Your typical location might place you on the route bus drivers use to return to a depot or to get to the start of a popular route. Or the time you're out and ab

Your typical location might place you on the route bus drivers use to return to a depot or to get to the start of a popular route. Or the time you're out and about might coincide with when a large number of busses are coming into, or going out of, service. For example, if you work offset hours you'd easily see the pre or post rush hour ramp up/down traffic. Out of service busses also travel faster than in service ones; as you note, you outpace busses on your bike. Perhaps look up research instead of relying upon personal anecdotal observations by one person in one city, subject to observational biases? The research is likely to be highly accurate given most public bus operators have very good data about ridership numbers and fuel use per vehicle and route.