What is the most probable reason for limiting train speeds in under-river tunnels?

Limiting train speeds in under-river tunnels is primarily associated with the need for ensuring passenger safety and comfort. One of the concerns is that passengers may experience anxiety or fear due to the confined space of tunnels, particularly underwater. High speeds can exacerbate feelings of unease and fear regarding potential accidents, such as derailments, which are often amplified by the enclosed environment.

While other factors, such as evacuation procedures and flooding risks, also play significant roles in operational decisions, the specific concern about passenger perception and psychological comfort underscores why speed limits are enforced. The goal is to create an environment where passengers feel safe and secure throughout their journey, particularly in potentially intimidating sections of a route.