Flagstaff Ranch Road & Route 66 Intersection Redesign									College of Engineering and Natural Sciences
	Delta Squad III Max Drathman, Joel Tomco, & Kollin Smith
Abstract							Introduction
This project is an intersection redesign of Route 66 at Flagstaff Ranch Road. Due to growth in the surrounding area, the intersection needed to be evaluated and improved. The existing intersection features northbound left and right turn lanes. Route 66 has no turn lanes. For the design, traffic data, existing geometry, and drainage were analyzed. Initially, the addition of a westbound left turn and an eastbound right turn lane were expect to be added, along with extending the northbound left turn lane. Traffic data was collected and analyzed to determine the necessary improvements. Topographical data was attained to examine the existing geometry and to aide in design decisions.								Route 66 is currently a two-way two-lane highway. It has a posted speed of 50 mph and provides service to homes and businesses and connects to I-40. Flagstaff Ranch Road is a two-way two-lane road. It provides service to two housing areas and a few commercial buildings. It has a posted speed of 35 mph. The two roads intersect north of I-40 to form a “T” intersection. The Flagstaff Ranch Subdivision and Aspen Shadows Condos are currently under construction. The housing areas are located next to each other at the end of Flagstaff Ranch Road and are roughly 1 mile south of Route 66. When finished, the volume of the intersection is expected to increase enough to substantiate the redesign of the intersection. The Flagstaff Ranch Subdivision is roughly 20% complete, and the Aspen Shadows Condos are 67% complete. The Flagstaff Ranch Subdivision is also built around a fully operational 18-hole golf course. I-40 runs east/west approximately a half mile south of Route 66. It is expected to handle a large portion of the traffic running from the two housing areas because it is located closer to them than Route 66.
Traffic Analysis
The client, Coconino County Public Works, provided traffic volume counts. This data showed an hourly breakdown of the approach volume; however, it did not display turning movements. To solve this problem, Delta Squad III conducted turning movement counts for the peak AM, PM, and weekend times. The turning movement counts were used to generate a percentage of vehicles turning in any direction. The largest one hour volumes for each direction taken over the course of the volume counts were used as the design volumes. These values were then split based on their respective peak turn percentages. After calculating the volumes for each movement, the data was forecasted 20 years into the future to account for future growth. The increased traffic due to the growth of the subdivision could now be accounted for. Delta Squad III learned the number of currently built homes and the capacity of homes in the subdivisions. The numbers of trips per home were added to the movements departing and arriving at the intersection. The scaled turning movements could now be used to design the geometry of the intersection.
Drainage					Conduit
The drainage at the intersection was analyzed using a USGS topographic map. To the west of the intersection is a natural stream of water that flows south. The stream is at a lower elevation than the intersection, so water west of the intersection will flow to the streambed. The ground elevation heading east of the intersection is decreasing, so water will also flow away from it. There is a small 24” culvert under a driveway on the north side of the intersection. Since all new construction will occur on the south side of Route 66, the culvert on the north side of Route 66 should not be affected. Delta Squad III determined that no new drainage structures would be needed.					Although traffic signals were not warranted, unexpected growth in the near future or after the design year is always a possibility. To ease with potential future construction needs, Delta Squad III designed for conduit under all three approaches. There will be one 3” diameter conduit under each of the listed approaches. They will all connect to ADOT approved pull boxes.
Geometric Design
The geometric design was created according to ADOT and MUTCD standards. The data collected and calculated during the traffic analysis was used to determine if new or existing turn lanes needed to be added or improved.
Westbound Approach		Eastbound Approach							Northbound Approach
The westbound approach calculations suggested the need for a left turn lane with enough storage for 2 vehicles. Delta Squad III accepted this value and designed the turn lane accordingly. A sketch of this approach is presented below.		The eastbound approach calculations suggested the need for a right turn lane with enough storage for 2 vehicles. Delta Squad III used its engineering judgment and decided not to design a right turn lane. The equation that determines the number of vehicles to be stored adds 1 and then rounds that value up to the next integer. The equation for this movement is presented below. nmax^=Maxround(Qsep + 1) From previous calculations, Qsep was found to be 0.02. This value was so minimal, and the geography of the area is so limited to residential expansion, that the decision not to use a right turn lane was justified. A sketch of this approach is presented below.							The northbound approach calculations suggested the need for a left turn lane, but similar to the eastbound approach, the storage value for this lane was small. Since the existing conditions feature a left turn lane, it will be kept in the new design. It will also be lengthened in order to adhere to the ADOT standards for left turn lanes. A sketch of this approach is presented below.
Signs & Striping						Acknowledgements
All pavement striping was designed in accordance with ADOT standards. All striping is thermoplastic. All double yellow striping will be 6” wide and spaced 6” apart. White stripes will be 8” wide. The northbound stop bar will be 18” wide. Thermoplastic strips will be used to display the “ONLY” and arrow markings. Raised reflectors will not be used due to the potential damage from winter snow plows. “T” intersection signs will be placed 500’ before all approaches and they will also denote the cross road being approached. A stop sign will control the northbound approach. Signs designating the northbound turn lanes will be placed at the beginning of the turn lanes.						Client: Coconino County Public Works Client Contact: Dale Wegner, County Engineer, P.E. Technical Advisor: Dr. Ed Smaglik, Ph.D. Dr. Paul Gremillion, Ph. D., P.E. Dr. Joshua Hewes, Ph. D., P.E.
Conclusion
The project began with a 3-way “T” intersection. The traffic counts were analyzed and a new design incorporating a new left turn lane for the westbound approach was established. To counteract the opposing westbound left turn lane, an eastbound no-travel zone was added. Drainage proved not to be an issue, and conduits will be added to accommodate future intersection needs. The new intersection will be safer than the existing and better serve the people of Flagstaff.