College of Engineering Unit:
The main goals of the Old Bend Redmond Intersection improvement project are to redesign the intersection to be able to handle the predicted influx of traffic flow over the coming years and improve public safety at the intersection of US20 and Old Bend Redmond Highway. Issues with the current design include deteriorating pavement, long queuing times, large vehicle mobility issues, and significant crash history.
The final design created to fix traffic issues is a two lane roundabout with a 175 foot inscribed diameter, 14-16 foot wide lanes, a red and textured 10 foot truck apron with a 1% cross-slope, and dedicated right turn lanes off of US 20. All details conform to the Oregon Department of Transportation highway design manual including standard low profile mountable curbs and a 2% cross-slope of the circulatory roadway.
In order to improve safety and accessibility all ADA requirements have been fulfilled using standard drawings. The design of the crosswalks will align with the curb ramps found at the edge of the sidewalk and be located 25 feet in advance of the yield line with 8’ x 1’ markings delineating the area. Raised Medians were added to ensure the safety of pedestrians when using the crosswalks. Dark-sky compliant street lights will be added in order to conform to the City of Bends light pollution requirements. These streetlights will be 25 feet in height and spaced 75 feet apart.
In order to accommodate for water runoff 4 ditches have been placed on each side of the roundabout. Each ditch was designed to the worst-case scenario of a runoff volume of 1400 cubic feet. A trapezoidal shape was utilized with a total width of 7 feet, bottom width of 5 feet, depth of 2 feet, and a wall angle of 63.4 degrees from base.
With this design, the project goals of reduced queues, increased safety, and increased truck maneuverability have been achieved. Queuing will no longer be an issue indicated by a level of service that has been promoted to an A rating for all legs. Roundabouts inherently improve safety by slowing traffic and decreasing the need to cross lanes. Trucks will be able to maneuver the intersection safely with dedicated turn lanes giving the option to skip the roundabout, a conservatively designed truck apron to ride up on, and a diameter that conforms to their size.
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