KANSAS CITY, Mo. — Drivers may have thought they were hearing things when a robotlike voice invaded their cars as they traveled an interstate north of the city last fall.
It wasn’t their imagination.
State highway workers had beamed a message through a “sound cannon,” a high-tech gizmo that allows communication over long distances under noisy conditions.
Researchers developed it for the U.S. military to warn strangers getting too close to ships. Since then, it’s been used to protect convoys in Iraq, warn pirates on the high seas to go away and disperse civilian demonstrators in New York and Pittsburgh.
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And last year, a Missouri highway worker figured the unit could come in handy at highway work zones, as a way to warn distracted motorists to slow down and move over.
He contacted the manufacturer, which loaned the Missouri Department of Transportation (MoDOT) several of the long-range acoustic devices, or LRADs, for testing.
Researchers wheeled the units out on department vehicles on Interstate 435 and on Interstate 70 near Columbia in November.
“The whole idea is to prevent crashes into our mobile-work zones,” said Chris Redline, assistant Kansas City district engineer with the department.
Although the project has been shelved for now, MoDOT officials remain interested in how the devices could protect highway workers. They are waiting on results of a $49,000 University of Missouri study, paid for by federal planning and research funds, that are expected soon.
The device’s manufacturer also is interested. MoDOT apparently was the first to suggest using the devices on highways, a company spokesman said. Now, the company is considering marketing the unit to highway departments across the country.
One challenge would be overcoming complaints by people who oppose the device’s use, said E. Brian Harvey, a spokesman for LRAD, the San Diego-based company that introduced the device after a terrorist attack on a Navy vessel in a Yemeni port killed 17 sailors in 2000.
About a dozen bloggers who recently heard about the MoDOT testing have lamented an Orwellian future of transmitted voices startling drivers inside their cars. And last month, lawmakers in Jefferson City questioned whether MoDOT had spent money on the devices without getting legislative approval. It hadn’t.
One thing is certain: The LRADs are startling at first glance.
The model mounted in the rear of MoDOT trucks resembled an orchestra’s timpani, tilted about 90 degrees to directly face drivers. When a vehicle came too close to the truck’s rear, drivers heard a high-pitched sound and the message “slow vehicles ahead.”
Researchers used sound levels within standards recommended by agencies such as the National Institute for Occupational Safety and Health, said Henry Brown, a University of Missouri traffic engineer.
The instrument, he added, appeared to perform as MoDOT officials had hoped, by prompting drivers to move over a lane. The average merging distance with the LRAD was greater from the truck than the average distance without it, he said.
Highway officials had pondered a pilot program this spring, but they postponed it because the devices were unavailable, said Holly Dentner, MoDOT spokeswoman.
Meanwhile, MoDOT officials continue to adopt ways to better protect workers. They have installed cushioning devices and elaborate lighting systems on trucks, for example.
Over the last two years, motorists have hit MoDOT work crews 44 times, Dentner said, and 16 employees have died on the job since 2000.
The possible use of the device in Missouri should not alarm drivers, said Harvey, the LRAD spokesman.
“We saw all the social-media postings and we were surprised about how it was being perceived,” he said.
“The reality is that these are high-powered speakers which are used predominantly as a communications tool.”
One Columbia resident, however, is wary about encountering an LRAD on a Missouri highway.
Karen Piper, an English professor at the University of Missouri, served as a visiting faculty member at Carnegie Mellon University in 2009. That September she observed demonstrations during the G-20 economic summit in Pittsburgh.
The police deployed an LRAD to communicate with and disperse demonstrators.
“I didn’t even know it existed,” Piper said. The sound it transmitted, she said, “was a high, screeching, sirenlike sound, very loud and painful.”
The American Civil Liberties Union of Pennsylvania sued the city of Pittsburgh, maintaining that Piper had suffered permanent hearing loss, nausea, pain and disorientation.
Piper received a $72,000 settlement in 2012. She continues to have hearing loss in one ear that makes it difficult for her to distinguish some consonants, she said. She wonders whether drivers one day could suffer injuries similar to hers.
“I don’t think they should use it at all,” Piper said.
“It has that siren built into it, and maybe people will be tempted to use it. And that’s dangerous.”