What is the Purpose of a Traffic Circle
The purpose of a traffic circle is to reduce the speed of vehicles on residential streets where speeding is occurring. They are not designed to change the volume of traffic on residential streets, and do not significantly reduce cut-through traffic.
How Effective are Traffic Circles
In the City of Tucson, traffic circles have been shown to be very effective in reducing the speed of vehicles traveling on residential streets. Reduction of traffic volume is dependent upon the system of residential traffic management techniques and devices in the area.
From a distance, the traffic circle may appear as an obstruction to traffic. If diverters have been encountered by drivers in other areas of the city, they may turn away from the circle prior to the circle.
How are Trafic Circles Installed in Neighborhoods?
The neighborhood residents/association contacts the Neighborhood Traffic Management Program (NTMP), City of Tucson Traffic Engineering Division at (520) 791-4259 for information.
NTMP will mail a packet that includes the petition forms for the neighborhood residents to sign. 60% of the area residents must approve the project and sign the petition before a study is performed. After a study is completed, a traffic circle could be recommended if speed is a problem.
Design of the Traffic Circle
At the conceptual stage, it is important that the Traffic Advisory Committee understands the neighborhood commitment required for landscaping a traffic circle. If landscaping is incorporated in the mitigation plan, it is essential that the neighborhood is willing to provide the required maintenance.
The neighborhood is required to:
- Provide the plant design
- Obtain the permit
- Install the planting
- Fully maintain the landscaping including:
- Litter control.
Early Planting Consideration
Site conditions play an important part in the feasibility of landscape of the traffic circle. An investigation of the existing site conditions will help to identify potential problems.
The existing underground utilities are the most limiting site condition and must be identified.
Sewer lines, sewer manholes, gas lines and water lines all have the required setbacks. An existing sewer manhole will eliminate the ability to plant trees in the circle.
Sight Visibility and Travel Lane Safety
Safety is a major concern for auto, bicycle, and pedestrian traffic. Sight visibility around the traffic circle must not be blocked with large dense shrubs. Shrubs should be set back accordingly so that mature growth will not extend past the curb edge.
Tree section and setback should be such that the mature tree branches do not extend into the travel lanes below the 14’ level.
Who Pays for the Traffic Circle
The installation of a traffic circle is paid for by the residents themselves. The residents can pay for the traffic circle either through contributions or through the Improvement District. (The Improvement District process can only be used on projects with five or more traffic circles.)
Items to Consdier
- Approved Plant List: The approved plant list can be found in the City of Tucson Development Standard No. 9-06.0.0 in the Engineering Design Section at (520) 791-5100.
- Obtaining a Permit: Any type of digging within the Right of Way (ROW) requires an Excavation Permit; a scaled drawing needs to be submitted to Permits and Codes located at 201 N. Stone Ave ., fourth floor, (520) 791-5100.
- Arizona 811 (Blue Stake): After you obtain your permit, you are ready to call Ar izona 811 to locate under ground
utilities within the project boundary.