WSDOT: Truck drivers often ignore bridge clearance sensors

by: Graham Johnson Updated:

Simpson Avenue Bridge

Three state bridges have sensor systems to warn trucks with overheight loads about low clearance, but the Washington State Department of Transportation says truck drivers too often ignore them.

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 an I-5 overpass in Chehalis.

Even with the warning system, an overheight truck struck the I-5 overpass in Chehalis on May 22.

WSDOT Region Operations Engineer Chris Keegan says three overheight 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 overheight load strikes.

"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.

A Purdue University study indicates sensor systems like those in Washington cost between a few thousand dollars and $25,000. Keegan said there are not currently plans to expand the use of sensors.

Keegan said they 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.