Let’s talk about the Bukit Panjang LRT
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Can we fix it? Should we fix it? How can we fix it?
Editor’s note: This is a guest article written by Ren Jie, a close friend of mine who’s also rather well-informed on matters. Ren Jie approached me to write an article about the BPLRT, and I thought, why not? Another perspective besides mine would be a welcome change of pace. As again, do feel free to question and comment below.
Usual disclaimer: The views expressed in this article are solely his, and do not represent the views of me, the FTRL blog, or any of the stakeholders in the rail network. Just getting this out of the way, and I hope you’ll enjoy this piece!
~Yuka
Always being in the spotlight for the wrong reasons, breakdowns along the Bukit Panjang LRT (BPLRT) is commonplace and not a surprise to many Singaporeans. It was a pioneering project in Singapore, and is the only LRT line in Singapore to be built in a developed HDB estate at that point in time.
The many design problems it is plagued with, is attributed to its steep gradients, of which the LRT tends to stall due to insufficient power or contact with the powered rail, or vulnerable crossovers, that causes much of delays attributed to rapid wear and tear.
This article will cover two , first being what may have caused the current spate of disruptions and second, what are my opinions on the technologies that can be used in the renewing of the BPLRT network.
Let’s go straight to the point. The most recent six hour breakdown on 9 September 2017. What caused it? What is this grief that commuters have with the system?
The damaged segment of rail was just outside Ten Mile Junction station, causing two trains to stall while returning to the depot. This might pique the curiousity of many, considering mainline or Sengkang Punggol LRT trains do not cause such an issue, so why is this occurring? While there are many reasons that I have theorized, let’s find out.
Broken Metal Brackets: Wear and Fatigue
The metal brackets (referring to those holding the power/signal ‘tracks’ in this section) are extremely vulnerable due to its solid thin bracket design (possibly close to 20mm thick). The solid nature of the bracket as compared to hollow core ones for the third rail on the North-South East-West Lines (NSEWL) may increase the chance of damage through torsion or bending, triggered by the vibrations through the beam guideway (of which vibrations are caused by the train passing by).
Crossover segments or segments with tight turning radius are especially susceptible to this type of damage due to the turning required, causing torsion on the brackets as the power and signal collectors touch on the rails. As insufficient time is provided for the brackets to ‘heal’, the brackets experience what we call, metal fatigue from wear and slowly, breaks or dislocates, which is what I believe to have cause trains to stall during the current breakdown incident.
The system was not designed for such a high frequency and complex switching of tracks with the track design, even not for the increase in trains bought (the C801As) to further increase the frequency of the BPLRT, further causing increased wear and tear in the network, with the same amount of maintenance and equipment used as before.
Increased Vibrations: Beam Guideway Supports
Two types of supports are being used here, firstly, a standard metal bracket to prop the beam guideway system. Secondly, concrete sleepers (similar to other Automated People Mover systems overseas) to support segments of the guideway near, before or after crossover track sections.
The movement of trains would cause vibrations onto the beam guideway system. Due to the design of the metal brackets (in this section and on, referring to the ones under the beam guideway), for majority of the network, that were used to prop up the beam guideway system, the vibrations cannot be transferred to the ballasts or to the viaducts easily as compared to mainline trains. Hence, vibrations are spread out lengthwise further and down through the metal props instead of vertically down. This is worsened by increasing the amount of trains on the network, which increased the rate of wear of the components.
Crossover track sections are extremely vulnerable as the track piece is being held by a track switch mechanism instead of a concrete sleeper. Without the long length of guideway for the vibrations to spread out and spread vertically downwards to the viaducts, the supporting mechanisms in the track switch holding the track piece would be worn faster, as more vibrations is being transferred through a shorter surface area.
This caused the ultimate situation, as the train moves, it exerts torsion in a direction on the guideway, causing pressure on the metal brackets. An excessive amount caused the ‘sheared brackets’, which is the cause of the breakdown.
Design Flaw: Steep Gradients and Curves
Although not directly related to this breakdown incident, it has been related to many others. One can be that the Innovia APM 100 is not built for conquering such gradients and that it is generally built for use in Airports. Hence, upon reaching a large incline, the LRT unit will begin to stall.
As the Innovia APM 100 system is guided along the viaduct with its central beam guideway, tight curves or gradients may increase the wear and tear of the Current Collector Device (CCD). This may lead to the power/ground rail to be damaged by a damaged CCD as it might exert unnecessary pressure onto the rails, which may dislodge it over time.
Despite the challenges faced and design numerous issues/mistakes, there could be ways to improve and upgrade the current network system, for instance, SMRT is ‘replacing rail brackets with fortified design at critical segments’. (Assuming this work is to remedy the shear force on the metal brackets at tight and crossover tracks)
The Solutions
Well, let’s come to the gist of this upgrading that SMRT Trains CEO, Mr Lee Ling Wee has talked about slightly less than a year ago and what has been debated at the parliament earlier on this year.
Mr Lee offered 4 options (fourth not labelled), the first, being an autonomous vehicle running on its own power and the last, removing the entire network, being rejected by the authorities. The Straits Times did not cover on the reasons on why the authorities rejected the first, but I do agree that the last option would simply not work out, since the town has grew much reliance on the network, with the Downtown Line feeding in at Bukit Panjang LRT station.
Autonomous vehicles: Why I personally think it is a good idea
Why I think that autonomous vehicles is a good and faster solution to implement, while making full use of the current new C801As that we have just procured. A smart electric battery that has enough battery with excess, to run from the furthest point of BPLRT back to the depot, in case of battery failure. These electric vehicles would either, one, run as its primary means of power, two, runs with a diesel generator as a backup source of power.
For point 1, these vehicles would be able to charge up at stations into its battery installed on the trains. Batteries should last at the very minimum, a full Service A/B trip and a smart detection system installed in the event of battery charging failure, the affected train will be removed from service at the earliest possible timing. This will allow the ground and power rails to be removed, solving bulk of the cause of disruptions.
For point 2, a diesel backup could be installed in the event of power loss, whether with a train battery fault or systemwide power failure. This ensures that the LRT system can continue to run when an isolated or systemwide fault occurs while engineers find a solution to the problem, ensuring an increased uptime and greater reliability
Other technologies that could be integrated with point 2 is using GPS, LIDAR (Light Detection and Ranging) technology and transponders to pinpoint the location of the vehicles, obstructions in way (like human, furniture that has been on the network) and relay to the operation control center. This may be possible, considering SMRT acquired a stake in driverless company 2getthere which offers such a solution. Paired with a larger version of their Group Rapid Transit (GRT) vehicles, this might be the solution that we are looking for.
This rejuvenation project for BPLRT is a great opportunity to showcase and make things work, with next generation cutting-edge technologies. Let’s make a project done wrong, into a project done right, after 20 years.
