What the bathtub curve says about MRT Breakdowns | Deep Dive

Key Concepts

• Wear and Tear: The natural degradation of a system or component over time due to use, leading to increased failure rates.
• Bathtub Curve: An engineering concept illustrating the failure rate of a system over its lifespan, characterized by high failure rates at the beginning (infant mortality/teething issues) and end (wear-out phase) of its life, with a lower, constant failure rate in between.
• Teething Issues: Initial problems or malfunctions experienced by a new system, product, or component as it is first put into operation, corresponding to the early failure stage of the bathtub curve.

Singapore's Novel Experience with System Wear and Tear

The discussion highlights Singapore's current situation regarding its public transport infrastructure, particularly the MRT system, as it enters a significant "wear and tear stage." Unlike countries such as Taiwan, which have experienced and learned to "alleviate and perhaps even preempt" such situations multiple times, Singapore is "discovering it for the first time." This novelty contributes to a perceived lack of preparedness for the current challenges.

The Bathtub Curve: An Engineering Framework for System Reliability

A core concept introduced is the Bathtub Curve from engineering. This model posits that any system typically exhibits a higher rate of failure at two distinct points in its lifecycle:

1. Early Life (Infant Mortality/Teething Issues): Immediately after inception, due to manufacturing defects, installation errors, or initial operational adjustments.
2. End of Life (Wear-Out Phase): Towards the end of its expected lifespan, as components degrade and fail due to wear and tear. Between these two phases, the system generally experiences a period of stable, lower failure rates.

Application to Singapore's MRT System

The speaker applies the Bathtub Curve to Singapore's MRT system, noting that different parts of the system are currently at various stages of this curve, which complicates overall reliability from a commuter's perspective.

Thomson-East Coast Line (TEL)

The TEL is identified as being "somewhat at the start of the bathtub curve." This means it is currently experiencing "teething issues" that need to be resolved as it matures into full operation.

Older Lines (North-South and East-West Lines)

For the older North-South and East-West lines, a "major upgrade" was conducted "about a decade or so ago," which successfully addressed many existing issues. However, in the "last year or so," these lines have encountered a "new issue": the introduction of new train sets. While new trains are often perceived as an improvement, they paradoxically reintroduce "teething issues." The process of integrating these new trains and ensuring they "run properly" effectively places this part of the system back into the early, high-failure rate stage of the bathtub curve. The speaker acknowledges that this might sound like "making excuses" but emphasizes it's an inherent challenge in system upgrades.

Challenges with New Train Sets

The introduction of new train sets, despite being "shiny new," necessitates "ironing out a lot of teething issues." This involves ensuring compatibility with existing infrastructure, optimizing performance, and resolving unforeseen operational glitches. The retirement of "very old but still reliable set of trains" and their replacement with new ones means the system is currently in a phase of figuring out the optimal functioning of these new components.

Conclusion and Immediate Objective

The overarching goal is to "get over this early part of the problem" associated with both new lines and new components on older lines, and subsequently "bring down the failure rate." This requires a focused effort to address the current wave of teething issues and wear-and-tear challenges that Singapore's public transport system is experiencing for the first time on this scale.