Traffic Impact Study for the Grove Street Subdivision

Transcription

1 Whitlock & Weinberger Transportation, Inc. 490 Mendocino Avenue Suite 201 Santa Rosa, CA voice (707) fax (707) th Street Suite 290 Oakland, CA voice (510) website Traffic Impact Study for the Grove Street Subdivision in the Draft Report August 15, 2014

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3 Table of Contents Executive Summary... 1 Introduction... 2 Transportation Setting... 4 Capacity Analysis... 7 Alternative Modes...15 Access and Circulation...16 Conclusions and Recommendations...18 Study Participants and References...19 Figures Tables 1 Lane Configurations and Existing Traffic Volumes Cumulative and Project Traffic Volumes Site Plan Farmstand Mini-Roundabout Concept Bicycle Facility Summary Intersection Level of Service Criteria Existing Peak Hour Intersection Levels of Service Cumulative PM Peak Hour Levels of Service Trip Generation Summary Trip Distribution Assumptions Existing and Existing plus Project Peak Hour Intersection Levels of Service Cumulative and Cumulative plus Project PM Peak Hour Levels of Service Appendices A Intersection Level of Service Calculations B Proportional Share Calculations C Roundabout Calculations Page Traffic Impact Study for the Grove Street Subdivision in the August 15, 2014 Page i

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5 Executive Summary The proposed project would allow subdivision of two existing lots to create 30 separate parcels, which were assumed to be developed with 23 for single family homes and seven with the Grove Street Mixed Use (GMU) designation. Single family dwellings were assumed for each of the 30 lots, with commercial uses varying from small offices to retail spaces also included on the mixed use lots. A total of 12,000 square feet of commercial use was assumed for the entire subdivision. Access to the subdivision would be via a new street intersection on Grove Street, which is proposed as a mini-roundabout. The proposed subdivision is expected to generate an average of 818 trips daily, including 35 during the morning peak hour and 63 during the evening peak hour. All of these trips were assumed to be new trips though some associated with the commercial uses may be drawn from passing traffic. To provide a more conservative assessment, these pass-by trips were not deducted. Four intersections were evaluated in the traffic study, including Dry Creek Road at the US 101 South and North ramps as well as Grove Street and Grove Street at West Grant Street. All of these intersections are currently operating acceptably at LOS C or better overall, and will continue to do so upon adding project-generated traffic. It is noted that the southbound off-ramp operates at LOS E or F; however, under the Caltrans standards applied this is not significant. The City s General Plan calls for signalization of the interchange, and with signalization the ramp intersections are expected to operate acceptably at LOS D or better under future volumes without and with the project. The project should contribute a proportional share towards this planned future project. The proposed mini-roundabout provides numerous benefits, in addition to accommodating ingress to and egress from the project site. It also has traffic calming effects, which is desirable given ongoing concerns about the speed of traffic along Grove Street through this long, straight stretch between intersections. Further, it provides a low-speed environment conducive to pedestrian crossings, with splitter islands between lanes that can be used by pedestrians to wait briefly for a gap in traffic without being in the opposing path of travel. Finally, it is more aesthetically pleasing than the most likely alternative for creating a break in traffic of all-way stop controls, which have the further environmental impact of creating additional greenhouse gases associated with all vehicles needing to stop. The project will provide sidewalk along its frontage as well as crossings of Grove Street at the proposed mini-roundabout, effectively tying the site to the existing path on the east side of Grove Street and resulting in adequate pedestrian access. Bicyclists can use the path on the east side of the street or travel in the street, depending upon their skill level. As part of the frontage improvements signing should be installed indicating that southbound Grove Street is a Class III bike route. Additionally, bike parking should be provided for any commercial uses ultimately developed on the Mixed Use parcels. Traffic Impact Study for the Grove Street Subdivision in the August 15, 2014 Page 1

6 Introduction Introduction This report presents an analysis of the potential traffic impacts that would be associated with development of a proposed residential and commercial project to be located on the west side of Grove Street in the. The traffic study was completed in accordance with the criteria established by the, and is consistent with standard traffic engineering techniques. Prelude The purpose of a traffic impact study is to provide City staff and policy makers with data that they can use to make an informed decision regarding the potential traffic impacts of a proposed project, and any associated improvements that would be required in order to mitigate these impacts to a level of insignificance as defined by the City s General Plan or other policies. Vehicular traffic impacts are typically evaluated by determining the number of new trips that the proposed use would be expected to generate, distributing these trips to the surrounding street system based on existing travel patterns or anticipated travel patterns specific to the proposed project, then analyzing the impact the new traffic would be expected to have on critical intersections or roadway segments. Impacts relative to access for pedestrians, bicyclists, and to transit are also addressed. Project Profile The proposed project consists of the subdivision of two existing lots to create 30 separate parcels. These 30 lots will include 23 for single family homes; the remaining seven would have the Grove Street Mixed Use (GMU) designation. It was assumed that there would be single family dwellings on each of the 30 lots, with commercial use also developed on the mixed use lots. The sizes of the commercial developments would likely vary from small office uses to retail spaces. A total of 12,000 square feet of commercial use was assumed for the entire subdivision. Access to the subdivision would be via a new street intersection on Grove Street, which is proposed as a mini-roundabout. The project site is located on the west side of Grove Street, as shown in Figure 1. Traffic Impact Study for the Grove Street Subdivision in the August 15, 2014 Page 2

7 Grove Street 1 US 101 SB Ramps Dry Creek Road Dry Creek Rd 7 (25) 2 (2) 132(104) (200)111 (170) (214) 359(436) 2 US 101 NB Ramps 2 Project Site Dry Creek Rd (12) 10 (296)230 (71)107 (438) (266) 455(572) Grove St 3 148(125) 64 (66) 21 (20) 43 (24) 434(578) 60 (86) Dry Creek Rd (92)111 (469)497 (105)111 (122)83 (62)42 (116) (9) 151(202) 44 (65) 35 (60) 7 (7) 107(133) 4 Grant Street Grove St Grant St (3)1 (7)6 (8)4 (10) 2 (196)108 (127) 61 North Not to Scale Traffic Impact Study for the Grove Street Subdivision Figure 1 Lane Configurations and Existing Traffic Volumes LEGEND Study Intersection xx A.M. Peak Hour Volume (xx) P.M. Peak Hour Volume Counts Taken July 2014 at Intersections 1,2 and April 2014 Intersections 3,4 060hea.ai 7/14

