However, busses and trains usually only run every 10-20 minutes compared to a road which is going constantly. I can easily see cars on roads having higher throughput.
The intercity trains, when in a maximum length 6+6 car configuration of 2-floor trains, can carry over 1200 (sitting!) passengers. That's as much as a single lane of road can carry in half an hour with average car occupancy (low). So running such a train every 15 minutes should give a similar capacity to a free-flowing road with 2 lanes, while needing less room for infrastructure. Plus people mostly go to the station by foot, bike or bus rather than car, which is also nice capacity-wise and pollution-wise.