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Thu, Nov. 21

Traffic study prioritizes work needed on Williamson Valley Road
Roundabout possible for intersection at Outer Loop Road

This group of photographs illustrates vision obstruction at Williamson Valley and Outer Loop roads caused by vehicles in the right-turn lane.

This group of photographs illustrates vision obstruction at Williamson Valley and Outer Loop roads caused by vehicles in the right-turn lane.

Based on the final Williamson Valley Road Traffic Study, the Yavapai County Board of Supervisors will prioritize which projects to include in its 2017-18 budget. Several intersections are in need of safety improvements.

Lee Engineering studied 11 miles of the road stretching from Pioneer Parkway to Nancy Drive, looking at 39 cross-street intersections, and reported on existing as well as projected safety and congestion conditions in 2025 and 2040.

Several intersections had sight distance problems relating to visual obstructions such as foliage or embankments, or curvatures (vertical or horizontal) in the roadway.

Drivers on Outer Loop Road at Williamson Valley Road experience a vision obstruction caused by northbound right-turning vehicles, which tend to screen other vehicles heading straight north on Williamson Valley Road.

While existing traffic volumes at Outer Loop Road do not meet conditions, or warrants, for a traffic signal, projected volumes meet warrants at the 70 percent level by 2025. By 2040, it meets 100 percent of warrants.

Roger McCormick, assistant director of Yavapai County Public Works, offered the board this week three options for the Outer Loop Road intersection: turn lanes without a traffic signal, turn lanes with a signal, and a modern roundabout.

Supervisor Jack Smith voiced his dislike of both traffic signals and roundabouts, acknowledging that roundabout designs have improved. Even though the initial cost is greater than traffic signals, from a safety aspect, he prefers roundabouts.

Chair Tom Thurman agreed, saying in the long run, roundabouts pay off.

Study results

The study determined, based on existing Arizona Department of Transportation criteria, that a left-turn lane heading north is needed at Pemberton Drive, as well as a right-turn land heading south. A left-turn lane also is needed at Outer Loop Road.

Northbound left-turn lanes will be needed in 2025: Buena Vista Trail, Rainmaker, Sharps Road, Stazenski Road, and Cielo Grande; a right-turn lane will be needed at Blackjack Ridge Road.

A capacity analysis for traffic congestion rated several stretches of Williamson Valley Road as “D” on an A-F scale with “A” indicating free-flowing traffic and “F” as bumper-to-bumper.

Both northbound afternoon and southbound morning traffic patterns as measured from Pioneer Parkway to Kelly Drive, Kelly Drive to Mendiburo Way, and Mendiburo Way to Glenshandra received a “D” rating. Glenshandra to Outer Loop Road northbound in the afternoon received a “C,” and southbound in the morning received a “D” rating.


The study, which cost $118,207, also looked at crash analysis over the past five years. A total of 115 crashes were reported, with 51 (44 percent) of those involving wildlife. Only five such crashes took place in 2013, the lowest year; 16 occurred in 2015. Half of all crashes on Williamson Valley Road took place in daylight.

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