8 Transportation Setting Operational Analysis Study Area and Periods The study area consists of the following intersections: 1. US 101 Northbound off-ramp/dry Creek Road 2. US 101 Southbound off-ramp/dry Creek Road 3. Grove Street/Dry Creek Road 4. Grove Street/West Grant Street Operating conditions during the a.m. and p.m. peak periods were evaluated to capture the highest potential impacts for the proposed project as well as the highest volumes on the local transportation network. The morning peak hour occurs between 7:00 and 9:00 a.m. and reflects conditions during the home to work or school commute, while the p.m. peak hour occurs between 4:00 and 6:00 p.m. and typically reflects the highest level of congestion during the homeward bound commute. Study Intersections US 101 Northbound off-ramp/dry Creek Road is an unsignalized intersection with a stop sign on the south leg for the Northbound off-ramp. The north leg is a one-way on-ramp. There are no crosswalks. US 101 Southbound off-ramp/dry Creek Road is an unsignalized intersection with a stop sign on the north leg for the Southbound off-ramp. The south leg is a one-way on-ramp. There are no crosswalks Grove Street/Dry Creek Road is a signalized intersection with protected left turns on the east and west legs. There are crosswalks on all legs of the crosswalk. Grove Street/West Grant Street is a four-way stop controlled intersections with two lanes in each direction. Crosswalks are provided on the south and east legs of the intersection. The locations of the study intersections and the existing lane configurations and controls are shown in Figure 1. Study Roadways Grove Street is a north-south street with one lane in either direction measuring approximately 12 feet in width each. The posted speed limit on Grove Street is 30 miles per hour (30 mph). Dry Creek Road is an east-west arterial road with one to two lanes in each direction. The posted speed limit is 30 miles per hour (mph). West Grant Street is an east-west road with one lane in either direction, each measuring approximately eleven feet in width. There is no posted speed limit, but because it is a residential street the prima facia is 25 miles per hour (mph). Traffic Impact Study for the Grove Street Subdivision in the August 15, 2014 Page 4

9 Alternative Modes Pedestrian Facilities Pedestrian facilities include sidewalks, crosswalks, pedestrian signal phases, curb ramps, curb extensions, and various streetscape amenities such as lighting, benches, etc. In general, the network of sidewalks in the vicinity of the proposed project site is discontinuous; sidewalk gaps, obstacles, and barriers can be found along all of the roadways connecting to the project site. Existing gaps and obstacles along the connecting roadways impact convenient and continuous access for pedestrians and present safety concerns in those locations where appropriate pedestrian infrastructure would address potential conflict points. Grove Street Intermittent sidewalk coverage is provided on Grove Street with significant gaps on both sides of the street between Dry Creek Road and West Grant Street. West Grant Street Continuous sidewalks are provided on both sides of West Grant Street from Grove Street to the east. Sidewalks are not provided on the south side of the street from Grove Street towards the west. Street lights are provided along this road. Dry Creek Road Intermediate sidewalk coverage is provided on Dry Creek Road with significant gaps on the north side of the street. Bicycle Facilities The Highway Design Manual, California Department of Transportation (Caltrans), 2012, classifies bikeways into three categories: Class I Multi-Use Path: a completely separated right-of-way for the exclusive use of bicycles and pedestrians with cross flows of motorized traffic minimized. Class II Bike Lane: a striped and signed lane for one-way bike travel on a street or highway. Class III Bike Route: signing only for shared use with motor vehicles within the same travel lane on a street or highway. In the project area, there is a Class I pathway to the south and adjacent to Grove Street, Class II bike lanes on Grove Street to the north, and Class III bike routes on Dry Creek Road and March Avenue. Future plans will extend the Foss Creek Pathway from the northerly City Limits to Front Street on the south, near the future SMART station. March Avenue is expected to be striped with Class II bike lanes in the near future. Bicyclists ride in the roadway and/or on sidewalks along all other streets within the project study area. Table 1 summarizes the existing and planned bicycle facilities in the project vicinity, as contained in the Healdsburg Bicycle & Pedestrian Master Plan. Traffic Impact Study for the Grove Street Subdivision in the August 15, 2014 Page 5

10 Status Roadway Existing Class Table 1 Bicycle Facility Summary Length (miles) Begin Point End Point Foss Creek Pathway I 0.25 Mill St South of Foss Creek Cir Grove Street II 0.57 Healdsburg Ave North of Dry Creek Rd Dry Creek Rd III 0.17 Grove St Healdsburg Ave March Avenue III 0.48 Healdsburg Ave University St Planned Foss Creek Pathway I 3.6 City Limits North Front Street March Avenue II 0.48 Healdsburg Ave University St Grove St III 0.94 Dry Creek Rd Foss Creek Pathway Source: Healdsburg Bicycle & Pedestrian Master Plan, adopted October 20, 2008 Traffic Impact Study for the Grove Street Subdivision in the August 15, 2014 Page 6

