A wake-up call for safety and reform

In a troubling recurrence for our city's modern transit ambitions, a second incident involving a critical component of the Metro Rail viaduct has occurred, this time with fatal consequences. 

The failure of a "bearing pad", a fundamental structural element,  so early in the system's life raises alarming questions about the construction quality, oversight, and long-term safety management of this vital public infrastructure.

The MRT line in question, which opened in stages starting in December 2022, is a mere two and a half years into operation. For a bearing pad, designed with a lifespan of 20-30 years, to fail so catastrophically is not a matter of ageing; it is a clear signal of deeper, more fundamental problems.

The critical component and its failure

Bearing pads are the unsung heroes of any elevated rail or road network. Made of an elastomeric rubber-steel composite, they sit between the concrete deck (the bridge that carries the trains) and the supporting piers. 

Their primary roles are to evenly distribute the immense weight of passing trains, absorb vibrations, and accommodate natural movements caused by temperature changes and traffic. 

When they fail—through hardening, extrusion, misalignment, or, as in this case, a complete dislocation or "fall down"—the results are catastrophic. The load distribution becomes uneven, creating dangerous stress concentrations that can misalign the deck and damage the piers themselves.

Probable causes: A litany of concerns

Given the system's infancy, the probable causes narrow down significantly. Premature degradation or lack of maintenance is highly unlikely at this stage. The evidence strongly points towards two interconnected areas:

1. Design flaws or installation errors: This is the most probable culprit. Incorrect levelling of the pier surface, uneven thickness of the pads, improper installation, or insufficient lateral confinement during construction can all lead to a premature failure. The bearing was not functioning as intended from the very beginning.
2. Insufficient supervision during construction: There was a serious shortage of experienced technical manpower. The Project Implementation Unit (PIU) was weak, staffed mostly by a few deputed engineers from RHD and Railways. The then Managing Director reportedly resisted recruiting technical personnel, relying heavily on consultants while being led by non-technical administrators.  

The fact that this is the second such incident within a year confirms that the root cause of the initial failure was never properly identified and rectified. This recurrence is a damning indictment of the current safety audit and accountability processes.

Workers involved in the construction phase, many with experience in the Middle East and Singapore, accustomed to strict compliance standards, reportedly raised concerns about poor safety practices and lack of oversight. Some even complained directly, saying work was continuing without proper supervision or adherence to safety protocols.

Safety measures and recommendations

The fact that this is the second such incident within a year confirms that the root cause of the initial failure was never properly identified and rectified. This recurrence is a damning indictment of the current safety audit and accountability processes.

The current metro system is not even operating at full designed capacity. As service intensity increases, so will the stress on these vulnerable components. Photo: Rajib Dhar

A system at risk and the path forward

It is worth noting that the current metro system is not even operating at its full designed capacity, with longer headways and fewer compartments. As service intensity increases, so will the dynamic loads and vibrations, placing even greater stress on these vulnerable components.

To prevent a third, potentially more disastrous incident, a fundamental shift in approach is required. The following steps are recommended. 

1. An independent, expert-led safety audit: A thorough investigation by a truly independent and technically competent body must be commissioned immediately to find the root cause. This cannot be an internal exercise.
2. Immediate structural mitigation: For all critical viaduct sections, the authority must inspect and, if necessary, install additional lateral restraints like shear keys or guide bars to prevent displacement.
3. Establish a technically empowered maintenance unit: DMTCL must establish a strong, in-house maintenance unit staffed by qualified engineers, not bureaucrats, with the authority and expertise to enforce rigorous inspection schedules, including six-monthly visual checks and annual load testing.
4. Structural reform of DMTCL: The agency managing this multi-billion-dollar infrastructure must be a knowledge-based, service-oriented organisation led by technically qualified professionals. The current dominance of deputed or retired bureaucrats in key technical and decision-making roles is a significant risk to operational safety. 

In short, these successive incidents have sown a seed of fear among the public, eroding confidence not just among metro users but also for the thousands who commute on the roads beneath the viaduct daily. If we fail to pinpoint the root cause, hold the responsible parties accountable, and implement serious structural reforms, we will be inviting further disaster. The safety of millions depends on transforming the DMTCL into a competent, technical institution capable of stewarding our city's transit future. This fatal incident must be the catalyst for that change.

Md Shamsul Hoque is former director, DMTCL, and director, Accident Research Institute, Buet.