Everyone knows about services A1 and A2, since they’re pretty much the oldest routes and remained virtually unchanged until 2021. But what of the express services A1E and A2E? Where did they come from?

The express services were actually a fairly recent addition to the ISB network, and their introduction was tied to the opening of Kent Ridge MRT.

Express A1/A2 (2011)

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 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, 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.

A1E and A2E (2013)

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.

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

Revision (2014)

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.


Introduction of Maps (2015)

When NUS prepared the fourth-generation maps, A1E and A2E finally got their own maps. These were the only maps to indicate the stops along the way, using stars.

Interestingly, A1E’s map labelled the stops by name, while A2E’s didn’t.

Presumably, there’s an A2E (AM) map, which doesn’t survive to this day. That would explain the A2E (PM) designation.

Finalisation (2016)

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.

Meanwhile…. don’t ask me why the map of A2E suddenly turned red, with the stop names now labelled.

Fifth Generation Maps (2018)

In 2018, when the fifth-generation maps emerged, OCA made a few cosmetic edits.

A1E was now… not a dotted line.

And A2E is yellow again.

This left us with the express services A1E and A2E, unchanged from 2018 onwards.

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!

COVID-19 Suspension (2020)

Due to the COVID-19 pandemic, students had to be segregated into zones to minimise the chance of cross-infection across different faculties due to NUS’ connected nature. As such, ISB routes were revised and replaced from 20 July 2020 to facilitate zoning, and all existing services were suspended for AY20/21 Semester 1. The service names were not reused.

A1E and A2E, however, were already suspended from 13 April 2020 – there was no official notice on this, but they were not included in the list of services that would operate during the circuit breaker.

Reinstatement (2020)

On 6 December 2020, following the lifting of the zoning policy, the original pre-zoning routes were reinstated. OCA uploaded the route information as follows.

A1E and A2E, however, were not immediately mentioned, leading to questions over whether they will begin operations when the term starts on 11 January 2021. They did begin operations at the start of the term, although the route details never got published on the OCA website.

Withdrawal (2021)

As part of the New ISB Network, Services A1E and A2E were withdrawn from 19 July 2021 onwards. As Services A1E and A2E did not operate during vacation periods, they had already not been in operation for some time. The needs addressed by these services were now addressed by the amended Services A1 and A2, which no longer had layovers at PGP.

Further Reading

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