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Home My WebLink AboutMONTAVA - PHASE G & IRRIGATION POND - BDR210013 - SUBMITTAL DOCUMENTS - ROUND 3 - STREET RELATED DOCUMENT (2) kimley-horn.com 13455 Noel Road, Two Galleria Office Tower, Ste 700, Dallas, TX 75254 (972) 770-1300 July 11, 2022 Max Moss, President HF2M Colorado 430 N College Ave. Suite 410 Fort Collins, CO 80524 Re: Montava Master Planning – Roundabout Design Vehicle Selection, WB-67(MOD) INTRODUCTION In preparing the engineering design for the modern roundabouts planned for the Montava development, the Larimer County Urban Area Street Standards (LCUASS) have been referenced for the applicable design parameters associated with streets, and specifically, roundabouts. Within Appendix I of the LCUASS it is stated that “all roundabouts shall be designed to accommodate the passage of a WB-67 vehicle.” This statement appears to be applicable within the LCUASS for any roundabout regardless of context or connecting roadway classification. This memorandum discusses the validity of an alternate design vehicle within Montava that is based on a WB-67 configuration but is modified to match the largest anticipated vehicle to traverse intersections within Montava based on location, context, and current industry trucking standards. DEFINITION OF A WB-67 A WB-67 design vehicle (Figure 1) has been included within the American Association of State Highway Transportation Officials (AASHTO) library of design vehicles since 2001 (previously referred to as WB- 20). The WB-67 configuration includes a 19.5-foot wheelbase tractor (front axle to center of rear tractor tandem axles), a 53-foot trailer, and a kingpin-to-center-of-rear-tandem (KCRT) axle dimension of 45.5- feet for a total length of 73.5 feet. The “67” in WB-67 comes from the 67-foot distance from the center of the front axle to the center of the rear axle. Nearly two dozen states in the U.S. limit the KCRT dimension to 40ft or 41ft, therefore, the WB-67 is not a nationwide standard. WB-67s have been the typical assigned design vehicle for interstate transport and roadways within heavy industrial zones within the states where KCRT dimensions above 41ft are permitted. A map of the allowable wheelbase dimensions above and below the 40ft-41ft length is included in Figure 2. Figure 1 - WB-67 Design Vehicle (AASHTO 2018) kimley-horn.com 13455 Noel Road, Two Galleria Office Tower, Ste 700, Dallas, TX 75254 (972) 770-1300 Figure 2 - KCRT Allowances Across the U.S. Image Source: https://www.bigtruckguide.com/kingpin-to-rear-axle/ URBAN AND SUBURBAN DESIGN VEHICLE SELECTION Based on our experience participating in the design of thousands of intersections across 40+ states in the U.S., the WB-62 design vehicle (Figure 3) has become a common largest anticipated vehicle within urban and suburban locations for arterial roadways. The WB-62 most closely resembles the turning maneuver for the large trucks on urban arterials due to its 40.5-foot wheelbase. One parameter the WB-62 may not as accurately account for is the front and rear overhang of a 53-foot trailer since the WB-62 is modeled with a 48-foot trailer. The difference in vehicle envelope with a 48-foot trailer versus a 53-foot trailer is very minor, and therefore, the WB-62 becomes the frequent chosen design vehicle within the urban and suburban context due to its highly similar turning maneuver and subsequent wheel path to that of a 53-foot trailer with a modified wheelbase of 41-feet. A WB-50 design vehicle is another alternative vehicle used by many local public agencies, although AASHTO no longer recognizes it within their vehicle library. Figure 3 - WB-62 Design Vehicle (AASHTO 2018) kimley-horn.com 13455 Noel Road, Two Galleria Office Tower, Ste 700, Dallas, TX 75254 (972) 770-1300 REVIEW OF A WB-67(MOD) AS THE MONTAVA ROUNDABOUT DESIGN VEHICLE A blended approach towards the selection of the proper design vehicle for Montava is the consideration of a 53-foot trailer with the modified wheelbase of a WB-62 (41-foot wheelbase). This type of vehicle is the preferred design vehicle in other states in the U.S. – known as a WB-67SR in Georgia. While the WB- 67(MOD) would still be considered more conservative than the largest anticipated vehicle within Montava, it would align with the LCUASS in preparing roundabout geometry that accommodates a 53-foot trailer. On June 9, 2022 a site audit near the Anheuser-Busch facility located at 3823 Mountain Vista Dr adjacent to I-25 resulted in observations of trucks adjacent to the facility shown in the photos in Figure 4. While 53-foot trailers were prevalent at the site, it was noted that all trucks hauling 53-foot trailers had the rear tandem axles pulled forward. In some cases, the wheelbases had been modified well below the 41-foot value to a 34-foot KCRT dimension. Undoubtedly, Montava will see 48-foot construction trailers as the site develops for larger equipment and materials delivery. Based on the adjacent roadway network, however, 53-foot trailers are not anticipated within Montava except for N Giddings Road (Figure 5). With most semitrailers being banned from Country Club Road between Turnberry and Highway 1 by Larimer County in 2020, this area is not anticipated to generate large truck traffic. One exception within the Montava site could be moving trucks that employ 53-foot trailers (i.e. Mayflower, Allied Van Lines). In discussions with Mayflower representatives in June 2022 it was noted that the Mayflower residential moving trucks that haul 53-foot trailers make use of a fixed 38-foot KCRT, slightly shorter than the WB-67SR shown in Figure 6. kimley-horn.com 13455 Noel Road, Two Galleria Office Tower, Ste 700, Dallas, TX 75254 (972) 770-1300 Figure 4 – Truck Audit Near the Anheuser-Busch Facility on June 9, 2022 kimley-horn.com 13455 Noel Road, Two Galleria Office Tower, Ste 700, Dallas, TX 75254 (972) 770-1300 Figure 5 – Adjacent Roadway Network to Montava, Image Source: montava.com kimley-horn.com 13455 Noel Road, Two Galleria Office Tower, Ste 700, Dallas, TX 75254 (972) 770-1300 Figure 6 - Various 53-foot Trailer Configurations RECOMMENDATION Due to the potential for moving trucks to access Montava post-construction, it is our recommendation that a WB-67(MOD), or WB-67SR (Figure 6), design vehicle be considered as the largest anticipated vehicle within the Montava development. A WB-67 design vehicle, as prescribed within the LCUASS, is uniquely suited for cross-country interstate travel within the states that allow above a 41-foot KCRT. However, a WB-67 would not be anticipated to route within the Montava development for any type of use or function. The use of a 53-foot trailer on a modified 41-foot wheelbase (WB-67SR) is the current industry standard for large trucks accessing this type of context and is a reasonable and feasible design vehicle for a conservative approach towards roundabout geometrics in Montava. Attachments: Appendix A – Nearby Local Public Agency Design Vehicle Standards Appendix A Montava Nearby Local Public Agency Design Vehicle Standards COLORADO SPRINGS Appendix A Montava Nearby Local Public Agency Design Vehicle Standards COLORADO SPRINGS Appendix A Montava Nearby Local Public Agency Design Vehicle Standards BOULDER Appendix A Montava Nearby Local Public Agency Design Vehicle Standards BRECKENRIDGE Appendix A Montava Nearby Local Public Agency Design Vehicle Standards DENVER Appendix A Montava Nearby Local Public Agency Design Vehicle Standards El PASO COUNTY Appendix A Montava Nearby Local Public Agency Design Vehicle Standards El PASO COUNTY Appendix A Montava Nearby Local Public Agency Design Vehicle Standards GILPIN COUNTY