- This topic has 1 reply, 1 voice, and was last updated 2 years, 1 month ago by
.
-
Posts
-
Thank you to Don Manning for forwarding the following document written by David Stroud, PE, AICP
September 2, 2024
Office of the Mayor and Council
P.O. Box 95050
Henderson, NV 89002Subject: Proposed S-Island at Anthem Parkway/Wild Iris/Solera/Moon Intersection
Please accept this letter as feedback requested by the City of Henderson and Councilman Dan Shaw on the “S-Island”, pictured below as a solution to citizens’ perceived safety concerns. For the following reasons I object to the City’s proposal to implement the S-Island and strongly support that an arterial study with microsimulation be conducted.
- Context
As a retired Professional Engineer (PE), traffic engineer and nationally certified planner (AICP), with 40 years’ experience, a resident of SCA for 5 years, and a regular user of this intersection, I can report the primary movements are left turns out and right turns into and out of Wild Iris Terrace and Solera MoonDrive. Through movements are very minimal. Making left turns from either Wild Iris or Solera Moon Drive onto Anthem Parkway requires driver patience to find an adequate gap in opposing traffic.
The residents of Solera and Sun City Anthem who use the intersection of Anthem
Parkway/Solera Moon Drive/Wild Iris Terrace have been requesting a traffic signal for a dozen years, claiming it is unsafe. In response, the city notes that traffic studies conducted over the years find that a traffic signal is not warranted. The Manual of Uniform Traffic Control Devices (MUTCD) published by the Federal Highway Administration defines the standards used by road managers nationwide to install and maintain traffic control devices on all streets, highways, pedestrian and bicycle facilities, and site roadways open to public travel. According to the MUTCD, there are eight warrants for a traffic signal:Warrant 1, Eight-Hour Vehicular Volume.
Warrant 2, Four-Hour Vehicular Volume.
Warrant 3, Peak Hour.
Warrant 4, Pedestrian Volume.
Warrant 5, School Crossing.
Warrant 6, Coordinated Signal System.
Warrant 7, Crash Experience.
Warrant 8, Roadway Network.No Traffic Signal Needs Studies or supporting data, such as traffic volume turning movement counts, crash data or speed data have been given to the public to review. Therefore, it is not possible to determine what warrants may have been met, if any, or if the City’s traffic engineers are solely using their engineering judgment to decide if a signal is warranted, or both. Nevertheless, the city has determined a traffic signal is not warranted at this intersection. Councilman Shaw states “there is no power at this intersection which creates a lengthy process for the promises of a stoplight”. However, there are streetlights in the Anthem Parkway median, lighted Rectangular Rapid Flashing Beacons (RRFBs) at the
intersection, and a NV Energy transformer within 150 feet of the northwest corner of the intersection.- The Proposed S-Island
The city has proposed an S-Island through the intersection as a response to the residents’ perceived safety concerns.
III. Reasons not to implement the S-Island
A. Intersection Currently Performs Safely
The safety of the intersection based on crash history is not a factor, given the low frequency and lack of severe crashes at this intersection. Thus a traffic signal is not warranted based on crash experience, Warrant 7. Additionally, RRFBs protect pedestrian crossings.
- Elimination of the Desired Left Turns
The elimination of side street left turns and through traffic to remove vehicle conflicts to
improve the safety ironically removes the highly desired left turns. As shown in the picture, the S-Island eliminates side street through traffic and left turns. But the left turns are primarily used to travel to two popular destinations. About 900 resident homes that use Solera Moon Drive would be prohibited from turning left to go the Anthem Highlands Shopping Center (Albertsons). The 480 resident homes in Sun City Anthem on Fox Tail Creek and Hardin Ridge Drive would be prohibited from turning left to go to Sun City Anthem’s Liberty, Independence and Anthem Community Centers.3 C. Unnecessary Excess Travel Distance and Time
The installation of an S-Island converts this four-way intersection that allows all turns into a Restricted Crossing U-Turn (RCUT) intersection by displacing through and left turn movements. The RCUT intersection forces through traffic and left turn traffic from about 480 homes in Sun City Anthem and nearly 900 homes in Solera who use the minor street approaches to turn right and then make a U-turn in the median some distance away from the minor street as depicted below.The displaced left turn and through movements at Solera Moon Drive would now be all right turns. After making the right turn, motorists would weave from the right outside lane to the left inside lane on Anthem Parkway and travel 1,125 feet to make a U-turn at Laurel Heights Lane. Motorists then would travel another 1,125 feet to pass the intersection they just departed, traveling an extra 2,250 feet or just under a half a mile out of their way. Likewise, the displaced left turn and through movements at Wild Iris Terrace would now be all right turns. After making the right turn, motorists would weave from the right outside lane to the left inside lane on Anthem Parkway and travel 3,200 feet to make a U-turn at Schaeffer Hills Drive. Motorists then would travel another 3,200 feet to the intersection they just departed, traveling extra 6,400 feet or nearly 1 ¼ miles out of their way.