11 Intersection Level of Service Methodologies Capacity Analysis Level of Service (LOS) is used to rank traffic operation on various types of facilities based on traffic volumes and roadway capacity using a series of letter designations ranging from A to F. Generally, Level of Service A represents free flow conditions and Level of Service F represents forced flow or breakdown conditions. A unit of measure that indicates a level of delay generally accompanies the LOS designation. The study intersections were analyzed using methodologies published in the Highway Capacity Manual (HCM), Transportation Research Board, This source contains methodologies for various types of intersection control, all of which are related to a measurement of delay in average number of seconds per vehicle. The Levels of Service for the interchange intersections, which have side-street stop controls, or are unsignalized and have one approach stop-controlled, were analyzed using the Two-Way Stop- Controlled intersection capacity method from the HCM. This methodology determines a level of service for each minor turning movement by estimating the level of average delay in seconds per vehicle. Results are presented for individual movements together with the weighted overall average delay for the intersection. The intersection of Grove Street/Grant Street has stop signs on all approaches and was analyzed using the All-Way Stop-Controlled Intersection methodology from the HCM. This methodology evaluates delay for each approach based on turning movements, opposing and conflicting traffic volumes, and the number of lanes. Average vehicle delay is computed for the intersection as a whole, and is then related to a Level of Service. The study intersections that are currently controlled by a traffic signal, like Dry Creek Road/Grove Street, or may be in the future, like the interchange intersections, were evaluated using the signalized methodology from the HCM. This methodology is based on factors including traffic volumes, green time for each movement, phasing, whether or not the signals are coordinated, truck traffic, and pedestrian activity. Average stopped delay per vehicle in seconds is used as the basis for evaluation in this LOS methodology. For purposes of this study, delays were calculated using optimized signal timing. The ranges of delay associated with the various levels of service are indicated in Table 2. Traffic Impact Study for the Grove Street Subdivision in the August 15, 2014 Page 7

12 Table 2 Intersection Level of Service Criteria LOS Two-Way Stop-Controlled All-Way Stop-Controlled Signalized A Delay of 0 to 10 seconds. Gaps in traffic are readily available for drivers exiting the minor street. B Delay of 10 to 15 seconds. Gaps in traffic are somewhat less readily available than with LOS A, but no queuing occurs on the minor street. C Delay of 15 to 25 seconds. Acceptable gaps in traffic are less frequent, and drivers may approach while another vehicle is already waiting to exit the side street. D E F Delay of 25 to 35 seconds. There are fewer acceptable gaps in traffic, and drivers may enter a queue of one or two vehicles on the side street. Delay of 35 to 50 seconds. Few acceptable gaps in traffic are available, and longer queues may form on the side street. Delay of more than 50 seconds. Drivers may wait for long periods before there is an acceptable gap in traffic for exiting the side streets, creating long queues. Delay of 0 to 10 seconds. Upon stopping, drivers are immediately able to proceed. Delay of 10 to 15 seconds. Drivers may wait for one or two vehicles to clear the intersection before proceeding from a stop. Delay of 15 to 25 seconds. Drivers will enter a queue of one or two vehicles on the same approach, and wait for vehicle to clear from one or more approaches prior to entering the intersection. Delay of 25 to 35 seconds. Queues of more than two vehicles are encountered on one or more approaches. Delay of 35 to 50 seconds. Longer queues are encountered on more than one approach to the intersection. Delay of more than 50 seconds. Drivers enter long queues on all approaches. Reference: Highway Capacity Manual, Transportation Research Board, 2000 Traffic Operation Standards Delay of 0 to 10 seconds. Most vehicles arrive during the green phase, so do not stop at all. Delay of 10 to 20 seconds. More vehicles stop than with LOS A, but many drivers still do not have to stop. Delay of 20 to 35 seconds. The number of vehicles stopping is significant, although many still pass through without stopping. Delay of 35 to 55 seconds. The influence of congestion is noticeable, and most vehicles have to stop. Delay of 55 to 80 seconds. Most, if not all, vehicles must stop and drivers consider the delay excessive. Delay of more than 80 seconds. Vehicles may wait through more than one cycle to clear the intersection. The intersection Level of Service (LOS) standard for Healdsburg is contained in the Healdsburg 2030 General Plan Policy Document, and reads as follows: The City shall strive to maintain Level of Service D operation during periods of peak traffic flow at critical intersections, and Level of Service C operation at all other times. These standards shall apply only to intersections of an arterial street with either another arterial or a collector street and intersections of two collector streets. Further, LOS F operation shall be acceptable for a stopcontrolled approach to a through street provided the higher levels of delay affect 25 vehicles per hour or less. Attainment of these Levels of Service shall be consistent with the financial resources available and the limits of technical feasibility. Existing Conditions The Existing Conditions scenario provides an evaluation of current operation based on existing traffic volumes during the a.m. and p.m. peak periods. This condition does not include project-generated traffic volumes. Volume data was collected July 8-10, Traffic Impact Study for the Grove Street Subdivision in the August 15, 2014 Page 8

13 Intersection Levels of Service Under existing conditions, all of the study intersections are operating acceptably overall. While the US 101 South off-ramp approach to Dry Creek Road is experiencing substantial delays during both the a.m. and p.m. peaks, this is not considered unacceptable because, overall the intersection is operating acceptably. The existing traffic volumes are shown in Figure 1. A summary of the intersection level of service calculations is contained in Table 3, and copies of the Level of Service calculations are provided in Appendix A. Study Intersection Approach Table 3 Existing Peak Hour Intersection Levels of Service AM Peak Existing Conditions PM Peak Delay LOS Delay LOS 1. US 101 South/Dry Creek Rd 10.5 B 18.9 C Southbound off-ramp 42.8 E ** F 2. US 101 North/Dry Creek Rd 5.9 A 5.1 A Northbound off-ramp 14.4 B 16.2 C 3. Grove St/Dry Creek Rd 23.3 C 24.5 C 4. Grove St/W Grant St 9.0 A 10.7 B Notes: Delay is measured in average seconds per vehicle; LOS = Level of Service; Results for minor approaches to two-way stop-controlled intersections are indicated in italics; ** = delay greater than 120 seconds Cumulative Conditions Future traffic volumes were obtained from the citywide build-out scenario presented in the Healdsburg 2030 General Plan Update Revised Draft Environmental Impact Report (DEIR), Christopher A. Joseph & Associates, January These volume projections were anticipated to reflect conditions upon full built-out of all vacant or underdeveloped parcels within the. Upon review it was determined that some of the existing volumes were slightly greater than the projected build-out volumes, so for the analysis the greater of existing or future volumes were used for all movements. Only the p.m. peak period was evaluated for the DEIR, so this analysis is limited to this same time period. Policy T-A-16 of the Healdsburg 2030 General Plan indicates that the City shall work with Caltrans, Sonoma County, and the Sonoma County Transportation Authority (SCTA) to plan and implement improvements to the US 101 Interchange at Dry Creek Road. As indicated in Table IV.O-6 of the DEIR, this would include signalization at both ramp intersections. This improvement was assumed to exist for purposes of the Cumulative Conditions analysis. Under the anticipated Future volumes, and with the signalization of the two ramp intersections, the study intersections are expected to operate acceptably. Cumulative volumes are shown in Figure 2 and operating conditions are summarized in Table 4. Traffic Impact Study for the Grove Street Subdivision in the August 15, 2014 Page 9

