Look at slide 39 and following, where they discuss the pilot of a "screening car" that pax have to pass through when they get on the train.
* Shoreline East Commuter Rail passengers to be
screened for primary explosives threat after boarding
while train is enroute to next station
* All passengers from each station must either be
screened or bypassed before reaching next station –
typically a five minute screening period
What's the point?!?! They're already on the goddamn train at that point! They can blow it up if they want before they get to that next station. This makes about as much sense as beginning to screen people after a plane has reached cruising altitude and the captain has turned off the no seatbelts/start screening sign.
Actually the whole train screening program makes about that much sense.