At the beginning of the 21st century, Malaysia's capital faced two simultaneous daily nightmares: endless traffic jams paralyzing the southern metropolitan area and devastating flash floods caused by monsoons overflowing the Klang and Gombak rivers. The conventional solution required building a multimillion-dollar drainage canal and an underground road tunnel separately. Instead, engineers devised a pioneering hybrid solution: the SMART Tunnel (Stormwater Management and Road Tunnel).
Opened in 2007 with a length of 9.7 kilometers, the tunnel's core integrates a two-level toll motorway nestled within its 4-kilometer central section. The key to this colossal reinforced concrete structure lies in its modular versatility regulated by automated hydraulic gates operating in three modes:
- Mode 1: Under dry or light rain conditions, vehicles travel normally across both highway decks.
- Mode 2: During moderate storms, floodwaters are diverted exclusively through a sealed lower channel, allowing traffic to continue flowing on the upper platforms.
- Mode 3: In extreme torrential downpours, the control center activates the emergency protocol. The highway is closed to traffic, and after confirming via thermal sensors and cameras that not a single vehicle or person remains inside, watertight gates open. The entire tunnel transforms into a gigantic aqueduct holding and channeling up to three million cubic meters of water, saving downtown Kuala Lumpur from catastrophic flooding.
After the storm, mechanical cleaning and disinfection crews restore the asphalt to reopen the road to traffic in under 48 hours, establishing the tunnel as one of the world's most elegant and celebrated urban engineering works.
Source: Institution of Civil Engineers (ICE) / SMART Motorway Control Centre, Malaysia