14 Grove Street 1 Cumulative 1 Project Dry Creek Road (25) (2) (168) (253) (174) (286) (795) 0(0) 0(0) 1(1) (2)1 (0)0 1(2) 3(4) 2 2 (305) (1044) 1(1) 4(6) (19) (393) (92) (581) (0)0 (3)1 (0)0 (4)2 Project Site (397) (186) (105) (61) (580) (127) 3 0(0) 2(4) 0(0) 0(0) 0(0) 2(5) (371) (572) (217) (247) (134) (153) (0)0 (0)0 (8)3 (7)5 (3)3 (4)3 4 (9) (230) (117) (82) (7) (133) 4 0(0) 8(11) 3(4) 2(4) 0(0) 0(0) 4 Grant Street (11) (8) (8) (10) (238) (139) (0)0 (0)0 (0)0 (0)0 (12)5 (0)0 North Not to Scale xx (xx) LEGEND Study Intersection A.M. Peak Hour Volume P.M. Peak Hour Volume Traffic Impact Study for the Grove Street Subdivision Figure 2 Cumulative and Project Traffic Volumes 060hea.ai 7/14

15 Table 4 Cumulative PM Peak Hour Levels of Service Study Intersection Delay LOS 1. US 101/Dry Creek Rd 28.4 C 2. US 101/Dry Creek Rd 40.9 D 3. Grove St/Dry Creek Rd 34.3 C 4. Grove St/W Grant St 11.7 B Notes: Delay is measured in average seconds per vehicle; LOS = Level of Service Project Description The proposed project consists of the subdivision that would create 30 separate parcels, 23 of which would be for single family homes. The remaining seven lots would be designated for mixed use with the Grove Street Mixed Use (GMU) designation. It was assumed that there would be single family dwellings on each of the 30 lots. The sizes of the commercial developments on the mixed use lots would likely vary from small office uses to larger retail spaces. A total of 12,000 square feet of commercial use was assumed for the entire subdivision. The proposed project site plan is shown in Figure 3. Trip Generation The anticipated trip generation for the proposed project was estimated using standard rates published by the Institute of Transportation Engineers (ITE) in Trip Generation Manual, 9 th Edition, 2012 for Single Family Detached Housing (ITE LU #210) along with Specialty Retail Center (ITE LU#826). Because there are no a.m. peak hour rates for the special retail land use, rates for a shopping center were used. Note that these general rates were applied as specific tenants were not identified at the time of the analysis, and also because tenants may change over time. Total Project Trip Generation The expected trip generation potential for the proposed project is indicated in Table 5. The proposed project is expected to generate an average of 818 new trips per day, including 35 trips during the a.m. peak hour and 63 during the p.m. peak hour. Because neither internal capture nor pass-by deductions were taken, the trip generation would be expected to be conservative. Table 5 Trip Generation Summary Land Use Units Daily AM Peak Hour PM Peak Hour Rate Trips Rate Trips In Out Rate Trips In Out Single Family Housing 30 du Specialty Retail* 12 ksf Total Notes: du = dwelling unit; ksf = 1,000 square feet * AM Rate from LU #820 (Shopping Center) Traffic Impact Study for the Grove Street Subdivision in the August 15, 2014 Page 11

16 Traffic Impact Study for the Grove Street Subdivision Figure 3 Site Plan 060hea.ai 8/14

17 Trip Distribution The pattern used to allocate new project trips to the street network was based on existing turning movements at the various study intersections. The applied distribution assumptions and resulting trips are shown in Table 6. Table 6 Trip Distribution Assumptions Route Percent Daily Trips AM Trips Traffic Impact Study for the Grove Street Subdivision in the August 15, 2014 Page 13 PM Trips South on Grove St 37% East on Dry Creek Rd 15% South on US % East on Grant St 13% North on Grove St 12% West on Dry Creek Rd 6% North on US 101 4% TOTAL 100% Intersection Operation Existing plus Project Conditions Upon the addition of project-related traffic to the Existing volumes, the study intersections are expected to continue operating acceptably under the standards applied. These results are summarized in Table 7. Project traffic volumes are shown in Figure 2. Table 7 Existing and Existing plus Project Peak Hour Intersection Levels of Service Study Intersection Existing Conditions Existing plus Project Approach AM Peak PM Peak AM Peak PM Peak Delay LOS Delay LOS Delay LOS Delay LOS 1. US 101S/Dry Creek Rd 10.5 B 18.9 C 11.7 B 21.3 C Southbound off-ramp 42.8 E ** F 50.4 F ** F 2. US 101N/Dry Creek Rd 5.9 A 5.1 A 5.9 A 5.2 A Northbound off-ramp 14.4 B 16.2 C 14.5 B 16.6 C 3. Grove St/Dry Creek Rd 23.3 C 24.5 C 23.5 C 25.0 C 4. Grove St/W Grant St 9.0 A 10.7 B 9.1 A 11.0 B Notes: Delay is measured in average seconds per vehicle; LOS = Level of Service; Results for minor approaches to two-way stop-controlled intersections are indicated in italics; ** = delay greater than 120 seconds Finding: The study intersections are expected to continue operating acceptably at the same levels of service overall upon the addition of project-generated traffic.

