I had the same question. So I have actually monitored all JIS
services during peak hours. Each bus takes 80-120 pax between 06.45
and 08.15am in morning peak. Other way round buses come totally
empty. I am not sure if the buses should run uni-directional during
this time slot - at least services 249, 251. For 182,192, 193, 252,
254, 255, 257 they have other loading points at Joo Koon, Tuas
in opposite direction though that loading is far less worthy of
DDs.
Evening peak, the loading gets distributed. I counted for 246,
249, 251, 252 the number of pax alighting at Boon Lay Interchange
(easier to do than for 182, 254). The number of pax varied between
50 - 70 pax for 246, 251. For 249 and 252 was more for certain
buses but far lesser than AM peak as the peak hour in PM is more
spread out.
I also feel the frequency of certain JIS services like 249, 252
needs improvement and one BSEP bus should be added each.
It's funny how BSEP on 246 seems to mean just adding one Wright
(SBS3325U) and that's it. They should make some of thse buses SD
and have more buses than just six. Not sure for the other JIS
services, but since 246 also serves some neighbourhoods like
mine...