The speed limit on the Hood River-White Salmon Interstate bridge will be lowered to 15 miles per hour starting on Thursday.  Port of Hood River Commissioners decided to implement the speed reduction a month ago as one immediate action to help extend the serviceable life of the nearly 100-year-old steel structure until a replacement bridge is constructed.  The Port’s consulting bridge engineers have advised that two main factors cause accelerated deterioration to the bridge deck – vehicle speed and weight.  Port crews will install new speed limit signage on the bridge on Wednesday, including digital radar speed signs.