I find it useful to do this....
In the "With Train" part of a route file, list all your trains, and simply comment out with semi-colons the ones you don't want to run... like this...
with Train
.Folder cl158
;.Folder ONE_class156
;.Folder 37901 Empty Steel Carriers
;.Folder HST4
;.Folder Voyager
which would run the route with the 158 DMU..... move the semi colons around like this...
with Train
;.Folder cl158
;.Folder ONE_class156
;.Folder 37901 Empty Steel Carriers
.Folder HST4
;.Folder Voyager
and it runs with the HST.....
So, before running the route, open it in something like Notepad and edit those semicolons, save it, and away you go.....
If you wanted, you could make your own timetable bitmaps for each type of traction, then find the timetable line, add one for each train, and comment them out as above...
... hope that makes sense.