Appears that you all have only the answer 189 in mind...
actually, it's 169!
Hint 1: Boarded a bus of a company where there are majority of
buses are from the same company.
Woodlands Reg Int.
SMRT: 169, 178, 187, 856, 858, 900, 901, 903, 911, 912, 913, 925,
926, 960, 961, 962, 963, 964, 965, 966, 969
SBST: 161, 168
Hint 2: Will meet 4 other bus services from the boarding stop for 2
stops at least.
856, 858, 965,
969
Hint 3: I like to see interchanges & terminals along the
route.
Yishun Int, Admiralty Rd West
Ter
Hint 4: The bus I took used to be under another company.
169 - Taken over in
1983!
Hint 5: Most people on this bus during evenings are indians.
169 @ Admiralty Rd
West
Hint 6: If I add up the digits of the bus svc I take, it will be
the same number as the first number(s) of this bus svc.
1+6+9=16 9
Hint 7: I take this bus eastwards.
Towards Yishun from
Woodlands.
Hint 8: Alighting stop is near a park.
Yishun Town
Park
Hint 9: The bus company of the svc I took has majority of buses at
this stop also.
SMRT 811, 851, 852, 853, 854, 855, 857, 858, 965, 969
SBST: 39
Hint 10: No JCs seen along the route.
Add on: Along my route. 169 only
passes YJC after my stop.
Adding on...
Hint 11: As mentioned in hint 2, 3 of the services ply on
expressways (Includes Jln Toa Payoh).
858, 965,
969
Hint 12: As mentioned in hint 2, 2 services are of same series as
each other. Same for the other 2.
856, 858 = 85x series
965, 969 = 96x series
Hint 13: Where to get rubber?
Someone related. Linked to hint
18.
Hint 14: Lots of trees.
More trees = More wood. Wood on
land = Woodlands 
Hint 15: Take this bus can go 2 libraries.
WRL, AMCL
5 More clues:
Hint 16: Journey takes half of the time of the whole route.
30 minutes. 60 minutes complete
all.
Hint 17: Both ends of this route are interchanges
AMK Int and WDL
Int
Hint 18: Ah Lim at alighting stop =)
Lim Nee Soon's statue at Yishun
Town Park
Hint 19: Boarding stop is unique.
Woodlands Regional Int
(underground)
Hint 20: The bus svc I took had been through a merger.
169 merged with 857 in
1996.
Trip I took: 169 from WDL Int to
Yishun Town Pk.
Got it?