I’ve heard from a few drivers today, reporting seeing falling chunks of ice coming from the cables on the new Port Mann bridge, landing on vehicles below…A similar situation resulted in a bridge closure for a period of time on the Tacoma Narrows bridge last winter.
* as of 1:50 pm, RCMP have closed the bridge, Scan BC is reporting one person knocked unconscious by falling ice requesting ambulance.
**** update : Susana Da Silva of CBC is tweeting no reason to believe Scan BC reports above – Approx 5 reported to RCMP and two injuries.( Not sure everyone is going to report to RCMP if only cracked windshield or broken mirror – so will be interesting to follow pictures online- many coming across twitter aready)
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A tragic development to this bridge,but lets look at two things.
I’m not an engineer, but when you look at the design of the bridge, with a central support column employing cables as support… those cables are suspended from the central support and do cross over the lanes of traffic below.
Clearly, any ice or snow that accumulates on those cables has to go somewhere – and at that height, speed and any wind force becomes a factor on where that ice is going to fall and how hard it is going to hit anything below.
Unfortunately, it seems we now know it will fall directly onto the lanes below, filled with vehicles and unsuspecting drivers.
More often we see bridges with cables that run parallel to the roadway to the side, which minimizes that falling ice hazard, except in winter weather combined with high winds that can cause ice or snow to be carried sideways back onto the road.
The question becomes then, what – if any – design elements, de-icing or anti-icing technology or methods were employed to prevent this, knowing the cables would cross over traffic below?
Update Dec 20th,
Great youtube dash cam video of snow/ice falling from cables above… look how often and how far..