Model railroad switches, just like real-life railroad switches are used to route rail traffic. In model railroading, switches are most commonly referred to by the technical term "turnouts". In the UK rail switches are referred to as "sets of points". or just "points". This is because the moving rails within the switch are called points. Trains enter turnouts by a single track and can be routed to either of two, or sometimes any of three, exiting tracks.
Turnout Settings: Closed or ThrownIf you want the train entering a turnout from the single track end to continue in its current direction the switch is closed; but if you want it to diverge in another direction the switch is thrown. Some turnouts are curved.
Left and Right Turnouts
Two way turnouts come in left-hand and right-hand varieties, where left and right are the direction a train entering from the single track end of the turnout diverges when the switch is "thrown". The photo shows common left and right switches, or turnouts.
A few manufacturers of model railroad track offer curved turnouts. In the case of curved turnouts the if switch is closed the train continues on the curve's current radius, and if the switch is thrown it turns onto a curve of a tighter radius.
A turnout's number expresses how much it will cause a train to diverge when it is thrown. The number is calculated by taking the number of units of forward travel for one unit of divergence. For example, if after traveling six inches from the point of divergence the train has diverged one inch, then you have crossed a #6 turnout. A rule of thumb is, the smaller the number the tighter the radius of the turnout's curve. The image shows, a #6 right turnout and a #4 right turnout. Notice that the #4 turnout diverges much faster than the #6.
A wye turnout has no straight exit track. It has exits that turn to both the left and right. I suppose a wye is never closed, only thrown left or thrown right. But I've never actually read any references that discuss the matter. If anyone knows for sure, please write a post in our forum. Please include a link if you know an online reference.
Three Way Turnouts
In the unusual case of a three-way turnout, the switch can be thrown left, closed, or thrown right. Three way turnouts are a kind of exotic item. They aren't made by a lot of track manufacturers. Marklin, Peco, and Shinohara are the only manufacturers that I know of who make them. However, the Peco three way has right and left turnouts slightly offset in one piece of track, instead of all three paths diverging at the same point.
A special kind of turnout is a "crossover" turnout. A crossover turnout allows trains on one track to continue straight or cross over (diverge) onto an adjacent parallel track. A "double crossover" allows both parallel tracks to diverge onto each other. The photo shows a double crossover.
Double Slip Switch
A double slip switch is similar to the double crossover discussed above. However, it has no straight tracks. Instead if has two tracks that cross over, but can be switched to curve back to the side of the crossover they came on, instead of continuing on a straight path.