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Home My WebLink About02-21 Transportation Technical Memorandum FILENAME: H:\24\24079 - GREYSTONE PROPERTIES LLC REZONING\COMMENTS\24079_MEDIAN ACCELERATION LANE ANALYSIS MEMO.DOCX TECHNICAL MEMORANDUM Greystone Properties, LLC Rezoning Median Acceleration/Storage Lane Analysis Date: December 4, 2020 Project #: 24079 To: Brad Riggleman, P.E. From: Andrew Butsick, P.E.; John Callow Kittelson & Associates, Inc. (Kittelson) developed this memorandum to document the evaluation of a median protected acceleration/storage lane at the proposed access point to the Greystone development on Cedar Creek Grade in Frederick County, Virginia. Attachment A illustrates the proposed lane configuration at the site driveway to be constructed prior to the first occupied dwelling unit within the Greystone development. The intersection was previously evaluated as a traditional two-way stop- controlled intersection as part of the November 2019 traffic impact analysis (TIA), which assumed a site build-out year of 2027. The forecast year 2027 site driveway volumes (post-build out) for the weekday a.m. and weekday p.m. peak hours in the November 2019 TIA were applied to the new proposed lane configuration shown in Attachment A. Table 1 compares the forecast year 2027 post-build out operations under the traditional two-way stop-control intersection (TWSC) and TWSC with the added median acceleration/storage lane. Table 1. 2027 Total Traffic Conditions – Two-Way Stop-Control w/ and w/o Median Acceleration Lane Intersection Information AM Peak Hour PM Peak Hour Intersection (#) Traffic Control Approach Lane Group Existing/ Proposed turn-lane lengths LOS Back of Queue (feet) Delay (sec) LOS Back of Queue (feet) Delay (sec) Route 622 (Cedar Creek Grade)/Site Driveway (#4) Two-way Stop-Controlled EB EBL 200’ A 0 8.0 B 5 11.2 EBT - - 0 0.0 - 0 0.0 EB Approach - - 0.1 - - 0.7 WB WBT - - 0 0.0 - 0 0.0 WBR 150’ - 0 0.0 - 0 0.0 WB Approach - - 0.0 - - 0.0 SB SBL - D 43 32.0 F 65 93.6 SBR - B 5 10.4 C 8 19.3 SB Approach C - 24.4 F - 67.8 Two-Way Stop-Control w/Median Acceleration Lane EB EBL 200’ - 0 0.0 - 0 0.0 EBT - - 0 0.0 - 0 0.0 EB Approach - - 0.0 - - 0.0 WB WBT - - 0 0.0 - 0 0.0 WBR 150’ - 0 0.0 - 0 0.0 WB Approach - - 0.0 - - 0.0 SB SBL - B 10 11.2 C 18 22.5 SBR - B 5 10.4 C 8 19.3 SB Approach B - 10.9 C - 21.4 Greystone Properties, LLC Rezoning Project #: 24079 December 4, 2020 Page 2 Kittelson & Associates, Inc. Reston, Virginia Attachment B contains the Synchro operational worksheets for the intersection with the median acceleration lane. As shown, the addition of a median acceleration/storage lane for southbound left- turning vehicles exiting the site is anticipated to reduce delays from 93.6 seconds (LOS F) to 22.5 seconds (LOS C) during the weekday p.m. peak hour. This reduction in delay results from the ability of southbound left-turning vehicles to complete a two-stage turn, rather than need to find a gap in both eastbound and westbound traffic on Cedar Creek Grade at the same time. As the Highway Capacity Manual, 6th Edition methodologies used to evaluate the median acceleration lane in Synchro do not forecast any delays for the eastbound left-turn movements (due to the required link layout in Synchro to accurately model the median acceleration lane), the operations of the site driveway with the median acceleration lane were also evaluated using SimTraffic software in accordance with VDOT TOSAM parameters. Table 2 illustrates the forecast delays and 95th percentile queues output from the SimTraffic analysis. Attachment C contains the SimTraffic operational worksheets. Table 2. 