Devices and early warning methods used to reduce hits on low-clearance structures

Oregon DOT has used an overheight vehicle warning system with two light sources and detectors mounted on poles on both sides of the roadway. When an overheight vehicle passes through and breaks the beam of light, an audio alarm sounds. There is also an illuminated warning sign used in advance of the alarm to advise drivers of the alarm.
ODOT has an approved system on their QPL.