142nd Street & Douglas Parkway Roundabout Improvements
The City of Urbandale has reconstructed the approaches to the roundabout at Douglas Parkway and 142nd Street. The reconstruction will provide for safer and more efficient roundabout operations.
The City of Urbandale also completed a project along Aurora Avenue this summer, installing a sidewalk connection to Webster Elementary School, which required Aurora Avenue to be closed. The Roundabout project was scheduled after the Aurora Avenue project so as to stagger road closures in the area. Work on roundabout began Monday, August 13, 2018, and was delayed due to frequent rains.
The City of Urbandale appreciated the public's understanding and patience as we completed this project.
Project Status Update - 11/15/18
The entire roundabout is OPEN. Some grading and restoration work remains. While paint striping was done while the roundabout was closed, it did not adhere properly, and paint will be reapplied as temperatures allow in the next few weeks.
Please read below for more information on roundabout operations and the improvements at this intersection.
This project will construct the approaches to better align with the lanes of the Roundabout. This will improve safety by providing a better vehicle path through the intersection, and improve efficiency by maximizing the use of both lanes.
Today's guidelines for Roundabout Design recommend a layout similar to a pinwheel. The current intersection is shaped more like a plus sign. The proposed changes will improve safety and efficiency.
Changes to the approaches will ease the angle of the entry into and exit from the roundabout. This will reduce the risk of broadside collisions, and improve efficiency by aligning the entering vehicles with the roundabout lanes.
Since the Roundabout was constructed in 2004, national standards have been updated. The City of Urbandale has received Traffic Safety Improvement Program (TSIP) funds from the State of Iowa in order to modify the roundabout to comply with current best design standards. The new approaches provide a deflection prior to reaching the roundabout, so that vehicles are aligned with the proper lane when they enter the intersection. There are five ways the new geometry will improve the intersection:
- By placing the vehicle deflection ahead of the roundabout instead of at the yield line, the chance of a broadside collision is reduced.
- The revised approach angle promotes better paths for vehicles to enter and reduces potential path overlap of adjacent vehicle paths.
- Better guidance through the intersection allows motorists to focus more on surrounding traffic and proper lane assignment and less on navigating the roundabout.
- Vehicle speeds will be gently slowed to more consistent speed. Reducing the speed differential makes it easier to find a good gap in circulating traffic to enter the roundabout.
- The above items will make it easier to enter and navigate the roundabout, which in turn reduces wait times and traffic queues for approaching vehicles.
These improvements will result in a safer roundabout, a reduced frequency of crashes, and more efficient vehicle movement through the intersection.
- Visit the Iowa DOT Roundabout Page for more information, including Roundabout Safety and Efficiency and How to Drive a Roundabout.
- Watch Navigating a Multi-Lane Roundabout from the Minnesota Local Roads Research Agency.
Remember, choose your lane at a multi-lane roundabout just as you would at a multi-lane traditional intersection. Yield to vehicles already in the intersection, then proceed through.
Image courtesy of Minnesota Local Roads Research Agency
Image courtesy of Wisconsin DOT