5 - Gateway Roundabout
A roundabout is a circular intersection with a central island around which traffic must travel counterclockwise and in which entering traffic must yield to circulating traffic. The channelized approaches are delineated with splitter islands on each leg and designed with the appropriate curvature so that travel speeds on the circulator roadway are typically less than 30 miles per hour. Roundabout intersections have fewer and less severe conflict points than tradition intersections.
The study team has identified two potential locations for the installation of roundabouts to replace the existing two of the two-way side-street stop-controlled intersections. The first location is at the Sunset Avenue intersection and the second location is at the Railroad Avenue intersection. If this alternative is selected and either or both of these roundabouts are implemented, then they should be designed in accordance with FHWA design guidelines. US 60 is a delivery route for wind turbine blades and towers, as such the roundabouts should be designed to accommodate such permitted loads. Vehicle turning movements were modeled to determine if these vehicles with wind blades could navigate the roundabout geometry.
The turning movements for a 180-foot wind blade on rear Ackerman Steer capable vehicle are laid out in Appendix B. The accommodation of the wind turbine components results in roundabouts with an inscribed circle diameter of 145-feet. Streetlighting placement for the roundabouts will be crucial to ensure proper illuminance while not interfering with load overhang from the wind turbine blade.
Roundabout at the Sunset Avenue intersection near Mountainair Elementary School (Retained)
The footprint for a roundabout of the size necessary to accommodate wind turbine components overlaps the residential properties in the northeast and southeast quadrants of the intersection. Additionally, the overhang of the wind blade beyond the back axle further extends beyond the roundabout and will require the acquisition of the two residential lots. The parking at Mountainair Elementary School will require some reconfiguration near the roundabout.
Roundabout at the Railroad Avenue intersection (Retained)
Like the Sunset Avenue roundabout, the Railroad Avenue roundabout requires a large footprint. The structure in the northeast quadrant of the intersection would need to be removed in order to accommodate the roundabout.