At the very least, I would assume most bus time tables are written to reflect the worst case scenario regarding traffic lights. That alone should make the actual average waiting time lower than the theoretical one.
Where I live, buses have a few points where they 'synchronize'. That means they wait there long enough to be exactly on schedule.
This to prevent people missing a bus that goes every hour because it was 5 minutes early.
The "El" (Elevated) trains in Chicago will do the same thing. Sometimes you simply stop between stations. Sometimes, it is only 25 ft before a station and you can see your goal in sight.
Why would they stop for regulation (as opposed to the track in front being occupied, which is obviously a good reason to stop at any place) at anything else but a station?