Set the turnouts

Set the turnouts, send the train off, then throw a turnout again while the train is rolling in. The track field works like the block plan of the software.

Ready. Set the turnouts and send the train.

Tip: occupy track 3 with a parked train, then try to switch to it. Turnouts also work with the keyboard (Tab, then Enter or Space).

What you are seeing

Reservation
Before the train reaches a block, it is reserved (yellow). Only when the train is inside is it occupied (red).
Switching on approach
Even within an already reserved route you can still throw turnouts, as long as the new direction can be reserved and there is enough time before the train arrives to set it safely. The old reservation is released, the new one applies at once. If the new route is occupied or the train is already too close, the engine rejects the request.
STOP
STOP halts all trains at once, RESTART releases them. In the software STOP sits on F12 and is always visible.

This is a simplified imitation in the browser, not the software itself.