SR 174/20 Intersection
SR 174/20 Roundabout and Active Transportation Safety Project
As part of the regional transportation planning process, the Nevada County Transportation Commission (NCTC) has been coordinating efforts with the City of Grass Valley, Caltrans and a transportation consulting firm, GHD, to perform a complete Intersection Control Evaluation (ICE) for the intersection of South Auburn Street, State Routes 174 and 20, Neal Street, and frontage roads Tinloy Street and Hansen Way (The “Triangle”). The Triangle has seen little improvement since its construction in the late 1960’s, while traffic levels have grown dramatically. The complicated layout of three closely spaced signalized intersections leads to unnecessary delays and unsafe movements, as well as severely outdated pedestrian and bicycle facilities. An ICE is a Caltrans specified process that analyzes the entire project location to determine optimum traffic control treatments and intersection geometry based on an objective analysis considering technical, financial, environmental, aesthetic and safety concerns for the existing conditions and future needs.
Following a lengthy analysis and development process, GHD completed the recommended improvement plan in 2022. The SR 174/20 Roundabout and Active Transportation Safety Project is intended to improve traffic operations and the safety and comfort for people walking and bicycling by simplifying a high-stress cluster of multiple intersections with an oblong single-lane roundabout that includes high-visibility crossings on all legs and a shared-use path. The project area today consists of seven closely spaced intersections, known as the Triangle, at the interchange of SR 174 with SR 49/20. Intersections are a mix of traffic signals and side-street stop signs, and people bicycling or walking through the area must navigate multiple long crossings with varied markings and support features.
A new oblong roundabout will consolidate four intersections, offering safety improvements for all modes of transportation. High-visibility marked crosswalks will be provided on all approaches, including advance yield lines and refuge islands. A rectangular rapid flashing beacon (RRFB) will be installed across S. Auburn Street near Grass Valley Charter Elementary. Two marked crossings are also provided across the circulating lane to provide access to the Park and Ride lot, and will include RRFBs to support safe crossings for students and families to Grass Valley Charter Elementary. A new shared-use path will be constructed around the roundabout, offering a safe path of travel for people walking and bicycling that is completely separated from motor vehicle traffic. An existing traffic signal at Neal Street and Auburn Street will be upgraded to improve pedestrian safety and coordinate with the adjacent roundabout.
