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.

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, at that point A1 was 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 had not changed a single bit since 2002. A2, on the other hand, had 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 in 2019. 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.

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).

Third Generation Maps

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

Fourth Generation Maps

Some time later, the bus stops between Kent Ridge MRT and Science (ie. NUH) were skipped, and the ending of the route was changed from PGP to the driveway of PGP Residences.

Website archives are glitchy around that time, but I suspect this was done in 2015 alongside the 1 August 2015 revision that led to the removal of Temasek Hall and Eusoff Hall bus stops from the A2 route.

With these changes, NUS redesigned their maps, forming a fourth generation. Here, A1 and A2 each got their own map.

Fifth Generation Maps

In 2018, when OCA shifted to the UCI website, the maps were briefly lost. NUSSU pretty much asked where they had gone, so OCA dug them out and added the stops into the maps to form the current fifth generation.

So there we had it: A1/A2, still crowded as ever. PGP House 7 was somewhat removed as a stop in 2018, so this map reflects that.

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.

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.

There was one change to service A2: according to the official stop listing, the House 12 stop along Prince George’s Park (which service CC passed by without stopping) was removed. This was because during the zoned semester, the stop itself was demolished as House 12 was reconstructed as the SNRSI building. The route map image, however, was not updated and continued to show that stop (typoed as “PGP 15”).

Major Amendment (2021)

Summer 2021 saw great changes to Services A1 and A2. They underwent a significant amendment in the New ISB Network that took effect from 19 July 2021. The operating details of the amended routes were announced on 14 June 2021.

The A services largely maintained their direction and roles as trunk services connecting the entire Kent Ridge Campus. However, the layover point for the services was shifted from Prince George’s Park to Kent Ridge Bus Terminal, between CLB and LT 13 (for A1) and Ventus and IT (for A2). As a result, Service A1 and A2 no longer directly connected CLB/IT with LT 13/Ventus, a connection that was maintained by Service D1.

The following images are updated July 2022.

The amendment was done to better connect passengers via PGP, a currently underutilised sector of the route. Previously, passengers heading between KR MRT and the southern areas of the Kent Ridge Campus (SoC and BIZ) would not typically travel via PGP as they would need to transfer at PGP. Instead, they would travel around the rest of the campus, technically making a longer journey but without needing to transfer. This was exacerbated by the fact that Service A2 ended at PGPR while starting at PGP, meaning that passengers transferring from A2 to A2 needed to walk about five minutes.

Now that the layovers of A1 and A2 have been shifted to Kent Ridge Bus Terminal, the services do not layover at PGP, thus enabling students to travel via PGP without transferring buses. I foresee that this will have a great impact on reducing crowding in the mornings. Passengers heading as far as CLB can continue to wait for A1 at the KR MRT bus stop, while those heading to FASS, SoC and BIZ will cross the underpass to Opp KR MRT to wait for A2. Thus, the passenger loading will be balanced between the two buses and the two bus stops.

The same will occur in the evening peaks, in the reverse direction. There is also a secondary benefit here: as LT13 and IT will now be the second bus stops of A1 and A2 respectively, the ISB system will have better capacity to carry the large crowds at these nodes off to Kent Ridge MRT.

Sixth Generation Maps

A new sixth-generation route map was introduced for Services A1 and A2, featuring the routes overlaid on a black-and-white map of the Kent Ridge Campus for better visibility.

Further Reading:

All Episodes

19 thoughts on “History of Bus Routes Ep 4: A1/A2

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