Operational Modes


Operational Modes of The Smart Tunnel


When weather is fair with little or no rain and traffic is allowed in the tunnel


  • Activated when moderate rainfalls and the flow rate recorded at the confluence of upper Sg. Klang/Sg. Ampang (L4 flow station) is 70-150 m3/s.  Only 50 m3/s is allowed to flow downstream
  • Excess flood water will be diverted to SMART storages and only the lower drains of tunnel will be used to convey flood flow to the Desa attenuation pond
  • Road tunnel will still be opened to traffic


  • Activated when major storm event occurs and flood model forecasts a flow rate of 150 m3/s or more at L4
  • Traffice will be evacuated from the road tunnel.  This normally takes about one hour.  Only 10 m3/s is allowed to flow downstream
  •  If heavy rain storm stops early or due to some specific circumstances, then the traffic tunnel will not be flooded
  • Road tunnel will be re-opened to traffic within 2-8 hours after closure


  • Activated if heavy rain storm prolongs, usually will be confirmed 1-2 hour after Mode 3 is declared
  • Road tunnel will be used for passage of flood after traffic evacuation completed.  Only 10 m3/s is allowed to flow downstream
  • Road tunnel will be re-opened within 4 days of closure