are you looking for the railway station or the tracks where some do their model shoots?
The railway station is at keppel, you can get there via the buses mentioned, or have a short walk from outram/tanjong pagar MRT
if the tracks, you can head to bouna vista (note: it's still in use till end of the month, so becareful of the trains), or the abandon tracks at bukit timah
erm, there is one near sunset way block 109... then across the basketball court, you just climb up the bushes to the tracks... it has been abandoned so no worries that there will be train honking you halfway through out your shoot...