The bridge that was destroyed when struck by an oversized load in Washington State last week had a sensor system to warn trucks with over-height loads about the low clearance, but the Washington State Dept. of Transportation (WSDOT) claims truck drivers often ignore the warnings.
According to a KIRO TV news report, three state bridges have sensor systems to warn trucks with over-height loads about low clearance.
On the Simpson Avenue Bridge in Hoquiam, warning lights flash if a high load breaks the beam between two sensors. The State says a horn used to sound, but it was disconnected after neighbors complained about the noise.
There are similar systems on the State Route 529 bridge in Everett and the I-5 overpass in Chehalis that collapsed when struck by an over-height truck on May 22.
According to WSDOT Region Operations Engineer Chris Keegan, three over-height loads struck the Simpson Avenue Bridge in 2011, and five in 2012. Last fall, WSDOT raised the clearance on the bridge by nearly two feet because of over-height load strikes.
Keegan said the warning systems often produce false alarms when something other than a truck breaks the beam between sensors. Birds, flapping tarps and even snow have created false alarms.
"We know there are these low points, we know we can't afford to replace them, we're trying to find a less expensive means of preserving the bridges," Keegan said of the warning systems.