I presume that you mean a four platform terminus.
The simplest way is to have a facing crossover and a trailing
crossover in your double track throat of the terminus, then have a
point in each road to provide for the four platform roads. This
formation will allow any platform to access any road, and vice versa.
If you're short on space, then you can combine the facing and
trailing crossover into a scissors crossover.
If you're really short of space, you can combine the two points into
the platform end of the scissors crossover and make two double slips -
getting a bit complex now :-)
However, other factors might affect how your station throat is laid
out - such as where your MPD is. If it is close to the station, then
locos will probably want to access most, if not all, of the platform
roads to and from the MPD. The situation of coach storage and/or
cleaning roads can also affect the layout of the throat if there is
going to be a lot of movements to and from them.
Another thing to watch out for is that you can get more than one train
through the station throat for most routings. It's not going to
allow very efficient programming if every train movement through the
throat blocks off every other possible movement in the station.
Then of course, you could do away with the facing X over, down main to up
main, and use the down platforms, 3 and 4, for arrivals and the up
platforms, 1 and 2, for departures. But that's not what you asked for.
In response to requests.......
1 ____________________ Run around ___ PY
\ ____________ /
2 _____________________\_________/____________\____/____ LR ___ Up Main
3 ________________________/_\_______________________________/___ Dn Main
4 ____________________/ / Sea wall
P = Ponsandane Yard carriage sidings
L = Longrock loco depot (PZ)
For modelling purposes you could go back to something like the GWR track
layout with a few minor changes to improve operation.
1 ____________________ Run around ___ Carriage sdgs
\ ____________ /
2 _____________________\_________/____________\____/____________ Up Main
3 ________________________/_\___________________________________ Dn Main
4 ____________________/ / Headshunt/goods yard
______________/_/_ _ _
___________/ (Turntable if desired)