It’s a longtime joke that the A in A1/A2 stands for Almost Everywhere.

Well, it’s kinda true.

From the inception of ISB services, this service has existed, doing its loop around the Kent Ridge Campus. A1, with a red plastic sign, runs anticlockwise; A2, with a yellow sign, runs clockwise.

Regrettably, A1 and A2 are also the only services most freshmen (and ahem some seniors) know, so they are chronically overcrowded.

An article on just A would be boring beyond imagination because the route of A has barely changed. So I’ll focus more on the express services A1E and A2E. Don’t change the channel!

A1/A2: First Generation Map

The random sentence I threw into my Cinnamon Roll article was actually a terrible joke. “Look beyond the superficialities and you’ll realise the A1 now isn’t the A1 that used to be.”

if you haven’t realised by now, A1 is the service that has experienced the least significant changes throughout its history. A couple of bus stops have been removed or skipped, but other than that the physical route on which the bus travels has not changed a single bit since 2002. A2, on the other hand, has been changed (most notably the removal of TH and EH bus stops) so there is something to be said there.

This was the routing of the A bus in 2002. Look familiar? It’s pretty much the exact same routing as today. Some bus stop names might look unfamiliar, but the routing is the same. Originally, the buses stopped along South Buona Vista Road and near the NUH area.


The first generation map GIF shows… pretty much the same A we know. The A1 route is shown in red, while A2 is shown in barely visible black.

A1/A2: Second Generation Map

Around 2006, with the introduction of Service D, the route maps were revamped. The GIFs were replaced by a series of PDFs which showed the bus routes in a somewhat more user-friendly way. A1 and A2 were now shown clearly on the same map.

This map was more legible, due to the colours used. However, it misleadingly omits the Carpark 13 bus stop from A1 and A2.

The one change to the route that occurred around this time was the removal of the original BIZ2 bus stops; they got merged into today’s BIZ2 stop located under shelter (for A1) and Opp HSSML (for A2).

A1/A2: Third Generation Maps

Following the opening of UTown, around 2011, the maps were revised again to coincide with UTown-related reroutings.

Some time later, the bus stops between Kent Ridge MRT and Science (ie. NUH) were skipped. Website archives are glitchy around that time, but I suspect this was done in 2015 alongside the revision that led to the removal of Temasek Hall and Eusoff Hall bus stops from the A2 route.


So there we have it: the current A1/A2, still crowded as ever.

Express Services

But what of the express services A1E and A2E? Where did they come from?

The express services are actually a fairly new addition to the ISB network, and their introduction is tied to the opening of Kent Ridge MRT.

2011: Express A1/A2

The express services had their roots in 2011. On 10th October of that year, OCA began a new policy whereby during peak hours throughout the day (0930–1000, 1130–1200, 1330–1400, 1430–1600 hrs), service A1/A2 buses would not layover at PGP Terminal but instead continue as a continuous circle service.

This was to encourage students having cross-faculty classes or otherwise to use the PGP pathway to travel between the north and south of Kent Ridge Campus, bypassing Central Forum.

Circa March 2013, this was revised to four peak periods at 9.45am, 11.45am, 1.45pm and 3.45pm.

To differentiate them from normal A1/A2 buses that would layover or “rest” at PGP Terminal, these buses used different signage designating them as Express A1 and Express A2. These routes necessitated a lot of rescheduling to accommodate the lack of a layover along the route.

However, OCA did not record strong passenger loading on the Express A buses around PGP, implying that students were not using the PGP pathway to head to Kent Ridge MRT.

After a few years, due to the difficulty of dispensing with layovers and the difficulty in maintaining schedules, these Express A1 and Express A2 were discontinued.

2013: A1E and A2E

From 5 August 2013, the Express services were stopped, and replaced by the familiar A1E and A2E. Unlike their predecessors, these were true expresses that skipped bus stops along the way.

Based on demand patterns coming out of Kent Ridge MRT (students were already used to using A1 to reach faculties in the morning and A2 to go home in the evening), OCA arranged to have A1E operate in the mornings while A2E operated in the evenings.

a1e a2e

Service A1E (AM) started its route at Kent Ridge MRT, stopping at FoS, CLB, BIZ and then ending at PGP Terminal.

Service A2E (PM) started at Business (Opposite HSSML), stopping at Computer Centre and S17, then serving Opp Kent Ridge MRT before ending at PGP Terminal.

2014: Revision

A2E underwent a significant revision in 2014. In the interest of efficiency, OCA toyed with the idea of getting students to take A2E from Kent Ridge MRT to classes in the morning instead, especially for students at Business who were wasting their time taking the A1/A1E around.

So on 29 September 2014, A2E (AM) was introduced as a trial running during the morning peak hours. This had a slightly different routing from the original A2E (PM), as it started and ended trips at Opp Kent Ridge MRT, and skipped Business and PGP altogether. (At the same time, D2 was extended to Carpark 11 to give MRT-BIZ commuters an alternative to A1.)


On 3 November 2014, the trial was confirmed as a permanent service, and the routings of A2E (AM) and A2E (PM) were aligned. Both would now serve KR MRT, Ventus, Computer Centre and S17, but AM trips started and ended at Opp Kent Ridge MRT while PM trips started and ended at Ventus.


2016: Finalisation

August 2016 (the beginning of AY16/17) saw the finalisation of the express services so far. Due to low ridership, A2E (AM) was discontinued, leaving only PM trips.

At the same time, A1E gained an additional stop opposite UHC. This was to allow it to serve exam crowds heading to the MPSH located behind UHC.

This left us with the express services A1E and A2E exactly as we have them today. As you can see in the map above, A2E is still denoted as PM, a relic of the old days!

While the routings are fixed for regular term time, OCA will sometimes add extra stops during exam periods, such as the A2E temporarily stopping at UHC. Do keep a look out for publicity materials from them or NUSSU!

Further Reading:

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