18 Cumulative plus Project Conditions Upon the addition of project-generated traffic to the anticipated Future volumes, and with the planned improvements, the study intersections are expected to operate acceptably. The Future plus Project operating conditions are summarized in Table 8. Table 8 Cumulative and Cumulative plus Project PM Peak Hour Levels of Service Study Intersection Cumulative Conditions Cumulative plus Project Delay LOS Delay LOS 1. US 101/Dry Creek Rd 28.4 C 28.7 C 2. US 101/Dry Creek Rd 40.9 D 42.1 D 3. Grove St/Dry Creek Rd 34.3 C 35.0 C 4. Grove St/W Grant St 11.7 B 12.0 B Notes: Delay is measured in average seconds per vehicle; LOS = Level of Service Finding: The study intersections would continue operating acceptably with project traffic added, at the same Levels of Service as under Cumulative No Project Conditions. Recommendation: The project applicant should contribute proportional share funding towards the planned improvements at the US 101/Dry Creek Road interchange. Application of the Caltrans proportional share calculation format indicates that the project should contribute 1.7 percent towards the US 101 South ramp intersection and 1.9 percent for the US 101 North ramp intersection. A copy of the calculation is provided in Appendix B. Traffic Impact Study for the Grove Street Subdivision in the August 15, 2014 Page 14

19 Alternative Modes Alternative Modes Pedestrian Facilities Given the proximity of schools, residential and retail uses surrounding the site, it is reasonable to assume that some project residents, patrons and employees would want to walk, bicycle, and/or utilize transit to reach the project site. Project Site A sidewalks does not exist along the project frontage, but is proposed as part of the project separated from the street by a 5-foot planter strip. The proposed roundabout will provide a connection between the sidewalk along the project site and the existing asphalt path on the east side of Grove Street. Finding: Pedestrian facilities serving the project site are currently inadequate. Recommendation: A crossing of Grove Street should be provided at the site s entrance to connect to existing pedestrian facilities on the easterly side of the street. Further, frontage improvements should include a sidewalk and planter strip. Bicycle Facilities Grove Street is planned as a Class III bike route per the Healdsburg Bicycle & Pedestrian Master Plan. The site s frontage improvements include an 8-foot parking lane adjacent to a 12-foot travel lane that will be shared by vehicles and bicyclists. Signing should be provided to indicate the roadway s Class III status. With this addition to existing bicycle facilities, together with shared use of minor streets, there would be adequate access for bicyclists. Recommendation: In order to achieve adequate bicycle facilities serving the project site, frontage improvements should include signage indicating that Grove Street is a Class III bike route. Additionally, commercial development should provide bicycle parking that meets the City s requirements. Traffic Impact Study for the Grove Street Subdivision in the August 15, 2014 Page 15

20 Access and Circulation Site Access Access to the project site is proposed via a new street connection to Grove Street. Through discussions with City staff it was determined that a mini-roundabout is desired to provide access to the site as well as to calm traffic and support the concepts of the Grove Street Neighborhood Plan. Mini-Roundabouts are small roundabouts with a fully traversable central island. They are most commonly used in low-speed urban environments with average operating speeds of 30 mph or less. In retrofit applications, mini-roundabouts are relatively inexpensive because they typically require minimal additional pavement at intersecting roads and minor widening at the corner curbs. (Roundabouts: An Informational Guide, NCHRP Report 672). The has endorsed the use of a mini-roundabout in order to provide a traffic calming element in the corridor. Consideration was also given to the use of all-way stop controls at the new intersection; however, due to the negative greenhouse gas impacts associated with the need for all vehicles to stop, the mini-roundabout is seen as a superior alternative. A preliminary layout has been prepared that provides adequate access for trucks while still regulating travel speeds for drivers traveling on Grove Street, and is provided in Figure 4. Analysis indicates that the mini-roundabout would operate at LOS A during the evening peak period under both short-term and cumulative volumes, with speeds regulated to an average of between 23 and 24 mph. A copy of the calculations is provided in Appendix C. Plate 1 Sample Layout Plate 2 Example Installation Traffic Impact Study for the Grove Street Subdivision in the August 15, 2014 Page 16

21 crosswalks set back 20' from yield line fully mountable center island 70' inscribed diameter non-mountable splitter islands deflection needed on northbound approach Grove St North Not to Scale Traffic Impact Study for the Grove Street Subdivision Figure 4 Farmstand Mini-Roundabout Concept 060hea.ai 7/14

22 Conclusions and Recommendations Conclusions The proposed subdivision would allow for the creation of 30 lots, to include 23 zoned for single family residential uses and seven zoned for mixed use. It was assumed that each of the 30 lots would be developed with a single family dwelling; an additional 12,000 square feet of commercial space were assumed for the seven mixed use lots. The project as envisioned would be expected to generate 818 trips on a daily basis, including 35 during the morning peak hour and 63 during the evening peak hour. While the commercial components would likely attract some trips from traffic passing the site on Grove Street, no deductions were taken to provide a more conservative analysis. The four study intersections currently operate acceptably under the standards applied, and are expected to continue doing so with project trips added. With the signalization of the Dry Creek Road interchange, as planned, the study intersections would all continue to operate acceptably under future volumes and with project-added trips. Existing facilities for pedestrians and bicyclists are discontinuous and inadequate. The proposed mini-roundabout would improve conditions as it would provide a crossing of Grove Street at the project access intersection. The sidewalk proposed along the project s frontage will also improve pedestrian access. A mini-roundabout is proposed at the new intersection created on Grove Street by the project. It is anticipated to operate acceptably and provide a traffic calming effect, which is desirable to address ongoing concerns relative to the speed of traffic along this roadway. Recommendations The project applicant should contribute a proportional share of 1.7 and 1.9 percent towards the costs of planned improvements at US 101 South/Dry Creek Road and US 101 North/Dry Creek Road, respectively. The sidewalk should be constructed on the west side of Grove Street along project site s frontage, as proposed. Bike parking facilities should be provided at all commercial sites to meet the City s requirements. The mini-roundabout should be designed to provide access, as proposed. Traffic Impact Study for the Grove Street Subdivision in the August 15, 2014 Page 18

