Deep-level tube

A deep-level tube refers to a type of underground railway system that operates at significant depths beneath the surface. Unlike traditional street-level trains or light rail, deep-level tubes are designed to navigate below the city, often running through tunnels that are several stories deep. This design helps to reduce surface congestion and allows for more efficient transportation in densely populated urban areas. These systems are common in major cities like London, where they provide quick public transit options without interfering with ground-level activities.