Roundabouts have been widely constructed in states with snowy climates including California (Town of Truckee has several), Colorado, Indiana, Michigan, and Wisconsin. The safety statistics of the roundabouts in these states show consistently positive results, despite the snowy climate.
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Intersection signing must be compliant with the guidelines and standards set forth by the Manual on Uniform Traffic Control Devices (MUTCD). Typical signs that will be installed are roundabout ahead signs, yield signs, pedestrian crossing signs at the crosswalks, guide signs (roadway names) and the one-way signs in the central island. One overhead sign has been evaluated in the environmental document. During the design phase of the project the County will work with Caltrans and the design team to use a combination of roadside signs in place of the overhead signs.
With both alternatives emergency access will be preserved. The traffic analysis indicates the roundabout alternative will reduce overall intersection delay compared to the existing signal, therefore the roundabout is not anticipated to impact emergency response times. The modified signal alternative will increase delay over the existing signal conditions and may impact emergency response, however the implementation of bicycle lanes will allow emergency responders to use the bicycle lane to bypass traffic if needed. Given the current location of the fire station just north of the intersection, the roundabout alternative will improve access for the fire station.
Lighting will be similar to lighting at the existing roundabouts and will be finalized during the design phase.
Adding a bypass lane will significantly increase right of way impacts of the project. Also, a bypass lane configuration also increases risk to pedestrians crossing the street since vehicles are not slowing down to yield at the roundabout. Additionally, the bypass lane would require a raised island to separate traffic and control speeds, which would impact snow removal operations and access to the two parcels on the northeast quadrant of the intersection. The design does provide a right turn lane for westbound SR 28 to minimize queueing and delay and provide acceptable levels of service at the whole intersection.
Traffic analysis shows queuing and delay on SR 267 within acceptable limits. Adding an additional lane to SR 267 would increase environmental and property impacts significantly while providing minimal benefit. The roundabout configuration prioritizes heavy movements to maximize capacity while limiting the number of driver conflicts. Additional lanes through the roundabout would increase the number of conflicts, increase environmental impacts, and increase the cost to build the project.
Curb type has not been selected at this stage of the project and will be done in final design. However, curbs used in the roundabout will need to meet Caltrans Standards and will likely vary based on the application and will be finalized during design. The curb selection type will take into account snow removal operations to minimize the damage sustained to them during snow removal operations.
Most of the damage at the existing roundabouts is likely caused by snowplows. At the proposed roundabout, the circulatory roadway is significantly larger. The larger circulatory roadway will provide more mobility for snow removal operations with less potential to damage the curbs.
The aesthetics for the roundabout will match the aesthetics of the KBCCIP. Sidewalks will be textured and colored, and landscaped areas will match the surrounding natural environment with planting and boulders. Splitter islands entering the roundabout will not have tall planting that will potentially block the drivers’ view of oncoming traffic or pedestrians.