The starting point railway station ? its at Kepple Road ... google Tanjong Pagar Railway Station for the map
The rest of the track cuts Singapore in half........and winds from southern Singapore to the northern tip at Marsling with 6 to 7 known access points by foot
Kg Baru Road has access next to the old old 3-4 storey HDB blocks next to St Teresa church
or from Lower Delta Rd towards Sentosa you will drive over it from an overhead bridge
Bukit Timah Rail Mall (google it for directions) is a popular but dangerous stretch on both sides of Bukit TImah Rd near Diary Farm area
Another spot is near the Kranji War Memorial where you take the road towards Kranji Resevoir and Sungei Buloh Wetland Nature Reserve ...... the road will go OVER the actual tracks ..... park somewhere safe nearby and go by foot
Otherwise PM the guys who have shot at locations that you like and ask them for directions
p/s Aiyoo ....... just google Tanjong Pagar Railway Station and click on the streetdirectoryasia link ..... it IS interactive.... keep dragging the map on the screen and following the black and white line and see what roads or access points
like i said above.... drag the interactive map and keep following on it on the screen....... examine it CAREFULLY... the map shows when it goes UNDER a bypass or bridge (almost always) or OVER a road via a bridge (HINT Rail Mall area ) .....
Thats the bridge the train uses dedicated to the trains that i know of..... the bro' below has shared another one at Sunset Way at Clementi
careful..... this bridge has taken a few lives already in the past..... its a dangerous stretch with nowhere to run except straight in the opposite direction if a train comes along
goto tanjong pagar mrt/outram mrt, tell e taxi uncle u wanna goto the railway station..
if u'd like us to tell u how to go the "the bridge in the thread i saw", it would be instrumentive to show the thread..
or ask the fella who shot the photo in that thread..
I doubt a scenario such as the one that you had described will ever happen as the last train had long rolled past the bridge decades ago. Trespassers are more likely to fall through the corroded metal plankings or between the decomposing wooden railway sleepers into a possible certain death below.