23 Study Participants and References Study Participants Principal in Charge: Transportation Planner: Engineering Intern: Technician/Graphics: Technician/Design: Editing/Formatting: Review: Dalene J. Whitlock, PE, PTOE Zack Matley, AICP Allison Jaromin Deborah J. Mizell William Petker, EIT Angela McCoy Mark Spencer, TE References Grove Street Neighborhood Plan, Earthcraft Planning Services, 2000 Healdsburg 2030 General Plan Update Revised Draft Environmental Impact Report (DEIR), Christopher A. Joseph & Associates, 2009 Healdsburg 2030 General Plan,, 2011 Healdsburg Bicycle & Pedestrian Master Plan, Sonoma County Transportation Authority, 2008 Highway Capacity Manual, Transportation Research Board, 2000 Highway Design Manual, 6 th Edition, California Department of Transportation, 2012 Roundabouts: An Informational Guide, 2 nd Edition, National Cooperative Highway Research Program (NCHRP) Report No. 672, Transportation Research Board, 2010 Trip Generation Manual, 9 th Edition, Institute of Transportation Engineers, 2012 HEA060 Traffic Impact Study for the Grove Street Subdivision in the August 15, 2014 Page 19

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25 Appendix A Intersection Level of Service Calculations Traffic Impact Study for the Grove Street Subdivision in the August 2014

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27 AM Existing Mon Jul 14, :03:31 Page 2-1 AM Peak Hour - Existing Conditions Level Of Service Computation Report 2000 HCM Unsignalized Method (Base Volume Alternative) Intersection #1 US 101 SB Ramps/Dry Creek Rd Average Delay (sec/veh): 10.5 Worst Case Level Of Service: E[ 42.8] Street Name: US 101 SB Ramps Dry Creek Rd Approach: North Bound South Bound East Bound West Bound Movement: L - T - R L - T - R L - T - R L - T - R Control: Stop Sign Stop Sign Uncontrolled Uncontrolled Rights: Include Include Include Include Lanes: ! Volume Module: >> Count Date: 8 Jul 2014 << 8:00-9:00 am Base Vol: Growth Adj: Initial Bse: User Adj: PHF Adj: PHF Volume: Reduct Vol: FinalVolume: Critical Gap Module: Critical Gp:xxxxx xxxx xxxxx xxxxx xxxx xxxxx 4.1 xxxx xxxxx FollowUpTim:xxxxx xxxx xxxxx xxxxx xxxx xxxxx 2.2 xxxx xxxxx Capacity Module: Cnflict Vol: xxxx xxxx xxxxx xxxx xxxx xxxxx 189 xxxx xxxxx Potent Cap.: xxxx xxxx xxxxx xxxx xxxx xxxxx 1397 xxxx xxxxx Move Cap.: xxxx xxxx xxxxx xxxx xxxx xxxxx 1397 xxxx xxxxx Volume/Cap: xxxx xxxx xxxx xxxx xxxx xxxx 0.28 xxxx xxxx Level Of Service Module: 2Way95thQ: xxxx xxxx xxxxx xxxx xxxx xxxxx xxxx xxxx xxxxx 1.2 xxxx xxxxx Control Del:xxxxx xxxx xxxxx xxxxx xxxx xxxxx xxxxx xxxx xxxxx 8.6 xxxx xxxxx LOS by Move: * * * * * * * * * A * * Movement: LT - LTR - RT LT - LTR - RT LT - LTR - RT LT - LTR - RT Shared Cap.: xxxx xxxx xxxxx xxxx 242 xxxxx xxxx xxxx xxxxx xxxx xxxx xxxxx SharedQueue:xxxxx xxxx xxxxx xxxxx 3.9 xxxxx xxxxx xxxx xxxxx 1.2 xxxx xxxxx Shrd ConDel:xxxxx xxxx xxxxx xxxxx 42.8 xxxxx xxxxx xxxx xxxxx 8.6 xxxx xxxxx Shared LOS: * * * * E * * * * A * * ApproachDel: xxxxxx 42.8 xxxxxx xxxxxx ApproachLOS: * E * * Note: Queue reported is the number of cars per lane. PM Existing Mon Jul 14, :03:35 Page 2-1 PM Peak Hour - Existing Conditions Level Of Service Computation Report 2000 HCM Unsignalized Method (Base Volume Alternative) Intersection #1 US 101 SB Ramps/Dry Creek Rd Average Delay (sec/veh): 18.9 Worst Case Level Of Service: F[132.8] Street Name: US 101 SB Ramps Dry Creek Rd Approach: North Bound South Bound East Bound West Bound Movement: L - T - R L - T - R L - T - R L - T - R Control: Stop Sign Stop Sign Uncontrolled Uncontrolled Rights: Include Include Include Include Lanes: ! Volume Module: >> Count Date: 8 Jul 2014 << 4:00-5:00 pm Base Vol: Growth Adj: Initial Bse: User Adj: PHF Adj: PHF Volume: Reduct Vol: FinalVolume: Critical Gap Module: Critical Gp:xxxxx xxxx xxxxx xxxxx xxxx xxxxx 4.1 xxxx xxxxx FollowUpTim:xxxxx xxxx xxxxx xxxxx xxxx xxxxx 2.2 xxxx xxxxx Capacity Module: Cnflict Vol: xxxx xxxx xxxxx xxxx xxxx xxxxx 383 xxxx xxxxx Potent Cap.: xxxx xxxx xxxxx xxxx xxxx xxxxx 1187 xxxx xxxxx Move Cap.: xxxx xxxx xxxxx xxxx xxxx xxxxx 1187 xxxx xxxxx Volume/Cap: xxxx xxxx xxxx xxxx xxxx xxxx 0.38 xxxx xxxx Level Of Service Module: 2Way95thQ: xxxx xxxx xxxxx xxxx xxxx xxxxx xxxx xxxx xxxxx 1.8 xxxx xxxxx Control Del:xxxxx xxxx xxxxx xxxxx xxxx xxxxx xxxxx xxxx xxxxx 9.9 xxxx xxxxx LOS by Move: * * * * * * * * * A * * Movement: LT - LTR - RT LT - LTR - RT LT - LTR - RT LT - LTR - RT Shared Cap.: xxxx xxxx xxxxx xxxx 139 xxxxx xxxx xxxx xxxxx xxxx xxxx xxxxx SharedQueue:xxxxx xxxx xxxxx xxxxx 6.9 xxxxx xxxxx xxxx xxxxx 1.8 xxxx xxxxx Shrd ConDel:xxxxx xxxx xxxxx xxxxx 133 xxxxx xxxxx xxxx xxxxx 9.9 xxxx xxxxx Shared LOS: * * * * F * * * * A * * ApproachDel: xxxxxx xxxxxx xxxxxx ApproachLOS: * F * * Note: Queue reported is the number of cars per lane.

