the first few stops right out of some interchanges or terminals
consistently gives inaccurate readings. so far amk and bishan
kena.... the bus may switch to arriving out of nowhere but it is
actually still 10 mins away (listed as subsequent)... sometimes
both are listed as arriving or bunching...
2 possibilities conjectured.....
1. nextbus sub-system is not "talking" properly to the nextdep
sub-system at the interchanges. nextdep most likely got its info
from the individual interchanges about the next departure times the
computer assigns to the next bus driver, which means the info is
about a trip that has yet to commence.
however, nextbus uses info based on a trip that has commenced and
tracks it while it is on the road. when bunching occurs on nextbus
for bus stops just after the int/ter (arriving/2mins), it is
probably nextdep giving a timing for nextdep and nextbus using its
own tracking, producing 2 timings, which will be rectified down the
route as nextbus determines the position of the bus (and eliminates
the duplicate).
2. there may be buses that end trips at the interchanges/terminals
but has details of the next trip set. by right DDU/nextdep shld be
smart enough to know how many minutes before the commencement of
the next trip, but nextbus may start indicating 2mins or arriving
on top of timings given to it by nextdep (which is more accurate
here), which may appear as the subsequent bus.
if 2 buses are parking at the interchange, nextbus may start
detecting it as arriving/2mins, arriving/arriving or 2mins/2mins,
which pushes the timing given by nextdep out of projected
timings.
for stops which are somewhere down the route, such issues do not
happen, and it is very very accurate, even displaying bunching like
the bus 64 incident described above.
for example, at the bus stop opposite bishan MRT, svcs 13, 88 and
156 give accurate timings while 52, 54, 55 and 58 keeps having an
unknown "arriving" trip interfereing with the data from time to
time.
will need more investigations, but if SBST will ever want to put up
panels at popular stops for demos and awareness campaigns, Somerset
MRT is a good place where it works well because the profile of the
road before it is pretty straightforward (one straight road) and it
does not have the problem described above associated with stops
close to interchanges and terminals.
another thing is the timing of 174 (town bound) which tends to
early i.e. bus arriving 2-4 mins after the arriving flag is up and
over.
one more observation from bus stop after rifle range rd along
dunearn rd (42059): the evening peak after NP causes buses to be
stuck with Arriving for a few minutes, then it promptly jumps to
the timing of the bus behind as it assumes the bus may have passed
the stop without stopping, before jumping back to Arriving when the
bus has finally arrived 2 to 4 mins after first instance of
Arriving flag. this is alright since it is due to 'external' causes
outside the system's control.