2027 Total Traffic Conditions – SimTraffic Analysis Intersection Information AM Peak Hour PM Peak Hour Intersection (#) Traffic Control Approach Lane Group Existing/ Proposed turn-lane lengths Delay (sec) Back of Queue (feet) Delay (sec) Back of Queue (feet) Route 622 (Cedar Creek Grade)/Site Driveway (#4) Two-Way Stop-Control w/Median Acceleration Lane EB EBL 200’ 1.9 13 16.7 47 EBT - 0.0 0 0.0 0 WB WBT - 0.5 0 1.4 2 WBR 150’ 0.1 0 0.6 7 SB SBL - 7.0 45 37.0 65 SBR - 4.5 26 18.2 28 As shown, the eastbound left-turn movement is forecast to operate with a total delay per vehicle of 1.9 and 16.7 seconds during the weekday a.m. and weekday p.m. peak hours, respectively. All 95th percentile queues are forecast to be contained within the proposed storage. CONCLUSIONS The proposed site driveway on Cedar Creek Grade is forecast to operate acceptably under year 2027 post-build out traffic conditions with the proposed median acceleration/storage lane. Attachment A Proposed Lane Configurations: Cedar Creek Grade/Site Driveway Attachment B Year 2027 Post-Build Out Traffic Conditions: Synchro Operational Worksheets for Proposed Lane Configuration HCM 6th TWSC Greystone Property 4: Cedar Creek Grade & Greystone Dwy Weekday AM Peak - Total Traffic - Median Acceleration Lane Greystone Property Synchro 10 Report Weekday AM Peak - Total Traffic - Median Acceleration Lane Page 1 Intersection Int Delay, s/veh 2.9 Movement EBL EBT EBR WBL WBT WBR SBL SBR NWL NWR NEL NER Lane Configurations Traffic Vol, veh/h 0 0 0 0 309 26 77 0 0 0 14 0 Future Vol, veh/h 0 0 0 0 309 26 77 0 0 0 14 0 Conflicting Peds, #/hr 0 0 0 0 0 0 0 0 0 0 0 0 Sign Control Stop Stop Stop Free Free Free Stop Stop Stop Stop Free Free RT Channelized - - - - - None - - - - - - Storage Length - - - - - 150 0 200 - - 0 - Veh in Median Storage, # - 0 - - 0 - 0 - 22350 - 22350 - Grade, % - 0 - - 0 - 0 - 0 - 0 - Peak Hour Factor 92 92 92 92 92 92 92 92 92 92 92 92 Heavy Vehicles, % 2 2 2 2 10 0 0 2 2 2 0 2 Mvmt Flow 0 0 0 0 336 28 84 0 0 0 15 0 Major/Minor Major2 Minor2 Conflicting Flow All - - 0 336 336 Stage 1 - - - 336 - Stage 2 - - - 0 - Critical Hdwy - - - 6.4 6.2 Critical Hdwy Stg 1 - - - 5.4 - Critical Hdwy Stg 2 - - - - - Follow-up Hdwy - - - 3.5 3.3 Pot Cap-1 Maneuver 0 - - 663 711 Stage 1 0 - - 728 - Stage 2 0 - - - - Platoon blocked, % - - Mov Cap-1 Maneuver - - - 663 711 Mov Cap-2 Maneuver - - - 663 - Stage 1 - - - 728 - Stage 2 - - - - - Approach WB SB HCM Control Delay, s 0 10.9 HCM LOS B Minor Lane/Major Mvmt WBT WBR SBLn1 SBLn2 Capacity (veh/h) - - 663 711 HCM Lane V/C Ratio - - 0.126 0.064 HCM Control Delay (s) - - 11.2 10.4 HCM Lane LOS - - B B HCM 95th %tile Q(veh) - - 0.4 0.2 HCM 6th TWSC Greystone Property 4: Cedar Creek Grade & Greystone Dwy Weekday PM Peak - Total Traffic - Median Acceleration Lane Greystone Property Synchro 10 Report Weekday PM Peak - Total Traffic - Median Acceleration Lane Page 1 Intersection Int Delay, s/veh 1.3 Movement EBL EBT EBR WBL WBT WBR SBL SBR NWL NWR NEL NER Lane Configurations Traffic Vol, veh/h 