Fallen leaves on train tracks can be incredibly slippery, posing a significant safety hazard for trains. This slipperiness is caused by several factors, including:

1. The smooth, waxy surface of leaves. Leaves are covered in a thin layer of wax, which makes them smooth and slippery. This wax also prevents water from being absorbed into the leaves, making them even more slippery when wet.

2. The small size of leaves. Leaves are relatively small and flat, which means that they can easily get caught under train wheels. This can create a barrier between the wheels and the tracks, reducing traction and causing the train to slip.

3. The weight of leaves. When large piles of leaves accumulate on train tracks, they can add a significant amount of weight to the tracks. This can cause the tracks to flex and buckle, which can further reduce traction and increase the risk of a derailment.

4. The moisture content of leaves. Wet leaves are much more slippery than dry leaves. This is because water can dissolve the wax on the surface of leaves, making them even smoother and more slippery.

5. The temperature of leaves. Frozen leaves are also very slippery. This is because the ice on the leaves can create a barrier between the wheels and the tracks, reducing traction.

To mitigate the risk of accidents, railways often use a variety of methods to remove leaves from train tracks, including:

* Sweeping and vacuuming: Railways may use brooms or vacuums to remove leaves and other debris from the tracks.

* Chemical treatment: Railways may use chemicals to dissolve the wax on leaves, making them less slippery.

* Water jets: Railways may use water jets to wash leaves off the tracks.

* Leaf blowers: Railways may use leaf blowers to blow leaves away from the tracks.

* Vegetation management: Railways may cut back vegetation near the tracks to reduce the amount of leaves that fall onto the tracks.

These methods can help to improve traction and reduce the risk of accidents caused by fallen leaves.