The fragility of Perth's transport network was laid bare again yesterday when a single power line tangled around the top of a moving train, forcing rail services to a halt and stranding thousands of people.
The driver told commuters on the 7.31am Perth-bound train from Joondalup they faced "a life-threatening situation" after the snapped powerline whipped the carriage shortly before 8am.
The line slammed against the train and broke a window. There were unconfirmed reports that small debris from the train's pantograph - the apparatus that connects the train to the wire - flew on to the Mitchell Freeway.
Electricity to the 25,000-volt line would have cut immediately but residual power would have made the line "live" for several seconds.
The 200 commuters on the train were told not to leave it until the outside area was secured. An hour later they were allowed to disembark and board buses to take them into the city.
More than 1.5km of line and other minor rail infrastructure was damaged and repairs will continue today with normal rail services not expected to resume until tomorrow.
Extra buses have been organised to transport commuters this morning and, if required, this afternoon.
Trains will continue to operate between Clarkson and Whitfords and the city and Stirling.
Mitchell Freeway traffic was also congested, with the right lane northbound between Karrinyup Road and Erindale Road closed for most of yesterday.
It is the third time in five years that powerlines have tangled around pantographs on a Perth train.
In both previous instances - on the Mandurah line in 2008 and at the Gosnells station in 2010 - the cause was never determined despite investigations.
In Melbourne in 2010, an overhead wire became tangled in the pantograph and an investigation found that a frayed supporting wire had snapped. It was blamed on a poor inspection regime.
Transport Minister Troy Buswell described yesterday's incident as a significant event with "dire consequences" for commuters.
He said a full investigation was under way that could ultimately involve the Office of Rail Safety.
Public Transport Authority spokesman David Hynes said the commuters were never at risk of electric shock.
"Even if the live wire was sitting on top of the train, there was never any risk to passengers as long as they stayed in the train," he said.
Mr Hynes said the lines were inspected regularly.
The incident comes only six months after a small, early-morning fire on the train network near Barrack Street forced the Fremantle to Perth line to close and city services from Armadale and Midland to be cut severely. As a result, city commuters took their cars and clogged main roads.
A week later, thousands of passengers were again hit with a major disruption when an electrical fault caused services on the Fremantle line to be cancelled for three hours.
Also yesterday, services on the spur line between Cannington and Thornlie were cancelled because of an unrelated technical issue.