Why Does Metro Noise Occur?

Although metro systems offer advantages such as speed, convenience, and comfort, and are regarded as one of the representative low-carbon transport modes, urban development often faces constraints such as insufficient road width and excessive road curvature. As a result, newly planned metro lines (like the Taichung MRT and the Circular Line in New Taipei City) are frequently designed under unfavorable conditions, including tight radius curves, sharp bends, steep gradients, small-sized turnouts, and frequent braking. These design constraints give rise to significant noise issues. If not properly addressed, such noise can become a nightmare for residents living along the line. Observing metro systems worldwide, although many countries are aware of the noise problem, concrete and effective solutions are still lacking.

In addition, from an environmental protection perspective, light rail systems generally operate at lower capacities and often run through urban fringe or interface areas. Therefore, “biodegradability” is also a key concern, ensuring that wheel flange lubricants dripping onto the ground do not cause environmental damage. This article shares the advantages of the special wheel flange lubricants developed by Spain’s BRUGAROLAS and their applications in multiple countries, and explores an active noise-reduction solution that balances environmental protection (biodegradability), safety (flame suppression), and economic efficiency (reduced lubricant consumption), providing a reference for metro authorities around the world.

Keywords: noise standards, rolling noise, squeal noise

Active Noise Reduction on Curved Metro Tracks

Based on international experience, active noise-reduction measures mainly focus on wheel flange lubricators. When trains negotiate curves, the wheel flange rubs against the outer rail, generating noise. On-board wheel flange lubrication systems can be used to adjust the friction coefficient at the wheel–rail interface, thereby reducing flange noise. According to experience, these systems are typically installed on the bogies at the ends of the train. Another approach is the use of trackside lubricators. However, whether track lubricators or traditional wheel flange lubricators are used, both approaches present certain drawbacks: