When I asked, they said one of the reasons is because of traffic
conditions. By the time they get to NTU to start trip after
negotiating all the traffic lights, they may be up to 5min late.
But some other BCs would be 1 or 2min early and don't want to wait,
so just strat trip. So, in the end 4 or 5 start bus together!

But now, this won't happen as often. A new timetable is effective
this week.
In the past, in the late PM peak (18.30 onwards), 12 out of 19
buses would be on 179A, the other 4 on 242.
Now, in the latest revision, only 7 out of the 19 buses are on 179A
in late PM peak.
For PM peak now, BCs either do all 179 trips, or do 1 179 trip
before x-overing to 179A, or do all 179A trips. No more messy
x-overing from 179 to 179A then back to 179, etc... 