Changes big and little make highways safer
Staff writer
This week marks the 10th anniversary of one of the most life-altering developments in Marion County.
No, it wasn’t the opening of a charity, a health-care center, a service organization, or even a business.
It was creation of a twisted stretch of pavement northeast of Marion — the US-56/77/K-150 roundabout.
What had been classified as the single most deadly intersection in Kansas almost immediately became one of its safest — a virtual repeat of what happened in Florence several years earlier when the US-50/77 roundabout was installed there.
Both are among a range of improvements — some big, some small — that have made highway travel much safer.
“KDOT doesn’t figure them out all on their own, of course,” Brent Terstriep, district engineer for north-central Kansas, told the Record, but it’s always experimenting. “Learn from the past so you don’t make the mistakes again and use the taxpayers’ money wisely.”
Options about reducing speed or closing some access roads during impending reconstruction of US-56 might seem controversial, but Kansas Department of Transportation traffic engineers have a long record of improvements that have made highways measurably safer.
Since the Marion County roundabouts were installed, fatalities and serious accidents at the US-50/77 and the US-56/77/K-150 intersections have largely been eliminated.
And the cost has been less than half what it would have taken to build a complete overpass instead.
Not all states use roundabouts They’re among the many ideas highway engineers in Kansas continually think about, experiment with, and adopt.
Roundabouts are based on a horse-and-buggy-era idea — traffic circles common in Europe for decades.
But there’s a key difference. In a traffic circle, vehicles approach at 90-degree angles and have to turn into the circle pretty much as they would in a normal intersection.
In a roundabout, vehicles gradually merge at an angle into the flow of the circle.
“If you did have a crash,” Terstriep said, “you would be more side-impact than you would at a T like a traffic circle.”
One of the tools engineers use to study highway safety is mapping out the number of “conflict points” where crashes could occur.
“With a roundabout, you reduce those conflict points,” Terstriep said, “and on top of that you put it as a side impact vs. a T-bone.”
In addition to delivering only glancing blows, vehicles also travel much more slowly through a roundabout.
The impact of roundabouts has been without question. But so, too, have other seemingly minor changes.
“It’s a combination of many things,” Terstriep said. “I mean, no one thing is going to solve everything.”
One of the most important, already present on US-77 and US-50, are rumble strips down the centerlines and edge or fog lines of highways.
“People on the road — they have to pay attention. That’s a big part of it,” Terstriep said. “We can’t help that they don’t pay attention. We can put rumble strips out, help guide them or let them know that they’re not on smooth pavement anymore and they might want to wake up.”
The strips, which are being installed on highways like US-56 as they are repaved, alert drivers who might have been distracted or dozed off that they are about to veer off the road or into oncoming traffic.
“As part of new surfacing projects, we do put them up to date on the rumble-strip installation,” Terstriep said.
The strips help address what Terstriep said was the biggest change in traffic safety in recent years — not bigger or faster vehicles but more distracted drivers.
“I see a lot of accidents,” Terstriep’s colleague, north-central public information officer Ashley Perez said. “A lot of it is distractions. You know, phone, eating while driving. I mean there’s a lot of distractions that play a big part in safety.”
It took some tinkering for engineers to figure out exactly how to do rumble strips.
Originally, they were bits of asphalt or other material added to the top of roadways — much like speed bumps and rumble strips before stop signs or pedestrian crossings.
“They would rise up,” Terstriep said, “and then our snowplows would not like those very much. So, we would learn over time it’s a little better to mill them in. And that’s what we do.”
A more easily recognizable improvement has been the addition of passing lanes. US-50 in Marion County now features many of them, and under current plans at least one set of passing lanes is planned for US-56 near Marion Reservoir.
They can’t be added everywhere. Extra-wide right-of-way with ditches distant from the roadway are necessary to avoid costly purchasing and regrading of land.
With rumble strips and passing lanes, the deadliest type of wreck — head-on collisions — have greatly been reduced.
Also impacting safety are more numerous and longer turn lanes and acceleration lanes at intersections. They are among many improvements planned for US-56.
So, what else is next?
“There are lots of things we can do,” Terstriep said, “like wet-reflective pavement markings. We do trials on things to see how well they work and trade off one thing for another — find a pavement marking that shines at night like bright as you could ever imagine in the rain, but in the day look like it’s not even there.
“So, there are tradeoffs when you want to fix this problem, but you want to maintain what you already have. So, we do try out different things.”
One of the “new things” tried out when US-56 was installed north of Marion and Hillsboro nearly 40 years ago was something that involved periodic drilling into newly laid concrete and inserting reinforcing rods.
Concrete highways used to be installed in sections 61½ feet long. Now, concrete pavement is installed in sections twice the number of feet in length as the pavement is inches in depth. So, an 8-inch payment would be laid in 16-foot sections.
“What was done on US-56 was what’s called dowel-bar retrofitting,” Terstriep said. “We cut slots and put dowel bars in. That’s a load-transfer device designed to help that pavement from getting worse. But it does cause some longitudinal cracking.”
Wider shoulders “absolutely” are an important part of increasing roadway safety, he said.
“A lot plays into shoulder width,” Terstriep said. “Paved, three-foot shoulders are a very cost-effective improvement when you have the embankment already there. If you have a hard shoulder out there, you can also have rock. But it’s a maintenance thing, bringing up that rock all the time.”
Self-driving cars still are a long way off, Terstriep said, but “some of the features on the cars do help — like the lane-keep, adaptive cruise control, auto-sensing headlights — because we do have a lot of distracted driving.
“Is it a crutch? I don’t believe you asked me that.”