In this case the bus company has paid for the traffic lights to be
installed. The traffic light controller knows perfectly well when a
bus has arrived. The traffic light engineer simply refuses to program
the lights correctly.
Let's say that there is supposed to be a bus exactly every 10 minutes,
and the trip actually takes nearly 10 minutes. An extra 10 or 20
seconds of wasted time on each trip can make the buses late all day.

I think I would have to suggest that, given all the variables that might
impede a bus's journey - old ladies with walking sticks and shopping bags
trying to clamber on, mothers with kids and push chairs, local authority /
gas board / water board etc digging up the road, weather conditions, people
with no change and so on - if a ten second delay at a set of lights could
screw up the timetable for the day, then the person that determined the
scheduling, got it wrong ...

Arfa