Fate of the Bukit Panjang LRT

As the fault-ridden Bukit Panjang LRT (BPLRT) that connects the satellite towns of Choa Chu Kang and Bukit Panjang reaches the end of its 20-year lifespan, SMRT and the Land Transport Authority (LTA) have announced options dealing with the fate of the LRT line after 2019 (The line opened in 1999). These options are the following:

  1. Replacing the current Bombardier Innovia APM system with self-powered autonomous guided vehicles on the existing viaducts.
  2. Building a new conventional LRT system with significant design enhancements in key infrastructures such as power supply, signalling, rolling stock, tracks and stations.
  3. Renewing the current Bombardier system with a communications-based train control system (CBTC).
  4. Completely scrapping the LRT in favour of conventional public buses.

So what are the pros and cons of these options and which of them is the best option? Let’s discuss each option and its implications.

1. Self-powered autonomous guided vehicles


One of the biggest problems confronting the BPLRT were power faults, which was partially a result of the design of the Adtranz C-100 (The predecessor to the Bombardier Innovia APM 100) design, where the train relies the guidance, signalling and communications and power on the centre guide rail:

How the Adtranz C-100 rubber-tyred APM system works. Notice that the centre rail provides the guidance, current and signalling communication to the train. Diagram courtesy of Straits Times.

Hence, with the issue that ‘putting all their eggs (the important aspects of operation of the train) into one basket (the centre guide rail)’ being a key issue the BPLRT was facing, the proposal suggested self-powered vehicles to allow for the power source of the LRT to be isolated from other crucial aspects of the system such as the signalling and safety systems.

What it could mean:

The means of powering the LRT trains would be converted from using a live rail to provide current for the train to their own power source, which could range from diesel to rechargeable cells. This would mean that the LRT trains would have to be converted to a diesel multiple unit (DMU) or a battery-electric multiple unit (BEMU). However, what are these types of trains?

A multiple unit is a type of train which consists of several self-propelled passenger or freight units coupled together that are powered by various means, ranging from diesel traction for DMUs to drawing electric current from an electrified third rail or overhead wires for electric multiple units (EMU). For a DMU, it is directly powered by diesel that is carried on board and is combusted in the underfloor equipment to produce electricity to drive the train and provide auxiliary power while for a BEMU, it is a rechargeable cell that provides the electricity instead of external sources.


In the case of the Bukit Panjang LRT, the benefit is that the isolation of the power source from the signalling and communications could lighten the burden on the centre rail and hence make it less likely to have disruptions. However, there are also significant downsides:

  • If the LRT trains are converted to run on diesel instead, it could be less environmentally-friendly as diesel fumes could be produced in the process and it would not be healthy for residents living along the LRT line.
  • Even if the trains are cell-powered, the customization of the system to accommodate an external power source would could incur unnecessary costs.

Ultimately, this option is good in the short run by addressing the problems of relying everything on the centre guide rail but not sustainable in the long run as the system is in need of a complete overhaul to a more reliable system.

Likelihood: 7/10

2. New LRT system with enhanced key infrastructure.


As the town estates, including Punggol, mature over time, the newer LRT lines such as those in Sengkang and Punggol are reaching their maximum capacity even though they were adequately designed for the long term plans for the corresponding estate. This can be seen with the evolution of the platform widths of the LRT stations at the town centres:

Choa Chu Kang LRT platforms are the narrowest and the shortest among the major LRT stations in the town centres, with each platform at 39 metres long, just enough for 3 LRT cars and about 7 metres wide. This makes it of the same length as the other non-interchange stations along the Bukit Panjang LRT network, causing chronic congestion in the station that eventually prompted the addition of two additional side platforms for alighting only. Photo courtesy of Land Transport Guru.
Sengkang LRT station is also rather narrow, with only a width of 10 metres, just slightly wider than the platforms at Choa Chu Kang. However, it is notably longer at 47 metres long (approximately 4 LRT trains), allowing for more space for alighting, boarding and transfer to the MRT station below. The two ends of the platform also feature more space for trains to stop at, spanning the full length of the MRT station itself. Photo courtesy of Land Transport Guru.
At 67 metres long, Punggol station has the longest LRT platforms – long enough for more than 5 LRT trains and just 3 metres shy of accommodating a full 3-car MRT train – and is even wider at a width of about 24 metres. The two ends of the platform are even longer than that of Sengkang’s, with the whole station structure spanning 300 metres long. While this was intended for a middle track provision for a possible Punggol North spur line, LTA appears to have shelved this plan and replaced it with an extension of the North East Line, acknowledging that perhaps LRT alone is insufficient to serve future developments. Photo courtesy of Land Transport Guru.

Even with the evolution of the platform design of the LRT station serving the town centre and the introduction of two-car operations on the more recent LRT lines, this is becoming inadequate for the LRT systems as they reach their maximum capacity. Also, the government has been in favour of building MRT lines instead of LRT lines to serve whole estates as seen in how a proposed Jurong Region LRT line eventually evolved to a fully-fledged MRT line in planning on transportation for Jurong.

Also noteworthy is that the Sengkang and Punggol LRT lines (SPLRT) were greenfield applications where they were built along with the estate (Sengkang) or before the estate was developed (Punggol) but even the capacity of these lines are now inadequate for the estates. Now consider the brownfield application of the Bukit Panjang LRT into two already built-up estates.

