An official watchdog in the US has called for a nationwide probe into systems designed to cope with smoke incidents in tunnels.
The National Transportation Safety Board (NTSB) urged the Federal Transit Administration (FTA) to assess a range of safety factors related to fires in enclosed spaces.
Its report comes alongside a specific and ongoing investigation into a smoke accident in Washington DC last month.
The NTSB recommended a nationwide audit of transit agencies to assess: the state of tunnel ventilation systems; written emergency procedures for fire and smoke events; and relevant training.
It also called for the FTA to verify that agencies were applying best practice in maintenance and emergency procedures.
The NTSB said that a southbound Washington Metropolitan Transit Authority (WMATA) Metrorail train stopped at 3.15pm EST on 12 January after encountering heavy smoke in a subway tunnel between the L’EnfantPlaza station and the Potomac River bridge.
As part of an ongoing investigation, the NTSB found that WMATA did not have the means to determine the exact location of a source of smoke in its tunnel network.
NTSB said WMATA maintained no written ventilation procedures for smoke and fire events in the tunnel. The watchdog added that the ventilation strategy that WMATA implemented during the accident was not consistent with best practices.
The WMATA welcomed the NTSB recommendations and said it had begun to address them.
A spokeswoman said: “Following the 12 January incident, we conducted systemwide inspections and tests of all tunnel fan shafts and found them to be in good working condition.
“We also completed familiarisation training for all 39 controllers in our rail control center and we are reviewing additional protocols and training associated with tunnel fan use that are responsive to the NTSB recommendations issued today. We continue to give our full cooperation to the ongoing NTSB investigation.”