28 AM Existing Mon Jul 14, :03:31 Page 3-1 AM Peak Hour - Existing Conditions Level Of Service Computation Report 2000 HCM Unsignalized Method (Base Volume Alternative) Intersection #2 US 101 NB Ramps/Dry Creek Rd Average Delay (sec/veh): 5.9 Worst Case Level Of Service: B[ 14.4] Street Name: US 101 NB Ramps Dry Creek Rd Approach: North Bound South Bound East Bound West Bound Movement: L - T - R L - T - R L - T - R L - T - R Control: Stop Sign Stop Sign Uncontrolled Uncontrolled Rights: Include Include Include Include Lanes: 0 0 1! Volume Module: >> Count Date: 9 Jul 2014 << 7:45-8:45 am Base Vol: Growth Adj: Initial Bse: User Adj: PHF Adj: PHF Volume: Reduct Vol: FinalVolume: Critical Gap Module: Critical Gp: xxxxx xxxx xxxxx 4.1 xxxx xxxxx xxxxx xxxx xxxxx FollowUpTim: xxxxx xxxx xxxxx 2.2 xxxx xxxxx xxxxx xxxx xxxxx Capacity Module: Cnflict Vol: xxxx xxxx xxxxx 628 xxxx xxxxx xxxx xxxx xxxxx Potent Cap.: xxxx xxxx xxxxx 964 xxxx xxxxx xxxx xxxx xxxxx Move Cap.: xxxx xxxx xxxxx 964 xxxx xxxxx xxxx xxxx xxxxx Volume/Cap: xxxx xxxx xxxx 0.01 xxxx xxxx xxxx xxxx xxxx Level Of Service Module: 2Way95thQ: xxxx xxxx xxxxx xxxx xxxx xxxxx 0.0 xxxx xxxxx xxxx xxxx xxxxx Control Del:xxxxx xxxx xxxxx xxxxx xxxx xxxxx 8.8 xxxx xxxxx xxxxx xxxx xxxxx LOS by Move: * * * * * * A * * * * * Movement: LT - LTR - RT LT - LTR - RT LT - LTR - RT LT - LTR - RT Shared Cap.: xxxx 980 xxxxx xxxx xxxx xxxxx xxxx xxxx xxxxx xxxx xxxx xxxxx SharedQueue:xxxxx 4.4 xxxxx xxxxx xxxx xxxxx 0.0 xxxx xxxxx xxxxx xxxx xxxxx Shrd ConDel:xxxxx 14.4 xxxxx xxxxx xxxx xxxxx 8.8 xxxx xxxxx xxxxx xxxx xxxxx Shared LOS: * B * * * * A * * * * * ApproachDel: 14.4 xxxxxx xxxxxx xxxxxx ApproachLOS: B * * * Note: Queue reported is the number of cars per lane. PM Existing Mon Jul 14, :03:35 Page 3-1 PM Peak Hour - Existing Conditions Level Of Service Computation Report 2000 HCM Unsignalized Method (Base Volume Alternative) Intersection #2 US 101 NB Ramps/Dry Creek Rd Average Delay (sec/veh): 5.1 Worst Case Level Of Service: C[ 16.2] Street Name: US 101 NB Ramps Dry Creek Rd Approach: North Bound South Bound East Bound West Bound Movement: L - T - R L - T - R L - T - R L - T - R Control: Stop Sign Stop Sign Uncontrolled Uncontrolled Rights: Include Include Include Include Lanes: 0 0 1! Volume Module: >> Count Date: 10 Jul 2014 << 4:15-5:15 pm Base Vol: Growth Adj: Initial Bse: User Adj: PHF Adj: PHF Volume: Reduct Vol: FinalVolume: Critical Gap Module: Critical Gp: xxxxx xxxx xxxxx 4.1 xxxx xxxxx xxxxx xxxx xxxxx FollowUpTim: xxxxx xxxx xxxxx 2.2 xxxx xxxxx xxxxx xxxx xxxxx Capacity Module: Cnflict Vol: xxxx xxxx xxxxx 887 xxxx xxxxx xxxx xxxx xxxxx Potent Cap.: xxxx xxxx xxxxx 772 xxxx xxxxx xxxx xxxx xxxxx Move Cap.: xxxx xxxx xxxxx 772 xxxx xxxxx xxxx xxxx xxxxx Volume/Cap: xxxx xxxx xxxx 0.02 xxxx xxxx xxxx xxxx xxxx Level Of Service Module: 2Way95thQ: xxxx xxxx xxxxx xxxx xxxx xxxxx 0.1 xxxx xxxxx xxxx xxxx xxxxx Control Del:xxxxx xxxx xxxxx xxxxx xxxx xxxxx 9.7 xxxx xxxxx xxxxx xxxx xxxxx LOS by Move: * * * * * * A * * * * * Movement: LT - LTR - RT LT - LTR - RT LT - LTR - RT LT - LTR - RT Shared Cap.: xxxx 850 xxxxx xxxx xxxx xxxxx xxxx xxxx xxxxx xxxx xxxx xxxxx SharedQueue:xxxxx 4.6 xxxxx xxxxx xxxx xxxxx 0.1 xxxx xxxxx xxxxx xxxx xxxxx Shrd ConDel:xxxxx 16.2 xxxxx xxxxx xxxx xxxxx 9.7 xxxx xxxxx xxxxx xxxx xxxxx Shared LOS: * C * * * * A * * * * * ApproachDel: 16.2 xxxxxx xxxxxx xxxxxx ApproachLOS: C * * * Note: Queue reported is the number of cars per lane.

