ideas on how to get time of journey back without the station

[l_Blue_l]

OK this is just ideas and i cant work out how i would code to get the time of a journey back to the loading station without arriving at the station (this is becasue i want the time of the journey and not the time waiting outside the station aswell). i want this to be as foolproof way as possible of getting the time of a trains journey but i have only come up two workable idea:

add a new type of waypoint to get the time of the trains journey.

i dont like this idea becasue it isnt fool proof becasue the user has to set this up.

i did think about useing the pathfinder YAPF to do this but what do i check for if i am within 20 rail tiles of the station do i stop the timer but what if there is a large que of trains or even just one very large train in the way. what happens then.

This has been on my mind for the past 3 hours and i havent come up with a foolproof way of dooing it. If you have any ideas i would love to hear them.