What safety concerns emerged after last year's metro rail bearing pad fall?

A pedestrian was killed today (26 October) after a bearing pad, used to prevent vibration during train operations, came loose and fell near the Farmgate metro rail station, prompting the suspension of metro rail services.

The incident comes approximately 13 months after a similar event on 18 September 2024, when a bearing pad fell from the Dhaka Metro Rail viaduct near the same station, suspending train services between Agargaon and Motijheel for 11 hours.

The 2024 incident had already raised serious safety concerns regarding the design and maintenance of the metro rail system. 

As bearing pad falls, metro rail safety, insurance issues come to fore

Experts at the time attributed the failure to a possible design flaw, noting that the pad fell at a curve where trains exert additional pressure on the structure.

Experts weighed in

Last year, Professor Hadiuzzaman of BUET's Accident Research Institute told Somoy News that the bearing pad came loose at a section where the train makes a turn, which puts more pressure on it. 

He added, "The viaduct was installed without securing the rubber pad to hold the bearings. As a result, the rubber pad could not handle the extra pressure."

He recommended the use of more pressure-resistant, advanced technology pod bearings to prevent such incidents in the future.

In a statement to the Dhaka Tribune last year, Prof Hadiuzzaman explained the function of the bearing pad.

"The bearing pad's job is to compress slightly when a vehicle passes over it and then return to its original position. Since the viaduct has not returned to its original state, it indicates that either the bearing pad has lost its functionality or fallen off."

He added that the viaduct joint where the failure occurred was critical, and that without properly functioning bearing pads, pillars could be at risk. Bearing pads are vital not only for supporting vehicle loads but also for maintaining flexibility during seismic events. Hadiuzzaman emphasized that these bearings must have been rigorously tested before installation, and further investigation was required to determine why the incident occurred.

What are the functions of a bearing pad?

Bearing pads are located at curved sections of the viaduct, where trains exert additional pressure on the structure. Bearing pads in such locations not only support the weight of the train but also absorb lateral forces and vibrations caused by the train changing direction.

The photos show the bearing pad, typically used to prevent vibration during train operations, coming loose and falling at Farmgate, killing a pedestrian. The pad had struck him on the head and as the images capture, it then hit a nearby tea-and-snack shop, shattering its glass front and injuring two others. Photos: TBS/Collected

When a pad fails at a curve, it compromises both load distribution and flexibility, increasing stress on the viaduct pillars and joints. This creates a higher risk of structural damage or collapse, especially during heavy train traffic. 

Additionally, these pads are designed to protect against dynamic forces like vibrations, shocks, and even seismic activity; without them functioning correctly, both the train and people near the track are exposed to serious hazards.

In short, failures in high-pressure, curved sections amplify risks far more than at straight sections of the viaduct.

Systemic issues identified

Investigations into the metro rail system had previously found several systemic problems:

• The design inadequately addressed high-pressure areas, and experts recommended reinforced bearings and more durable metal materials instead of rubber
   
• DMTCL had been operating for nearly two years until 2024 without a mandatory safety certificate from the Dhaka Transport Coordination Authority (DTCA), violating legal requirements
   
• No safety report had been submitted to the DTCA since operations began
   
• No insurance coverage was provided for the metro rail or passengers, nor was there a compensation policy for accidents caused by technical failures
   
• A seven-member probe committee recommended installing cameras to monitor pressure and movement, though it did not conclusively determine a design fault
   
• Authorities had denied claims of a design flaw, stating that various factors could have contributed
   
• DMTCL was working to obtain an independent third-party safety certificate and discussing insurance coverage with Bangladesh Jiban Bima Corporation for future implementation