oh I can explain leaves. In the UK during the age of steam (basically before 1968) embankments and cuttings were kept pretty clear of foliage as they could be set on fire from flying sparks. Steam trains also needed sandboxes for grip up hills as it was hard to work two locomotives in tandem. When diesels replaced steam locomotives they thought they didn't need to worry about foliage nor sand grip as the diesels didn't produce sparks and could be connected to work from one cab. Unfortunately this has led to the leaves problem as leaves when wet can get greasy and slippery. It may be the same with the millipedes (squash a load of millipedes and that must leave a greasy smear on the rails)
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oh I can explain leaves. In the UK during the age of steam (basically before 1968) embankments and cuttings were kept pretty clear of foliage as they could be set on fire from flying sparks. Steam trains also needed sandboxes for grip up hills as it was hard to work two locomotives in tandem. When diesels replaced steam locomotives they thought they didn't need to worry about foliage nor sand grip as the diesels didn't produce sparks and could be connected to work from one cab. Unfortunately this has led to the leaves problem as leaves when wet can get greasy and slippery. It may be the same with the millipedes (squash a load of millipedes and that must leave a greasy smear on the rails)