State putting in hundreds of miles of rumble strips

Point out a single six-inch divot scratched into the center of the highway and the casual observer might assume its the beginning of a pothole. Line up millions of them across hundreds of miles of highway and they become an effective life-saving tool called a rumble strip.

Little more than three weeks ago construction crews contracted through the Montana Department of Transportation began a 12-week project to cut center line rumble strips into 820 miles of roads stretching from Lincoln to Harlem and from Babb to Belt.

Not quite sure what a rumble strip is? If you've happened to cross over one traveling at high speeds down the highway, you'd remember.

A loud repetitive sound like a high-speed jackhammer threatening to pound through the bottom of your car jolts into your consciousness. A startling vibration accompanies the noise, telescoping through the steering column.

It's hard to ignore - and it's supposed to be.

"I call it an audible warning device," said Roy Peterson, MDT traffic and safety engineer. "It's telling the driver, 'You're drifting.' It's kind of like an alarm system on the highway."

According Montana Highway Patrol statistics, about 12 percent of all the traffic deaths in Montana are due to motorists inadvertently drifting across the center line while falling asleep, playing with their phones, adjusting the radio or just plain not paying attention. Rumble strips are designed to alert motorists to that peril, and save both their lives and those of people traveling in the opposite direction. 

"In Montana and a lot of other states a high percentage of our fatal and injury crashes are due to folks leaving their lane of traffic," Peterson said. "To the right, more times than not it ends up being a rollover or a fixed object crash. To the left a head-on, sideswipes and sometimes they get all the way over to the other side of the road and rollover and eject. We have folks traveling long distances at high speeds where people may be getting sleepy or are distracted by cell phones."

"Rumble strips are a low-cost, systematic safety measure that will save many, many lives I feel," he added.

The data back him up.

Rumble strips are a long way from being a new technology. New Jersey's highway department began experimenting with them in the early 1950s, and over the past 65 years numerous highway safety studies attest to their effectiveness.

A 2015 report from the Federal Highway Administration found that on average, center-line rumble strips reduced head-on and sideswipe crash injuries and fatalities by 47 percent. In Montana that would equate to 12 fewer deaths and 127 fewer serious injuries each and every year.

Rumble strips have proven especially effective when driving conditions are less than ideal, such as when a blanket of snow covers the roadway or when heavy rain or fog obscure the center line. You may not be able to see it, but you're definitely going to hear and feel it.

Shoulder rumble strips are now a common feature on most Montana highways. The MDOT is now in the midst of a five-year project to grind out center-line rumble strips across the majority of Montana by the winter of 2019.

However, not every motorist is in love with them. 

Rubbing across a rumble strip can be startling. Will it damage my tires? What about motorcyclists and bicyclists? Are they at greater risk of losing control when coming in contact with purposely gouged driving surfaces?

"We used a lot of other states' experiences with regard to maintenance, with regard to motorcycles, how it would affect winter driving," Peterson said. "We were not able to find any issues. In fact some motorcyclists said as long as they're aware of them, the suspension on the motorcycles are able to handle these. There was nothing that had a clear example of where rumble strips created an issue with motorcycles."

As for tire damage, if a motorist were to consistently drive hundreds of miles with their tires straddling the rumble strips, it might cause a problem - but why would anyone want do that. The entire purpose of rumble strips is to get motorists back into their lane. If you're endlessly driving across them your primary concern should be your risk of having a head-on collision, not the potential damage it might be causing to your tires.

"One of the things with regard to the public feedback is that our rumble strips might be a little aggressive." Peterson said. "In our state, we chip seal our roadways, so if we make them too shallow and we chip seal, then you lose any effectiveness. You have to then re-cut them back in."

There is a morbid irony in the fact that the greatest risk posed by rumble strips may be to the road crews building them. On the two-mile approach to the construction site on U.S. Highway 87 north of Loma, most motorists slow and zipper their vehicles into a steadily advancing line of cars and trucks.

A few drivers ignore the warnings, and see the slowing traffic as an opportunity to race ahead and gain a meaningless advantage at the risk of other peoples' lives. One car comes dangerously close to racing into the cluster of workers and equipment straddling the highway's center line.

"Please be patient," pleads Bess Doren, engineering project manager for the Highway 87 project. "We really need people to slow down and watch for the crews out there, and for the other drivers so we can get everybody through our workzones safely."

That's the goal both before and after the rumble strips are installed.