The iconic London ‘Routemaster’ bus which first entered service in 1956 seated 64, and carried many more with standing passengers, I’m sure other readers can point up genuine capacity of their buses within their cities. Once the cities reach 1-1.5k and the programme starts spamming you with traffic jams around 1990, the capacity of the featured buses really need to go to actual genuine capacity.
With just 7 cities on the map, without full coverage in any of them, I still have 250 buses, none of which are matching demand, and in two cities the buses were constantly getting grid-locked (cannot move as a bus is attempting to turn left into a complete queue of buses behind it that stretches past where the left turn is), I gave up completely with one of the cities and retired all the buses on the 4 routes within it. The automatic spacing doesn’t help either, at all; late game, it becomes a hinderance. Traffic giant at least allowed you set spacing if you wished, for each tram or bus on every route.