As part of campus zoning measures to handle the COVID-19 pandemic, ISB routes were organised by zones. The AA services, introduced on 20 July 2020, served Zone A, which includes Engineering, YSTCM, SDE, Yale-NUS College, UTown, SCALE, USP, YIH, TLab and SNRSI. Only students whose zone is Zone A (including RC residents in UTown) were allowed to board AA buses.

The AA buses are not to be confused with A1 and A2. They do not ply the entire campus, and only go around Zone A.

OCA uploaded the following summary graphic for route AA on their website.

AA1 and AA2 connected the hubs of PGP, Kent Ridge MRT and UTown to destinations in Zone A; they also stopped at University Health Centre.

The difference between the two services is the direction in which they traverse Zone A. AA1 buses travelled clockwise via YIH, Central Library, Kent Vale, Museum and then UTown, while AA2 buses travelled anticlockwise via UTown first, then Raffles Hall, Kent Vale, EA and NUS IT.

This means that from Kent Ridge MRT to UTown, the most direct route was AA2; from UTown to Kent Ridge MRT, the most direct route was AA1.

Note that AA2 did not stop at Opp YIH.

The doubled letters AA are used to avoid confusion with the previous A services, which circumnavigated the Kent Ridge campus. Tentatively, both routes have been coloured green, based on the Zone A colour.


Buses permanently deployed to AA1 and AA2 during AY20/21 Semester 1 included:

  • PC3763G
  • PC3769R
  • PC3849T
  • PC3954Y
  • PC3967K
  • PC3972U
  • PC3989Y
  • PC4009U
  • PC4038K
  • PC4051X


Following the lifting of NUS’ zoning policy on 6 December 2020, these and other zoned routes were withdrawn and replaced by the original, pre-zoning routes on the same day.


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