IOWA CITY — With a little paint and re-imagining the use of space, Iowa City officials eliminated two travel lanes from a congested four-lane road — two lanes in each direction — with entrances to a mall, a college campus and factories.
The old traffic stripes were removed. Fresh paint created a center turn lane and one travel lane on each side and room for bikes. The sidewalks were widened, and the city transit bus got a turnoff space in front of Kirkwood Community College.
“It flows pretty well,” said Luci Coconate, 20, of Iowa City, who alternates between busing and driving. “I haven’t seen traffic back up.”
Lower Muscatine Road was put on what transportation planners call a “road diet,” which is a relatively low-cost tool to change the function of streets without reconstruction. Alternative transportation advocates like them because they often embrace cyclists, public transit and pedestrians, while safety advocates say they reduce crashes and improve traffic flow.
Road diets typically involve converting four-lane roads to three lanes with two travel lanes separated by a center turn lane. Designated bike lanes and sidewalks often are layered on the outside of the travel lanes.
The theory is fewer lanes means fewer conflict points, and isolated turning lanes reduce collisions, which cuts down weaving and keeps traffic moving.
The Federal Highway Administration cites studies showing road diets reduce overall crashes 19 percent to 47 percent, with noticeable improvements among drivers under 35 years old and more than 65.
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“Road diets can reduce the vehicle speed differential and vehicle interactions, which can reduce the number and severity of vehicle-to-vehicle crashes,” according to the federal road diet information guide.
Turns and bikes
Keith Knapp, director of Iowa Local Technical Assistance Program at the Institute for Transportation at Iowa State University, said road diets have been used at the local level for years. Knapp said he helped create road conversion guidelines for Iowa in the 1990s.
The Federal Highway Administration included road diets as one of nine proven road safety countermeasures recommendations in 2012 and released a road diet guidebook in November 2014. This may have helped raise awareness about this strategy, Knapp said.
“I would have to think the new information and higher awareness of it makes it at least more of a consideration,” Knapp said.
The Iowa Department of Transportation has embraced road diets through the Traffic Safety Improvement Program, which offers grants worth up to $500,000. Since 2013, the Iowa DOT has awarded more than $3.4 million for 11 project in seven cities with road diets as a key component.
Iowa City has been the biggest recipient of the grants, collecting $1.5 million. Iowa City has been looking at road diets when other road work is being done.
Two new road diet projects are in queue, and at least three more are under consideration.
“The biggest reason is the safety improvements and being able to separate turning vehicles from through vehicles,” noted Jason Havel, city engineer of Iowa City. “It also allows dedicated bike lanes. We can use the pavement markings to diversity the uses of the road.”
Upcoming road diets are planned for First Avenue as part of a project to separate the road from a railroad crossing, and on Mormon Trek Boulevard, which also is getting a right-turn lane to access Benton Street.
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Several more road diets also are under consideration. including on Gilbert, Madison and Clinton streets. Those could be added as soon as next year if the city decides to act, Havel said.
And the cost makes road diets an attractive option.
For example, as part of the work on Mormon Trek and First Avenue, it costs about $30,000 for painting and traffic signal adjustments, Havel said. The cost can jump for road diets requiring traffic signal masts to be moved or erected, Havel said.
The road diet strategy also is on the radar in Cedar Rapids.
Sixth Street SW and First Street near the police station are two opportunities for road diets there, said Matt Myers, Cedar Rapids traffic engineer.
“We are looking at it as well because there’s definite safety advantages — not just for vehicular traffic but for cyclists and pedestrians as well,” Myers said.
Road diets reduce the crossing distance for pedestrians and cyclist because it shrinks the width for vehicle traffic, reduce rear-end collisions and curbs aggressive driving, he added.
Two of the factors Myers looks at to determine if a road diet is a possibility are traffic volumes — 11,000 to 14,000 vehicles per day is the top threshold — and the width of the road, he said.
“If we have four lanes and the traffic volume is low enough, do we have enough curb-to-curb width for bike lanes and three vehicle lanes,” he said.