SMART Tunnel

The Stormwater Management and Road Tunnel (SMART) is a 9.7-kilometer dual-purpose infrastructure project designed to solve the city's flash flood problems and alleviate traffic congestion. During normal weather, its lowest deck functions as a motorway for cars. During heavy monsoon rains, it can be completely closed to traffic to channel excess floodwater away from the city center.

The tunnel runs at a maximum depth of approximately 50 meters (about 164 feet) beneath the surface of Kuala Lumpur. This massive depth was necessary to navigate under existing urban infrastructure, rivers, and rail lines. The deepest section of the tunnel houses the massive stormwater holding basin.

The tunnel operates in four modes; in the highest flood mode (Mode 4), the entire road tunnel is completely closed to traffic to act as a massive floodwater drain. Early warning systems and automated gates ensure the road is evacuated hours before water is allowed into the traffic section. No floodwater ever touches the cars while the tunnel is open to the public.

The SMART Tunnel officially opened in 2007 after several years of intensive construction involving massive tunnel-boring machines. It was an ambitious joint venture between the Malaysian government and a private consortium. The project has reportedly saved billions of dollars in flood damage since its inception.