The intersection of Williams Boulevard and Dean Road SW has a history of crashes resulting in serious injury. Following an analysis of the crash rates, traffic volumes, and vehicle speeds, the City of Cedar Rapids is constructing a roundabout at the intersection of Williams Boulevard and Dean Road in the summer of 2020. Roundabouts have been shown to significantly reduce speeds and reduce, or eliminate, the number and severity of crashes.
Renderings: Commuter Traffic
Renderings: Neighborhood Specific
We wanted to provide residents off Dean Road with resources to help transition to using the roundabout. Below are renderings with information and directional guidance for using the roundabout to either leave your neighborhood or return to your neighborhood
- Mid-March 2020 // construction of temporary access road // lane reductions in effect
- April 2020 // construction of roundabout // full closure in effect
- August - Fall 2020 // project completed
Center Island Design
The roundabout's design includes a center island with a berm (mound) and landscaping in the middle, which is intentional and a component of almost all modern roundabouts.
The berm in the center island serves multiple purposes:
- The mounded berm helps increase the visibility of the intersection
- The berm promotes lower speeds by decreasing excessive sight distance
- The berm helps break up headlight glare of oncoming vehicles at night
When motorists are approaching the roundabout they should first yield to pedestrians before looking to their left and merging when safe. A center island berm keeps the focus on vehicles coming from the left, which is where drivers should be looking when approaching a roundabout. The maximum speed that vehicles can comfortably drive through a roundabout is between 20 to 25 MPH, which provides adequate time to judge an appropriate gap in traffic immediately to your left.
Why Choose a Roundabout?
- Eliminates most severe crash types
- Forces vehicles to slow down
- No signal delays; better traffic operations
- Can handle high traffic volumes during rush hour
- Can accommodate trucks
- Average speeds: 60 mph
- Average traffic volumes: 18,000 vehicles per day
- 24 crashes in the last 5 years:
11 Property Damage
Challenges of Traffic Signals at this Location
- Signals do not eliminate severe head-on/right-angle crashes
- Signals can still result in serious injury on high-speed roadways
- Signal back-ups can occur during peak travel times
Download a brochure from the Federal Highway Administration on the benefits of using roundabouts on rural highways:
View material used during a neighborhood meeting held on February 28, 2019
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Frequently Asked Questions (updated 2/14/2020)
Q: What are the goals of the project?
A: The primary purpose of the project is to improve safety and reduce the number and severity of crashes. Roundabouts have been shown to significantly reduce crashes, even on rural highways. They are the best solution for reducing speeds, eliminating the risk of motorists misjudging gaps, and eliminating head-on and right-angle crashes. A roundabout is also efficient at handling high volumes of traffic and can support future development along Highway 151.
Q: What is the overall project timeline?
A: The project would be bid and awarded to a contractor in winter 2020, with construction spring/summer 2020.
Q: What is the cost of the project?
A: The project is estimated to cost approximately $1.6 million. The City of Cedar Rapids has secured $900,000 in safety grants from the Iowa Department of Transportation and Linn County.
Q: Has the City considered a traffic signal at this location?
A: The City conducted an engineering analysis and determined that a roundabout is the best solution for this location, due to its safety and operational benefits. One of the primary reasons we did not pursue a signal is because the installation of a traffic signal would not reduce the number and severity of crashes. Increasing the number of signals per mile of roadway causes the number of crashes (and the crash rate) to increase.
Q: Will large vehicles (fire, ambulance, school bus) be able to go through the roundabout?
A: Yes, this roundabout is designed to accommodate the largest vehicle allowed by law on the highway. This includes tractor-trailer combination (semi-truck), firetruck, school bus, combine, etc.
Q: What considerations have been given to the Stoney Point Road intersection, and the interchange with US HWY 30?
A: While we are working to meet an immediate need at Williams and Dean, we are also aware of other corridor needs. We have been continually monitoring the traffic signal at Stoney Point Road, have updated the signal timings to reduce the line of cars “queuing,” and will be installing advance warning signage. We also ensured that resident concerns we received at the public meeting held on February 28 were shared directly with the Iowa Department of Transportation and Linn County.
Q: Would reducing the speed limit and posting new speed limit signage help reduce speeds?
A: Studies have consistently shown that speed limit signage is not a significant enough deterrent to reduce speeding. Highway 151 will remain a high-speed arterial unless the physical environment changes and compels drivers to slow down. Additional information regarding speed limits can be found on the DOT’s website: https://www.iowadot.gov/traffic/manuals/pdf/speedlimitbrochure.pdf.
Q: Will residents be able to access their homes during construction?
A: Yes. Property owners will have access to their homes during construction. Property owners will receive more detailed information regarding their access points and detours when we get closer to construction.
Q: Where can residents find more information on how to drive roundabouts?
A: There are a number of good resources available to help drivers become more familiar with driving roundabouts.
- City of Cedar Rapids: www.cityofcr.com/roundabouts.
- Federal Highway Administration: https://safety.fhwa.dot.gov/intersection/innovative/roundabouts/
- Insurance Institute for Highway Safety: https://www.iihs.org/iihs/topics/t/roundabouts/topicoverview
- Iowa Department of Transportation: https://iowadot.gov/traffic/roundabouts
- Iowa State University's Center for Transportation Research and Education: https://ctre.iastate.edu/research-synthesis/rural-speed-management/horizontal-displacement/roundabouts-2/
In addition to these resources, the City offers “ride-alongs” to give residents an opportunity to drive a roundabout with an engineer and grow more comfortable with how it operates, prior to any roundabout opening in their neighborhood.