Which part of the railway? There are a few places where you can "reach" it. I know of 3 locations.
1 is at the end of Railway Mall, where the railway runs over the bridge crossing the main road. There's a slope that leads right up to the track without any fences.
Another 1 is near King Albert Park, where there's a dirt track that leads slightly uphill along the track and there's a train station or something there. No fences but there's a security guard or something at the station.
The last one i know is at rifle range road.
Hope this helps.