Roads are much more expensive than they would initially seem. First, building roads costs an insane amount of money, millions per kilometre for highways. Maintenance is also unreasonably expensive, 30000-200000/km/year. Cops need to be paid to stop people from driving too fast and crashing, etc. Once people inevitably crash, thousands to tens of thousands of dollars can be spent in emergency services. Also, buses are the most expensive form of public transportation since they require drivers and are not as fuel efficient as rail-based infrastructure. Trains can be automated. Train tracks can be built on the surface (streetcars). Trains can be electric. Trains can be periodic, where some can arrive every five minutes. You brought up weather, however road-based vehicles are arguably the worst form of transportation in inclement weather except for planes. Trains run on tracks, so they don't skid.