They trying max out the no. of trips for the 518 DD, I supposed.
It needs to reach back in time to start its last trip (or downrun).
IIRC, it is either the third or second last bus to reach Pasir Ris
Int (seen it at 12.40am while last bus to reach Loyang is normally
1am)
S-shift DDs are helpful as driver do not need to waste time to
tell passengers to move in.
321 formally use LOs before (according to old forum posts) but
that is a 2x DD. Not sure about 3x DDs plying Hougang St 11
Hmm, that's interesting with the late-night timings for 3818P.
If that's the case, then 3818P easily runs the most hours on Sv 518
compared to the other buses uh..
But idk, in my opinion, it would make a big difference if they
shifted 3818P to one slot later than what it's usually doing now.
Considering one slot is 15mins average apart, it would easily mean
that it reaches Orchard-Suntec during PM Peak right where the most
people would queue to take Sv 518. And more justification to the
SBST people in answering whether they should deploy more DDs for Sv
518 in the future.