where equipment on one track could strike equipment on the other track.  On some railroads, this point is marked on each turnout.  A quick determination of whether a car on an adjacent track is fouling the other track is to walk with your foot against the inside rail and hold your arm out.  If it touches anything on the adjacent track, the track is fouled.
Turnouts are also designated as facing point or trailing point.  If a train is moving toward the switch points, it is a facing point.  If the train is moving away from the points they are trailing points.  If a train approaches a switch that is not aligned for straight-away movement, the switch is “lined against the movement” and the train will take the diverging route.  A trailing point switch not aligned for straight-away movement will usually not derail a train; however, the switch is considered to be “run through” and damaged.  Damaged switches are “spiked” to hold the points against the stock rail until the switch can be repaired, but they are considered out of service.
Types of Turnouts
Most turnouts have a tangent (straight) route and a diverging route, and are commonly referred to as right hand or left hand turnouts when facing the frog.  These are usually found at entrances to sidings, spurs, or branches.  A second type of turnout is called an equilateral turnout, which has no tangent route but instead has two diverging routes that go off at equal angles.  An example of this type of turnout would be where a single-track line becomes double-track.  A third type of turnout is called a crossover, which allows trains to move from one track to a parallel track.  These are commonly found on all double-track lines.
 (Reference: Elements of Train Dispatching, Volume 1 by Thomas White, VTD Rail Publishing, Mountlake Terrace, WA, 2003)