There are numerous non-loco hauled trains within the game, these are "not required for red penning" and do not give any mileage bonuses. There is an option within the game's options screen to turn off notifications about non-loco hauled services. The following classes of unit are available to travel on in-game.
There are also some alternative methods of transport, no mileage is recorded for using these alternatives however using the Bus or Taxi will incur a points deduction, using the Tube and Walking are both free options though have a longer journey time.
BUS No Mileage is recorded 10 points per mile cost
Taxi No Mileage is recorded 30 points per mile cost
Tube No Mileage is recorded
Walk No Mileage is recorded
Tram NO Mileage is recorded