In light of this, this gives a possibility that the Bukit Panjang LRT would have to be upgraded to a medium-capacity transit system similar to systems such as the Taipei MRT Brown Line and the rapidKL Kelana Jaya Line. This is because despite the now inadequate infrastructure of the BPLRT to serve Choa Chu Kang and Bukit Panjang the corridor is not large enough for a heavy capacity MRT line.

What it could mean:

If option 2 comes to fruition, the LRT would have to close in stages, preferably first the loop and Ten Mile Junction and then the route between Choa Chu Kang to Phoenix, to lengthen the platform and improve the station facilities and replace the guideway system and rolling stock. During this time, a bus rapid transit (BRT) system (a bus system that utilises high capacity zero-step buses and mostly segregated lanes) would also have to be implemented within Bukit Panjang and between Bukit Panjang and Choa Chu Kang as an interim measure. Upon the completion of each stage, the BRT system would then remain in place as a means to ‘feed’ into the improved LRT line and as a bridging service if the LRT system fails again.

Technology-wise, the Bombardier Innovia APM system would have to be replaced with a more reliable system such as the Japan-developed New Transport System (the basis for the more reliable Mitsubishi Crystal Mover used in SPLRT) used for the Yurikamome in Tokyo Waterfront and the Port Liner in Kobe.


This would be best option in the long run as not only it gives the BPLRT a long-deserved upgrade in its reliability, it also helps to improve the connectivity of the system as a new BRT system that duplicates the capacity, hence relieving congestion on the LRT and provides a fail-safe operation. While there is legitimate concerns that some upgrades such as the new LRT trains would be ‘wasted’, these ‘wasted’ trains can also be exported second-hand to other similar systems such as the Miami Metromover. Singapore also has sufficient experience of such upgrades like the upgrading of the Changi Airport Skytrain in 2006 from an Adtranz C-100 system to a Mitsubishi Crystal Mover in anticipation for Terminal 3.

Likelihood: 7.5/10

3. Upgrading the existing system.


Similar to the argument for option 1, the system used has several key flaws such as in the signalling system, which saw an antenna fault causing a train to skip three stations. Under such context, SMRT is currently looking into upgrading the current fixed-block Cityflo 550 Automatic Train Control (ATC) system to a CBTC system.

What it could mean:

In a fixed-block signalling system, the line is separated into separate blocks which only one train can occupy. The track circuits help to determine which block is occupied by shunts (short circuit due to the presence of a train that causes a red signal) and hence provide the appropriate signals to the train as to whether to go or stop and the speed limit to adhere to:

Speed Signalled Fixed Block
Fixed block signalling system. Each block is the space between the the signals. The braking curve is calculated by the number of blocks between the two trains. Diagram courtesy of SGTrains.

In a moving block signalling system, the trains are the blocks and the braking curve is calculated based on the distance from the train ahead by the on-board computer systems:

Moving Block
Moving block signalling system. The trains are the blocks and the trains brake based on the distance between the trains. Diagram courtesy of SGTrains.

Under such circumstances, this would allow trains to be closer together and allow for shorter headways, which is defined as the minimum time between two consecutive vehicles. Hence one could anticipate for shorter waiting times if option 3 is chosen.


This option is viable as the upgrade allows for shorter waiting times and would also apply redundancies that serve as back up if the main system fails. Also, like the case of the re-signalling of the NSEWL, inconveniences can be averted as such work can be done at night. However, as it retains the current AC power supply, the shortcomings of the current electrification could (but not necessarily) hinder the improvements from the signalling upgrade.

Likelihood: 7.5/10

4. Scrapping the LRT system

Context and what it could mean:

In an blog by SMRT, SMRT hinted that given the age and unreliability of the system used (BPLRT is one of the two non-airport applications of the Bombardier Innovia APM, the other being in Miami), it could well scrap the system and replace it with more bus routes. Noted in this blog is that “a fully loaded high-capacity bus like a double-decker can take 130 passengers, which is more than the 105-person capacity of a single Bombardier train”, hence noting that a benefit of this would be increased capacity.


This option is not feasible in the long run and is also very unlikely going to happen. Even in the same blog, SMRT noted that a problem would be ‘increased road congestion’, nullifying the positive effects of scrapping the LRT system. Also, netizens have also lashed out at this option as a poor decision. Even Transport Minister Mr Khaw Boon Wan indicated that such an option is ‘unfeasible’ as “the road network in Bukit Panjang will not be able to cope with the increased congestion”. Instead, he recommended that “many key components of the LRT, including the trains, power rail and the signalling system, have to be replaced in about four to five years’ time as they would be out of date.”

Likelihood: 2/10

To wrap up:

Ultimately, comparing the four options, the best would be the second option as it would give the BPLRT a complete overhaul to become a much more reliable system, be more able to cope with passenger usage of the line, and provide a fallback measure (the BRT system). Even though this would inconvenience passengers, these short-term inconveniences are offset by the stated interim measures. The third option would be next best option as it helps shorten waiting times while the first option is third because the best it does is to improve the power supply system.


Author: sbs9834c

A transport enthusiast and SRJC alumnus who has served an internship with the LTA and is awaiting for university matriculation into SUTD.

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