Hi everyone!
Flagging for the bus is generally required (and best to do so to
avoid missing the bus 
)
However, there are now increasing numbers of bus captains / service
captains who would take the initiative to slow down the bus and
give a horn before reaching the bus stops to alert people at the
bus stop of the buses' arrival, which i must say is a good
thing.
This is especially noticeable in industrial estates where the
waiting time for buses is slightly longer.
I have noticed some people at bus stops in deep thought who are
brought back to the present by the horns.
Sometimes, bus captains / service captains would also note familiar
/ regular passengers on their routes. For example, i remembered
once on my way to sch i dozed off. When i awoke, the bus was
driving into the bus bay of my usual transfer stop even when i
forgot the press the bell. (there was no one waiting for the bus at
the bus stop) Had he not bothered to do so i would have missed the
stop. Heehee.
A possible reason for buses to sometimes drive into the bus stop
bay and stay there for a while even if no one is at the bus stop
might be because the bus is slightly ahead of schedule. (I have
noticed bus captains doing so and checking the fare machine.)
Afterall, schedule of buses might not be as easily regulated as
trains, perhaps due to traffic conditions and the fact that they do
not have a really dedicated path to travel on (bus lanes are
somewhat so but other vehicles still do share the lane
sometimes).
Anyway, these are just my 2 cents' comment on this issue, as a
fellow bus commuter.
On a lighter note, i have been reminded by my sis that there is no
need to flag down the bus at the interchange, which i did when i
was at the start of the queue. LOL! Guess some habits die hard
heehee.
Regards,
Ebenezer