The honeymoon was almost over for Steven Lavrenz and Sandhya Madan. After sightseeing in Acadia National Park, the newlyweds from Michigan woke early and started a long drive back to Boston Logan International Airport on the gray morning of June 3, 2019.

But they wouldn’t get very far before their trip — and their lives — were nearly upended.

Heading north on Route 102, Lavrenz noticed a red pickup truck on the other side of the thoroughfare veering toward his Subaru rental car. Growing up in Iowa, Lavrenz had always held his breath on these kinds of two-lane rural roads, keeping one eye on oncoming traffic to ensure passing cars stayed in their lane.

So when the Nissan crossed the centerline, Lavrenz was quick to react, swerving away from the approaching vehicle. The maneuver may have saved his life: The truck crashed into the door just behind Lavrenz, totaling the car but leaving him physically unscathed.

Madan and the truck’s driver also escaped the incident without injury, which is fortunate after what transit experts call a “lane-departure crash.” While representing just 30 percent of Maine’s traffic collisions between 2010 and 2022, lane-departure crashes accounted for 73 percent of fatalities.

These head-on and sideswipe collisions are especially deadly in Maine, where researchers say that extreme weather, an aging population and infrastructure and a preponderance of winding, two-lane rural roads contribute to the highest crash fatality rate of any state in New England.

Though Lavrenz was physically unharmed, the crash rattled him for a different reason than most. As a transportation safety researcher, he’d spent years thinking about lane-departure crashes and trying to prevent them from happening. But it was the first time the Wayne State University professor had ever personally faced the life-or-death consequences of his profession.

Lavrenz had once worked with the Federal Highway Administration to add rumble strips to rural roads. Transportation departments around the country have gradually installed these grooved lines to jolt drivers who are asleep or distracted, the most common causes of lane-departure crashes. The strips vibrate the vehicle when it passes over the centerline or into the shoulder. 

Yet there were no rumble strips on this stretch of Route 102 that could have stirred the distracted truck driver, Lavrenz observed after their destroyed Subaru sputtered to a stop next to a Maine Department of Transportation facility. The next morning, after they secured another rental car and caught their flight, he decided to tweet at the agency.

“Centerline rumble strips could’ve prevented this,” he wrote, linking to a dashcam video of his crash.

Research from a bevy of states backed his assertion at the time. But a new study led by civil engineers at the University of Maine provides the most relevant data yet for the effectiveness — and cost-effectiveness — of centerline rumble strips on Maine’s sprawling network of rural roads, many of which remain without these life-saving grooves.

In a before-and-after analysis, the researchers found that installing centerline rumble strips on rural two-lane roads reduced head-on and opposite sideswipe collisions by anywhere from 28 to 48 percent. By limiting these dangerous crashes, the state saves not only lives but money, according to the authors, who estimated that “the benefits of the rumble strip installations are at least 14 times the cost.”

“They’re one of our most cost-effective safety countermeasures that we can deploy out there — and also one of the most effective,” said Bob Skehan, the director of MaineDOT’s Office of Safety and Mobility.

Jhan Kevin Gil-Marin, one of the study’s co-authors, started working on the paper as a master’s student in civil engineering at the University of Maine. With guidance from Ali Shirazi, who was then the principal investigator of the Maine Transport Lab based at the school, Gil-Marin used data from MaineDOT to compare crashes on similar roads with and without rumble strips.

Unlike some past analyses in Maine and elsewhere, however, the study examined before-and-after crash data on roads specifically with centerline rumble strips. And it used these figures to model how many crashes would ensue if the grooves had never been installed on them, allowing the researchers to better determine the safety measure’s true effectiveness.

It also enabled them to perform a cost-benefit analysis, calculating this number based on MaineDOT’s reported installation cost ($3,500 per mile, according to the study, though Skehan said it can now be higher) and the Federal Highway Administration’s assigned costs for different types of crashes. Even using a very conservative service life for rumble strips of seven years, the study showed the strips pay for themselves and then some.

“I think rumble strips are a very good idea,” said Gil-Marin, who’s now pursuing his PhD at Rensselaer Polytechnic Institute.

Before uprooting to Maine from Colombia to work with Shirazi, Gil-Marin had never seen rumble strips. On a quiet road, he guided his car over the grooves and felt the vibration for the first time.

It wasn’t long ago that many Mainers may have had the same experience.

Getting ready to rumble

When Per Gårder arrived in Maine in 1992, there were no rumble strips in the state. During the Swedish engineer’s interview for a position at the University of Maine, however, he met John Alexander, a fellow engineer who’d taken a personal interest in the safety measure. A neighbor of Alexander’s had died after driving off the interstate and hitting a tree. 

“He started talking to me about installing rumble strips by driving a bulldozer down the highway and roughing up the shoulder so that people would wake up before they go off the road,” recalled Gårder, a professor emeritus of civil and environmental engineering and co-author of the new study.

Road safety was personal for Gårder, too. As a kid, he recalls one trip when his sleepy father ceded the wheel to his mother late at night. When Gårder woke up, they were in a ditch — his mother had dozed off. “We didn’t hurt ourselves, but that was probably the first time I started thinking there should be [something on the road] waking you up when you are drifting to sleep, and that it actually could happen to everybody,” Gårder said.

