Bus arrival time system: How does it work, and when was it introduced?

SINGAPORE – Since 8pm on Jan 21, public transport users in Singapore have been unable to check when their buses will arrive.

The expected time of arrival system that is used to communicate bus timings

underwent a reset

on the evening of Jan 21, after being affected by a technical issue that resulted in wrong timings, as well as long waiting times, being displayed across various channels.

The issue was first detected by the Land Transport Authority (LTA) on Jan 10, and announced to the public on Jan 21.

The authority said it had detected more inaccuracies over the course of the week after the first discovery.

In an update on Jan 22, the LTA said its engineers and system contractor found a memory cache build-up in the on-board systems of some buses.

This disrupted data transmissions between buses and the central servers that compute the estimated arrival times. About half of the bus fleet – across operators – has been affected.

It said it will take

another four days

for the issue to be completely fixed, as it works with the contractor to reconfigure the system and clear the cache on affected buses.

Q: How does it work?

A: The expected time of arrival system informs commuters when their buses will arrive, making use of millions of data points.

In 2015, when the LTA introduced its centralised system, it said it collected

more than 50 million data points

every day from the 4,700 public buses that were operating at the time. As at the end of 2024, there were 5,841 public buses in Singapore.

After global positioning devices on buses send location data to the authority, the system then predicts arrival timings based on real-time bus locations, route information, bus timetables and historical travel times.

The LTA said in 2015 that 95 per cent of estimated timings fall within three minutes of actual arrival times.

Achieving an accuracy level of 100 per cent was not possible, said the authority’s group director for innovation and infocomm technology then, citing the unpredictable nature of traffic, such as accidents.

The estimated arrival times are then put up on bus stop displays and mobile applications, including the LTA’s MyTransport.SG app and third-party apps such as SG BusLeh, which has more than one million downloads through the Google Play Store.

Q: When was it introduced?

A: The idea of communicating bus arrival information to the public was first mooted in a White Paper published by the LTA in 1996.

In the paper titled A World Class Land Transport System, the authority said this “will consciously reduce the burden and anxiety of waiting for buses”.

Two selected bus stops in Orchard Boulevard displayed bus arrival times as part of a pilot project, and the LTA said it would expand the project over the next two years.

Eventually, it planned to have bus arrival information accessible from commuters’ homes, whether through the now-defunct video-text system Teleview, the internet or telephone hotlines. “Commuters can then make better use of their time at bus stops, MRT stations or at home,” the LTA said at the time.

Bus arrival information panels were launched in 2007 by the LTA, pulling information provided by SBS Transit and SMRT. These panels were put up at 30 bus stops in the Central Business District, as well as in Yishun and Ang Mo Kio.

SBS Transit also released its own Intelligent Route Information System, or Iris, that year. Both served similar purposes, informing the public about bus arrival times.

The two platforms were said to be accurate within allowances of up to three minutes, although past news reports showed that the public saw room for improvement in terms of accuracy.

In 2009, the LTA tweaked its system so it could predict traffic flow, with the aim of improving accuracy. It then launched its own system in April 2015. The information was put up on the authority’s MyTransport.SG app, as well as third-party applications.

Q: What about third-party applications?

A: Every third-party application that provides bus timings in Singapore draws information from the LTA.

The authority has a platform called DataMall, on which it publishes real-time and historical transport data, including bus arrival timings.

With the system being reset, third-party applications have been unable to provide real-time estimates.

In Google Maps’ case, checks by The Straits Times showed that it was still providing bus interval information.

While it can gauge how long a journey would take by bus, it cannot inform passengers when buses would get to them.