Comment by grues-dinner

Bus Rapid Transits can operate at frequencies of about 10 seconds per bus. Obviously they're highly parallelised to achieve that and have special infrastructure to enable it like dedicated stations and pedestrian access, so it's not just "a bus", but bus-based systems are how many of the very highest-throughput public transportation lines function, with up to 35000 people per hour per direction with three digit numbers of buses per hour.

For comparison, the most frequent London underground service is 100 seconds per train and the system moves about 50k passengers an hour (based on a 21% increase representing 10k passengers, I couldn't find a direct figure), presumably that being both directions.