Compass Homes Development LLC Summit Homes Construction, LLC PO Box 6539 Dillon, CO 80435 Re: Trip Generation Comparison West Hills Townhomes Keystone, Colorado FHU Reference No. 116388-01 Dear Mr. Shutler: Current planning efforts for the Wintergreen Tract A - West Hills Tract at Keystone have identified a potential for affordable (deed restricted) housing. The proposed project site is located along the north side of US 6 to the east of Summit County Road 66; up to 66 townhome units are planned. This particular site within Wintergreen Tract A - West Hills Tract was previously envisioned as an elementary school; the proposed residential uses would displace this previous use. The overall traffic impacts of development within Keystone were addressed in the report entitled Keystone Master Plan Transportation Analysis, Felsburg Holt & Ullevig, June, 1994. This report, now more than 20 years old, included development within Wintergreen Tract A - West Hills Tract (part of Base III, as identified in the Keystone Master Plan). Traffic impacts specific to the previously planned school were not, however, explicitly identified. Therefore, as preliminary evaluation of the relative traffic impacts associated with the proposed change in land use, this letter compares the trip generation potential of the current residential plan to the previously envisioned elementary school. Land Use and Trip Generation As noted above, the current development proposal would allow a maximum of 66 residential townhomes. These units would be affordable (employee) housing and would be deed restricted. The previous concept for this site included an elementary school. Based on typical Summit County elementary schools, an estimated enrollment of 300 students has been used in the following comparative analysis. A trip generation analysis for both current and previous land use plans at Wintergreen Tract A - West Hills Tract was conducted using average weekday data contained in Trip Generation, 9 th Edition, Institute of Transportation Engineers (ITE), 2012, as follows:
Page 2 Affordable Housing. ITE Code 230, Residential Condominium/Townhouse. Per dwelling unit rates applied. 5.81 trips per day, 0.44 trips AM peak hour (17% in, 83% out), 0.52 trips PM peak hour (67% in, 36% out). School. ITE Code 520 Elementary School. Per student rates applied. 1.29 trips per day, 0.45 trips AM peak hour (55% in, 45% out), 0.15 trips PM peak hour (49% in, 51% out). Weekday peak hours of adjacent street traffic has been assumed for both uses. The following table provides a summary comparison between the current and previous plans. Table 1. Trip Generation Comparison Wintergreen Tract A - West Hills Tract Land Use Daily AM Peak Hour PM Peak Hour In Out Total In Out Total Current Development Proposal 66 Affordable Housing Units 383 5 24 29 23 11 34 Previous Development Plan 300 Student Elementary School 387 74 61 135 22 23 45 Change in Trip Generation -4-69 -37-106 +1-12 -11 % Change from Previous Plan -1% -79% -24% As can be seen, the current affordable housing concept would represent a minimal decrease in the daily trip generation of about 4 trips per day (about one percent less than the elementary school). During the critical peak hours, however, there would be a potential for significant reductions. During the AM peak hour, the reduction would be about 106 trips, or 79 percent. During the PM peak hour, the reduction would be about 11 trips, or 24 percent. Auxiliary Lane Evaluation The proposed West Hills Townhomes would take vehicular access via Antler Gulch Road, which then intersects US 6, the primary east-west roadway through the Keystone area. US 6 is a Colorado State Highway. At the intersection with Antler Gulch Road, US 6 consists of a basic fourlane, median-divided cross section. An eastbound left-turn deceleration lane, approximately 440 feet in length (including the taper), is provided within the raised center median. Right-turn acceleration and deceleration lanes are not provided at this intersection. The posted speed limit on US 6 is 45 miles per hour (MPH). To evaluate the potential need for auxiliary lane improvements due traffic associated with the West Hills Townhomes, a preliminary estimate of the existing plus site-generated traffic volumes has been based on year 2040 West Hills Development critical traffic volume projections provided by Summit County (see attached). From these projections, the following estimates are made: Approximately 26 attached residential units currently access via Antler Gulch Road. The trip distribution is approximately 53 percent west/47 percent east.