After Gårder joined the faculty, he made shoulder rumble strips a focus of his research. There were few studying it at the time. In the U.S., “singing shoulders” debuted on the Garden State Parkway in New Jersey during the 1950s, but they were rarely seen elsewhere for decades. MaineDOT and the Maine Turnpike Association didn’t start installing rumble strips along the edges of Interstate 95 in Maine until 1994.

In his early years at the school, Gårder photocopied and analyzed police reports of fatal crashes on Maine’s interstates between 1989 and 1993, which revealed that nearly half of them involved drivers falling asleep. Yet, after the installation of hundreds of miles of continuous shoulder rumble strips along Maine’s interstates, driver drowsiness was no longer as deadly; an analysis co-authored by Gårder in 2006 showed that the safety measure had reduced sleep-induced “run-off-road” crashes by 58 percent.

That same year, MaineDOT began installing rumble strips on the centerline of state roads. While the addition of the safety measure to the shoulders of interstates had helped prevent drivers from veering off the interstate, implementing rumble strips in the middle of rural thoroughfares could reduce the often lethal head-on collisions between cars in opposite lanes.

“When you have two vehicles traveling at 50 miles an hour that hit head on, essentially, it’s the same as being in a 100 mile an hour crash and hitting a fixed object, like a tree, if you went off the side of the road,” Skehan said. “So they’re definitely our biggest risk from a safety perspective.”

Initially, the agency targeted corridors with a speed limit of at least 45 miles per hour and a traffic volume of more than 8,000 vehicles per day to add rumble strips. The pilot produced excellent results: the new rumble strips on these roads cut head-on crashes in half and eliminated fatal collisions entirely during an initial period, Skehan recalled.

That level of effectiveness wouldn’t quite hold up over the long term. And as MaineDOT installed more rumble strips in areas where head-on crashes were common, there were still some deadly collisions even after the safety measure was implemented.

But time after time, the little grooves significantly reduced crashes and fatalities.

“It’s still, by far, our biggest lifesaver with regards to two-lane, rural, head-on collisions,” Skehan said.

He pointed to a 20-mile stretch of Route 202 between Lewiston and Manchester where head-on and sideswipe collisions dropped precipitously in the three years after the installation of centerline rumble strips about a decade ago.

“It was pretty remarkable,” he said.

Still, part of what made rumble strips so effective also disturbed more than a few neighbors when they were first installed on rural roads. 

“There were some noise concerns,” Skehan said.

After MaineDOT added rumble strips to Route 302 in Bridgton, neighbor Bill Muir compared their clamor to a tractor trailer “going down a steep grade and shifting into low gear.” 

“I know from personal experience that it could be heard inside our home quite clearly even with all windows closed,” Muir wrote to The Bridgton News in February of 2017.

The next year, MaineDOT began exclusively using sinusoidal rumble strips, colloquially known as “mumble strips.” When they’re driven over, the quieter, shallower alternatives to rectangular rumble strips create slightly less sound inside the car but drastically decrease the noise outside of the vehicle, according to Skehan.

“That has pretty much eliminated all noise calls that I’ve received.”

Looking down the road

Rumble strips now line the edges of all interstate highways in Maine. But centerline grooves remain absent from most roads in rural areas, particularly in the northern part of the state.

MaineDOT aims to add about 100 miles of rumble strips to state roads every year, according to Skehan. The agency prioritizes areas with high traffic and fresh pavement to maximize the service life of the grooves. MaineDOT allocated about $750,000 for these projects annually, per Skehan, with about 90 percent of this funding coming from the federal Highway Safety Improvement Program funding, and the remainder from the state.

Route 102 doesn’t have rumble strips yet. It’s a candidate to receive them, according to Skehan, but the area where a truck crashed into Lavrenz and Madan’s rental car is less of a priority than other corridors.

The state also doesn’t manage town and city roads that thread through communities. Bar Harbor police chief David Kerns doesn’t see much of a need for rumble strips on these generally lower-speed roads.

“Really, those in-town streets are so narrow anyway, people tend to go center of the road more to get away from parked cars and open doors,” Kerns said.

Still, he’s noticed a rise in collisions he attributes to the distraction of cell phones and displays in cars.

The town of Bar Harbor received a federal grant to make its streets safer after five fatal and 17 incapacitating crashes between 2019 and 2023. Additional signage and collapsible line delineators are among the interventions under consideration.

At the same time, Kerns recognizes that technology can also be part of the solution. Some cars are now built with sensors to detect when the vehicle has left its lane. And though Gårder doesn’t advocate checking your phone while driving, he stresses glancing at displays every once in a while to stave off sleep, which is still a common cause of crashes.

“Like in an airplane, pilots are supposed to have certain tasks every now and then,” he said. “They are not supposed to be completely inactive.”

For Lavrenz, it’s simple: “Human drivers are always going to make a mistake.” And instead of waiting for crashes like his to happen, transportation departments can address the problem proactively by deploying low-cost safety measures like rumble strips across many miles.

“Let’s go out and try to treat a broad swath of these two-lane rural roads because we know that they’re a major risk factor,” he said, “and hopefully prevent a lot of these crashes from happening in the first place.”

This story was originally published by The Maine Monitor, a nonprofit civic news organization. To get regular coverage from The Monitor, sign up for a free Monitor newsletter here.