- Insufficient Median Width for U-Turn Design and Decreased Safety
The medians on Anthem Parkway are 18 foot wide and at U-turn locations the median is 7 foot wide. Arterials designed for median U-turns typically have a 40 foot wide median because the minimum design radius for a passenger vehicle to make a 180° U-turn is 21.5 feet. Vehicles making a U-turn on Anthem Parkway encroach into the two opposing travel lanes, creating two new vehicle conflict points and raising safety concerns.
The AASHTO Green Book states: “It should be recognized that diverted left-turn volumes may increase congestion and collisions at downstream intersections; provisions to accommodate U-turn traffic should also be considered at downstream locations.” The effects of insufficient median width and weaving can be observed at Schaeffer Hills Drive intersection. This median break is used by Anthem Highland residents making southbound U-turns on Anthem
Parkway to access Dewar Highland St. Gaps in the northbound Anthem Parkway traffic that facilitate the U-turn to Dewar Highland St. are created by the nearby traffic signal at Bicentennial Parkway.- Left Turn Storage Bay Storage Concerns
The increased traffic from the displaced turns at Wild Iris and Solera Moon Drive will make U-turns at Schaeffer Hills Drive and Laurel Heights Lane. The storage length of the existing left turn bays at Schaeffer Hills Drive and Laurel Heights Lane is 220 feet or 11 cars and 115 feet or 6 cars. This storage may be insufficient during peak traffic periods and particularly when a delivery truck is present. If so, vehicles that extend into the inside travel lane will create a safety issue. - Inappropriate Traffic Analysis
Anthem Parkway between Hampton Road and Bicentennial Parkway is an arterial segment nearly 2 miles in length. Between these two signalized intersections there are eleven unsignalized intersections and two driveways with one to the area’s fire station. The intersection of Anthem Parkway with Wild Iris Terrace/Solera Moon Drive is at the beginning/end of a horizontal curve and in the middle of a vertical curve. The vertical curve grade of Anthem Parkway southbound approaching Wild Iris Terrace/Solera Moon Drive is about 3% downhill and the northbound approach grade is about 5% uphill. Residents’ complaints include vehicles operating at speeds higher than the posted 45 mph speed limit.
Given all these considerations and since multiple intersections will be affected by the proposed S-Island, an arterial study should be conducted for this segment of Anthem Parkway which would include a microsimulation analysis (VISSIM) of the arterial. An arterial study with VISSIM microsimulation from Hampton Road to Bicentennial Parkway would provide the city with the full analysis and visual aid needed to answer all residents’ questions about traffic operation on this segment of Anthem Parkway.
- Conclusion
For the forgoing reasons, I object to the city’s proposal to implement the S-Island and strongly support that an arterial study with microsimulation be conducted.
David Stroud, PE, AICP
Having done P&Z as well as adjustments in Florida and being somewhat familiar with the federal highway requirements, Mr. Stroud has done a superior analysis of the situation. This type of analysis would probably cost in today’s dollars a few thousand dollars. The city is getting it for free.
City of Henderson traffic engineering department should pay very strict attention to this analysis. It is excellent!Arthur Goldsmith, Ph.D
- Context
- You must be logged in to reply to this topic.