Why are painted road markings (pasos de cebra, flechas viales) and metal manhole covers (tapas de alcantarilla) particularly dangerous for motorcyclists in wet weather?

1. They emit magnetic fields that stall the engine
2. When wet, paint and smooth steel have near-zero friction, causing instant tire slip if a rider brakes, accelerates, or leans over them
3. They cause tire rubber to dissolve chemically
4. They reflect sunlight and blind the motorcycle battery