The Missouri Department of Transportation (MoDOT) announced last week that it would improve safety in highway work zones by startling drivers with an ear-piercing noise. At an event in the Kansas City district headquarters, the agency showed off a Long Range Acoustic Device (LRAD), which is capable of producing an ear-piercing shriek or siren at 153 decibels, which is beyond the threshold of pain and into the territory that causes permanent hearing damage for the driver and any passengers or nearby vehicles.

"The sound easily penetrates the windshield and well-insulated cab of a car, even overriding the vehicle's engine sounds and a radio turned up loud enough to jam to tunes at highway speeds," MoDOT's Michele Compton explained in a newsletter.

LRAD Corporation, maker of the product, claims it can broadcast a loud message in a 15 degree arc over a distance of 1.9 miles. The system was developed for the military for use against terrorists and has been used by law enforcement to disperse crowds of protesters. MoDOT has used the system both mounted on a moving truck and in a stationary position on the side of the road. One test last year had the LRAD truck set off an ear-piercing siren while repeating the phrase, "Slow vehicles ahead" over and over.

Another system used a radar gun to trigger the sound blast in the direction of a vehicle exceeding a certain speed. Each device costs $25,000 and the department has acquired several models.

"We need the right tool for the right place," state Maintenance Engineer Beth Wright said. "I believe it holds promise because it's not extremely loud over distances."

MoDOT is examining whether the device is only to be used in rural areas as the loud noise is likely to disturb nearby neighborhoods and businesses near urban freeways. Missouri transportation officials have been on the cutting-edge in the use of such technologies. Long before the revelation that the National Security Agency has been spying domestically on cell phone use, MoDOT contracted with a firm to track drivers on state freeways using cell phones.