0 0 0 0 966 76 45 0 0 0 41 0 Future Vol, veh/h 0 0 0 0 966 76 45 0 0 0 41 0 Conflicting Peds, #/hr 0 0 0 0 0 0 0 0 0 0 0 0 Sign Control Stop Stop Stop Free Free Free Stop Stop Stop Stop Free Free RT Channelized - - - - - None - - - - - - Storage Length - - - - - 150 0 200 - - 0 - Veh in Median Storage, # - 0 - - 0 - 0 - 22350 - 22350 - Grade, % - 0 - - 0 - 0 - 0 - 0 - Peak Hour Factor 92 92 92 92 92 92 92 92 92 92 92 92 Heavy Vehicles, % 2 2 2 2 2 0 0 2 2 2 0 2 Mvmt Flow 0 0 0 0 1050 83 49 0 0 0 45 0 Major/Minor Major2 Minor2 Conflicting Flow All - - 0 1050 1050 Stage 1 - - - 1050 - Stage 2 - - - 0 - Critical Hdwy - - - 6.4 6.2 Critical Hdwy Stg 1 - - - 5.4 - Critical Hdwy Stg 2 - - - - - Follow-up Hdwy - - - 3.5 3.3 Pot Cap-1 Maneuver 0 - - 254 278 Stage 1 0 - - 340 - Stage 2 0 - - - - Platoon blocked, % - - Mov Cap-1 Maneuver - - - 254 278 Mov Cap-2 Maneuver - - - 254 - Stage 1 - - - 340 - Stage 2 - - - - - Approach WB SB HCM Control Delay, s 0 21.4 HCM LOS C Minor Lane/Major Mvmt WBT WBR SBLn1 SBLn2 Capacity (veh/h) - - 254 278 HCM Lane V/C Ratio - - 0.193 0.094 HCM Control Delay (s) - - 22.5 19.3 HCM Lane LOS - - C C HCM 95th %tile Q(veh) - - 0.7 0.3 Attachment C Year 2027 Post-Build Out Traffic Conditions: SimTraffic Operational Worksheets SimTraffic Performance Report Greystone Property Weekday AM Peak - Total Traffic - Median Acceleration LaneWeekday AM Peak - Total Traffic - Median Acceleration Lane Greystone Property SimTraffic Report Weekday AM Peak - Total Traffic - Median Acceleration Lane Page 1 4: Cedar Creek Grade & Greystone Dwy Performance by movement Movement WBT WBR SBL SBR2 NEL All Denied Del/Veh (s) 0.3 3.5 0.2 4.0 0.0 0.8 Total Del/Veh (s) 0.5 0.1 7.0 4.5 1.9 1.9 Queuing and Blocking Report Greystone Property Weekday AM Peak - Total Traffic - Median Acceleration LaneWeekday AM Peak - Total Traffic - Median Acceleration Lane Greystone Property SimTraffic Report Weekday AM Peak - Total Traffic - Median Acceleration Lane Page 2 Intersection: 4: Cedar Creek Grade & Greystone Dwy Movement SB SB NE Directions Served L > L Maximum Queue (ft) 54 32 24 Average Queue (ft) 25 12 2 95th Queue (ft) 45 26 13 Link Distance (ft) 440 98 Upstream Blk Time (%) Queuing Penalty (veh) Storage Bay Dist (ft) 200 Storage Blk Time (%) Queuing Penalty (veh) SimTraffic Performance Report Greystone Property Weekday PM Peak - Total Traffic - Median Acceleration LaneWeekday PM Peak - Total Traffic - Median Acceleration Lane Greystone Property SimTraffic Report Weekday PM Peak - Total Traffic - Median Acceleration Lane Page 1 4: Cedar Creek Grade & Greystone Dwy Performance by movement Movement WBT WBR SBL SBR2 NEL All Denied Del/Veh (s) 1.2 3.1 0.2 4.1 0.0 1.3 Total Del/Veh (s) 1.4 0.6 37.0 18.2 16.7 3.5 Queuing and Blocking Report Greystone Property Weekday PM Peak - Total Traffic - Median Acceleration LaneWeekday PM Peak - Total Traffic - Median Acceleration Lane Greystone Property SimTraffic Report Weekday PM Peak - Total Traffic - Median Acceleration Lane Page 2 Intersection: 4: Cedar Creek Grade & Greystone Dwy Movement WB WB SB SB NE Directions Served T R L > L Maximum Queue (ft) 2 10 79 44 58 Average Queue (ft) 0 1 26 9 19 95th Queue (ft) 2 7 65 28 47 Link Distance (ft) 582 440 98 Upstream Blk Time (%) 0 Queuing Penalty (veh) 0 Storage Bay Dist (ft) 150 200 Storage Blk Time (%) Queuing Penalty (veh)