STEVE INSKEEP, HOST:
You may see this when you're driving: signs and even flashing lights tell you to slow down when you are in a work zone. But even with such warnings, in just the past five years, just in the State of Missouri, 53 people have been killed, and almost 3,000 injured in road work zones. Now Missouri officials are looking at deploying harder-to-ignore methods to get drivers to slow down.
Kristofor Husted of member station KBIA reports.
KRISTOFER HUSTED, BYLINE: As Wednesday's rush hour dies down on Interstate 70 in Columbia, Missouri, Scott Campbell is merging onto the highway.
(SOUNDBITE OF ALARMS)
SCOTT CAMPBELL: Off like a herd of turtles.
HUSTED: Campbell is with Missouri's Department of Transportation, and he's spending the night here with the maintenance team to repaint the yellow stripe in the fast lane. The caravan of trucks with mounted signs, flashing arrows and bright lights, spreads out for more than a mile, creeping along at 10 miles per hour. Even with all these emblazoned alerts, Campbell was struck by a pickup at a worksite two weeks ago.
CAMPBELL: I heard screeching tires, and looked back and saw him sliding into me. And I just waited for the impact, basically. He left 120 foot of black marks, skid marks before he hit me.
HUSTED: Fortunately, both Campbell and the driver walked away from that accident. State maintenance engineer Beth Wright says these crashes are becoming far too common.
BETH WRIGHT: With the crashes that we've had, there's no way they were looking at us and not put on their brakes before they hit us. So that means they are doing something else at the same time.
HUSTED: So it appears flashing lights and signs just aren't enough. Next up: A new, very loud approach.
UNIDENTIFIED MAN: Slow vehicles ahead.
(SOUNDBITE OF AN ALARM)
UNIDENTIFIED MAN: Slow vehicles ahead.
HUSTED: The state borrowed a Long Range Acoustic Device, or LRAD, which is essentially a massive speaker used for communication by the Navy. The device looks like a flattened searchlight with a speaker screen. You can tilt it and adjust its volume. The LRADS pump out a concentrated beam of sound in a 15 to 30 degree cone for distances up to an astonishing seven miles.
University of Missouri engineering professor Carlos Sun tested these sonic signals at volume levels in line with occupational safety standards. If you're standing outside of your car 600 feet away from the unit, the sound rings at 78 decibels. That's about as loud as a garbage disposal. Sun says what makes the LRAD more noticeable is its higher frequency.
CARLOS SUN: We found that there was, statistically, a significant difference between the drivers who heard the warning and those who did not.
HUSTED: Sun says drivers exposed to the audible alert slowed down and merged out of the closed lane sooner. But when the department posted a video of the LRAD in action, social media reverberated with outrage and concern.
Brian Harvey, who's with the LRAD Corporation, was confused by the reaction.
BRIAN HARVEY: We saw the blowup of social media, and we were somewhat flummoxed, because we knew what the test was for and the, you know, the reason for the testing.
HUSTED: The alerts gradually increase in volume as drivers approach and dissipate once passed. And because the device produces only a narrow beam of sound, experts say nearby neighborhoods shouldn't be bothered. Even so, Missouri has decided to postpone any trial runs until next year, after officials can do more education and research.
(SOUNDBITE OF VEHICLES)
HUSTED: Back in the truck with Scott Campbell, a few cars have drifted in and out of the closed lane. But so far, it's otherwise been a safe night.
UNIDENTIFIED WOMAN: Scott, are they doing OK?
CAMPBELL: Ah, I just had one take a peak in this lane and move back.
UNIDENTIFIED WOMAN: They're sure slamming on their breaks, but they're not stacking up, at least.
HUSTED: While plans for the LRAD are on hold, Campbell says the maintenance team will become even more cautious of cars running into them.
For NPR News, I'm Kristofor Husted, in Columbia. Transcript provided by NPR, Copyright NPR.