New road design to be tried

Missouri 5 will get an experimental lane layout designed to ease delays.
Wednesday, July 18, 2007 | 12:00 a.m. CDT; updated 12:28 p.m. CDT, Monday, July 21, 2008

CAMDENTON — Hurry up and slow down. Everyone who has ever driven a busy two-lane road knows this frustration: You wait miles for a break in oncoming traffic to pass a slower vehicle, only to get slowed down again by another caravan of cars and trucks.

Some two-lane roads have occasional passing lanes, for example when heading up a big hill. But short of four-laning every road, there’s only so much the state highway department has been able to do.

Until now.

The Missouri Highways and Transportation Commission today is expected to approve what apparently will be a model project nationally — a hybrid of normal two-lane and four-lane roads in which a passing lane will alternate every mile or so between the north and south lanes.

The $50 million experiment is planned for a 16-mile stretch of Missouri 5 between Lebanon and Camdenton, a twisting and sometimes slender two-lane road that connects Interstate 44 to the Lake of the Ozarks.

The concept of a continuously alternating passing lane has been used for years in parts of Europe, which is where Missouri’s chief highway engineer came up with the idea. But it’s so new in the United States that transportation officials haven’t agreed on what to call it.

The Missouri Department of Transportation markets it as a “Shared Four-Lane Highway.” The American Association of State Highway and Transportation Officials calls it a “2+1” road.

Jim McDonnell, AASHTO’s deputy program director for engineering, said the Missouri project is believed to be the first one getting under way in the U.S.

American transportation officials, after a European road tour, concluded that “2+1” roads there were effective in rural areas at addressing both safety problems and traffic congestion.

“You get almost the same traffic volume and safety benefits of a four-lane highway. That’s the theory,” said Kevin Keith, MODOT’s chief engineer.

Missouri 5 averages 8,000 vehicles a day — enough to justify a four-lane road under MODOT’s historical benchmarks, Keith said. In fact, a four-lane road was promised as part of the state’s 15-year road plan adopted in 1992, but it never was built because the state lacked the money.

The alternating passing lanes can be built at half the cost of a four-lane divided highway, Keith said. Construction is scheduled to begin by next summer and be completed by mid-2010.

The project is being added to Missouri’s $5 billion, five-year highway plan.

The Missouri 5 project is the only “Shared Four-Lane Highway” in the department’s plans. But if it works well, it could serve as a model for the future, Keith said.

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