To set a route, simply follow these steps:
Locate and click on the signal to which you want to set the route to; the flashing cursor will disappear and, if the route is allowed to be set, then a white line will appear along the track from the start to the finish of the route. A short section of track beyond the exit signal is also usually set: this is the overlap - a safety margin for overrunning trains.
If the route is into a dead end (platform or siding), click on the grey arrowhead at the end of the track. If the route crosses a break in the diagram, you may have to find the next signal after the break, or there may be a grey arrowhead that acts as a copy of the signal.
The stem of the signal symbol (the L-shaped bit that was grey) will change to white to indicate that a route is set from the signal, and the entry signal aspect (colour) may change to a less restrictive aspect depending on the state of the route ahead. If one, or more, sections are clear with routes set (manually or automatically), the signal aspect may change to Y, YY, or G. However, if the signal is Approach Controlled, it will only change as the train approaches the signal.
Where there are facing points beyond the exit signal, there may be more than one possible overlap. In this case SimSig will normally select one automatically, changing it if subsequent route requests require. The message “No Overlap Available” means that the route can't be set because, although the main route is clear, none of the potential overlaps are available. If it is not obvious why, the page "No overlap on some forward routes" may be able to explain.
Note that signals with the letter “R” (or “RR”) beside them are repeaters. Ignore these for the purposes of routesetting and instead select the next signal which does not have an R beside it.
Also note that, for trains in passenger service, routes should normally only be set between main signals, not to shunt signals.
You may wish to cancel a route, perhaps because you set the wrong route, have changed your mind, or whatever. One thing you should remember: train drivers do not like having a signal go back to red in front of them, particularly if they are moving at 125mph! To them it means that there is an emergency and they must stop the train as quickly as possible.
Okay, so you've weighed up the advantages and the risks, and you still want to “pull” the route. If you right-click on the entrance signal for the route you wish to cancel, a standard Windows menu will appear with several options. The option you want is the top one, Cancel Route. If there are no trains approaching, the signal will go back to a red aspect, the stem of the signal will revert to grey, and the white track will also revert to grey.
However, if a train is approaching the signal, then the route will be ”approach locked”. The signal aspect will flash red (it appears solid red to the driver) and the route will only be released after a time interval, generally two minutes.