Rolling very slowly, trying to avoid unclipping as I approached a pedestrian crossing, I went across a roadside culvert. Nothing wrong in that you say - well, there was a slot in it, just wide enough to fit my front wheel.
The wheel stopped, and I had time to see it buckle as all my weight fell over it.
I hadn't been aware that hazards like this might be placed in the road.
The result - trashed wheel - lucky it was the winter training wheel.