by Mari Radtke
Shane Tymkowicz, P.E. is an assistant engineer serving District 3 for Iowa Department of Transportation (IDOT). Tymkowicz presented to the Marcus City Council, the development to date for the construction of a roundabout at the intersection of Highways 143 and 3 south of Marcus on Monday March 11.
Tymkowicz spoke to Council about the benefits of a roundabout, the (current) design and the construction schedule.
The Federal Highway Administration (FHWA) says, “Roundabouts are a proven safety conuntermeasure because they can substantially reduce creashes that result in serious injury or death.” The statement identifies safety improvements by noting they
*Promote lower speeds and traffic calming
*Reduces conflict points
*Leads to imiproved operational performance
*Meet a wide range of traffic conditions because they are versatile in size, shape, and design. IDOT adds vehicle pollution reduction, lower maintenance costs verses traffic signals, increased landscaping opportunities, and pedestrian crossing only one direction of traffic.
Tymkowicz echoed the virtues of a roundabout as he began fielding questions from councilmembers. The current design proposed for construction at the Highway 3 and 143 intersection is, at least partially supported by Kittelson & Associations, a transportaion engineering and planning consulting firm. Specifically, this proposed project is designed for larger vehicles. It features a 180’ outer diameter. It’s outside edges are meant to accommodate a lowboy trailer, often used to deliver extra long loads such as wind turbine blades, farm equipment and other large loads. The roundabout itself is single lane and well lit. Highway approaches from all four directions use the directional cue of splitter islands.
The purchase of 1.1 acres is necessary to complete this project.
Bid letting is currently planned for late 2025. Tymkowicz explained the planned construction schedule in stages; 0 through 5. Current planning begins construction in 2026 with the construction of temporary pavement to avoid the closure of Highway 3.
Stage 1 is access to the Casey’s Convenience Store.
Stage 2 closes L36 south. Cherokee County is responsible for detouring traffic.
Stage 3 is still being refined. That is the Highway 3 build.
Stage 4 brings temporary signals and, while L36 south remains closed, Highway 143 closes.
Stage 5 may force the closure of Highway 3 for safety reasons.
Between now and the final design and letting, IDOT plans to hold public meetings with interested groups and organizations. There are not current plans for pedestrian or bicycle traffic.
The cost of the project belongs to the State of Iowa.
IDOT was also represented Monday evening by Laura Sievers, P.E. and staff engineer. She shared with Council planned upgrades by the State to Highway 143 between Highway 3 and Railroad Avenue. Summer 2024 is when the State will do patchwork on that stretch of road. During the summer of 2025 the same stretch of road will be ground and resurfaced. It will include new rumbles and paves shoulders but no street approaches with the possible exception of Fenton Street.