A little earlier on today I posted an item about oil slicks, or rather their lack of them if you cycle on cycle paths instead of roads.
The discussion in the comments on that post moved on to the problem of leaves on cycle paths and roads creating difficult and dangerous conditions for cyclists. Of course, cycle paths are swept regularly here in Assen.
Here's a photo of the end of a cycle path in the city, where cyclists turn onto a minor road. You can see from the continuation as a walking route on the other side of the road how it might look by now if not for the regular sweeping. The corridor of trees is the same on this side of the road. Actually it's probably thicker. You can make up your own mind by looking at a view in the opposite direction from the same point.
It's essential to have good maintenance of cycle paths if they are to encourage people to cycle.