The remains of Bristol's docks railway include a section in front of what is now a museum (originally a harbourfront warehouse) where the tracks are open to pedestrians and cyclists but not motor vehicles. The rest of the railway tracks are completely off-road, trains only. Several cyclists have had serious injuries getting wheels stuck in the tracks or slipping on them, and one or two have even died (from falling into the docks and drowning). Many more, including me, have had non-injury incidents there (wheel got stuck but immediately popped out). So much so that cyclists are now heavily dissuaded (but not, I think, legally banned) from using that section and an alternative route has been made (round the back). I also recall an occasion when two cyclists of a group I was in were injured, one seriously, in falling on disused tracks at Sharpness docks, with no other vehicles anywhere near. So I think rails can be a problem without any traffic pressure.