Page 3 The PM peak hour is critical for inbound movements, which affect deceleration lane requirements. The AM peak hour is critical for outbound movements, which affect acceleration lane requirements. The following table summarizes the resultant components of existing plus site generated traffic to provide a preliminary estimate of the potential impacts of the West Hills Townhomes. Table 2. Critical Volumes for Auxiliary Lane Evaluation US 6 at Antler Gulch Road Critical Period PM Peak Hour AM Peak Hour Movement Estimated West Hills Total Volume Existing Townhomes (vph) Eastbound Left 5 12 17 Westbound Right 4 11 15 Southbound Left 4 11 15 Southbound Right 5 13 18 The above total volumes were then compared to threshold criteria contained in the 1998 State Highway Access Code, Colorado Department of Transportation (CDOT), as amended March 2002 (SHAC). For US 6, the following apply: US 6 between Swan Mountain Road and Gondola Road is classified as an Access Category NR-A, Non-Rural Principal Highway, per the CDOT State Highway Access Category Assignment Schedule, September 2013. The posted speed limit at the Antler Gulch Road intersection is 45 MPH. For category NR-A roads, the following criteria apply, per the SHAC: A left-turn deceleration lane with taper and additional storage length is required for any access with a projected peak hour left ingress turning volume greater than 10 vph. The taper length shall be included within the required deceleration length. A right-turn deceleration lane with taper is required for any access with a projected peak hour right ingress turning volume greater than 25 vph. The taper length shall be included within the required deceleration length. A right-turn acceleration lane is not required on multi-lane highways of this category. Based on the above SHAC criteria, the total projected critical volumes are evaluated as follows: The inbound left-turn critical volume is 17 vph. This exceeds the threshold criteria to require a left-turn lane on eastbound US 6. As previously discussed, the lane currently exists. The inbound right-turn critical volume is 15 vph. This is well below the threshold volume of 25 vph; therefore, a right-turn deceleration lane is not required. US 6 is a multi-lane highway; therefore, a right-turn acceleration lane is not required, regardless of volume.
Yr 2040 Critical Traffic Volumes Auxiliary Turn Lane Requirements per State Highway Access Code Scenario Intersection (vph) Approach vph Ex. Lane (ft) Rquired? Req. (ft) 10 EBL >10 440 Y 625 6 SBL 0 N 22 SBR Accel >50 0 N West Hills Development EBL >10 345 WBR >25 0 SBR Accel >50 0 28 EBL >10 365 Y 460 87 EBR >25 0 Y 435 131 NBL 50 Y per Queue 52 SBR Accel >50 50 Y 550 12 EBL >10 440 Y 625 11 SBL 0 N 26 SBR Accel >50 0 N Wintergreen (36 Apts) Wintergreen (116 Apts) Wintergreen (156 Apts) Wintergreen (196 Apts & Daycare) 4 EBL >10 345 N 15 WBR >25 0 N 9 SBR Accel >50 0 N 29 EBL >10 365 Y 460 89 EBR >25 0 Y 435 140 NBL 50 Y per Queue 53 SBR Accel >50 50 Y 550 15 EBL >10 440 Y 625 16 SBL 0 N 32 SBR Accel >50 0 N 9 EBL >10 345 N 32 WBR >25 0 Y 435 25 SBR Accel >50 0 N 29 EBL >10 365 Y 460 91 EBR >25 0 Y 435 149 NBL 50 Y per Queue 54 SBR Accel >50 50 Y 550 16 EBL >10 440 Y 625 19 SBL 0 N 36 SBR Accel >50 0 N 12 EBL >10 345 Y 460 40 WBR >25 0 Y 435 33 SBR Accel >50 0 N 30 EBL >10 365 Y 460 93 EBR >25 0 Y 435 154 NBL 50 Y per Queue 55 SBR Accel >50 50 Y 550 19 EBL >10 440 Y 625 31 SBL 0 N 44 SBR Accel >50 0 N 18 EBL >10 345 Y 460 64 WBR >25 0 Y 435 54 SBR Accel >50 0 Y 550 31 EBL >10 365 Y 460 96 EBR >25 0 Y 435 168 NBL 50 Y per Queue 57 SBR Accel >50 50 Y 550