29 AM Existing Mon Jul 14, :03:31 Page 4-1 AM Peak Hour - Existing Conditions Level Of Service Computation Report 2000 HCM Operations Method (Base Volume Alternative) Intersection #3 Grove St/Dry Creek Rd Cycle (sec): 100 Critical Vol./Cap.(X): Loss Time (sec): 12 Average Delay (sec/veh): 23.3 Optimal Cycle: 44 Level Of Service: C Street Name: Grove St Dry Creek Rd Approach: North Bound South Bound East Bound West Bound Movement: L - T - R L - T - R L - T - R L - T - R Control: Permitted Permitted Protected Protected Rights: Include Include Include Include Min. Green: Y+R: Lanes: ! Volume Module: >> Count Date: 15 Apr 2014 << 7:45-8:45 am Base Vol: Growth Adj: Initial Bse: User Adj: PHF Adj: PHF Volume: Reduct Vol: Reduced Vol: PCE Adj: MLF Adj: FinalVolume: Saturation Flow Module: Sat/Lane: Adjustment: Lanes: Final Sat.: Capacity Analysis Module: Vol/Sat: Crit Moves: **** **** **** Green/Cycle: Volume/Cap: Delay/Veh: User DelAdj: AdjDel/Veh: LOS by Move: C C C C C C D B B D B B HCM2k95thQ: Note: Queue reported is the number of cars per lane. PM Existing Mon Jul 14, :03:35 Page 4-1 PM Peak Hour - Existing Conditions Level Of Service Computation Report 2000 HCM Operations Method (Base Volume Alternative) Intersection #3 Grove St/Dry Creek Rd Cycle (sec): 100 Critical Vol./Cap.(X): Loss Time (sec): 12 Average Delay (sec/veh): 24.5 Optimal Cycle: 51 Level Of Service: C Street Name: Grove St Dry Creek Rd Approach: North Bound South Bound East Bound West Bound Movement: L - T - R L - T - R L - T - R L - T - R Control: Permitted Permitted Protected Protected Rights: Include Include Include Include Min. Green: Y+R: Lanes: ! Volume Module: >> Count Date: 15 Apr 2014 << 4:30-5:30 pm Base Vol: Growth Adj: Initial Bse: User Adj: PHF Adj: PHF Volume: Reduct Vol: Reduced Vol: PCE Adj: MLF Adj: FinalVolume: Saturation Flow Module: Sat/Lane: Adjustment: Lanes: Final Sat.: Capacity Analysis Module: Vol/Sat: Crit Moves: **** **** **** Green/Cycle: Volume/Cap: Delay/Veh: User DelAdj: AdjDel/Veh: LOS by Move: C C C C C C D B B D B B HCM2k95thQ: Note: Queue reported is the number of cars per lane.

30 AM Existing Mon Jul 14, :03:31 Page 5-1 AM Peak Hour - Existing Conditions Level Of Service Computation Report 2000 HCM 4-Way Stop Method (Base Volume Alternative) Intersection #4 Grove St/Grant St Cycle (sec): 100 Critical Vol./Cap.(X): Loss Time (sec): 0 Average Delay (sec/veh): 9.0 Optimal Cycle: 0 Level Of Service: A Street Name: Grove St Grant St Approach: North Bound South Bound East Bound West Bound Movement: L - T - R L - T - R L - T - R L - T - R Control: Stop Sign Stop Sign Stop Sign Stop Sign Rights: Include Include Include Include Min. Green: Lanes: ! ! ! 0 0 Volume Module: >> Count Date: 15 Apr 2014 << 8:00-9:00 am Base Vol: Growth Adj: Initial Bse: User Adj: PHF Adj: PHF Volume: Reduct Vol: Reduced Vol: PCE Adj: MLF Adj: FinalVolume: Saturation Flow Module: Adjustment: Lanes: Final Sat.: Capacity Analysis Module: Vol/Sat: Crit Moves: **** **** **** **** Delay/Veh: Delay Adj: AdjDel/Veh: LOS by Move: A A A A A A A A A A A A ApproachDel: Delay Adj: ApprAdjDel: LOS by Appr: A A A A AllWayAvgQ: Note: Queue reported is the number of cars per lane. PM Existing Mon Jul 14, :03:35 Page 5-1 PM Peak Hour - Existing Conditions Level Of Service Computation Report 2000 HCM 4-Way Stop Method (Base Volume Alternative) Intersection #4 Grove St/Grant St Cycle (sec): 100 Critical Vol./Cap.(X): Loss Time (sec): 0 Average Delay (sec/veh): 10.7 Optimal Cycle: 0 Level Of Service: B Street Name: Grove St Grant St Approach: North Bound South Bound East Bound West Bound Movement: L - T - R L - T - R L - T - R L - T - R Control: Stop Sign Stop Sign Stop Sign Stop Sign Rights: Include Include Include Include Min. Green: Lanes: ! ! ! 0 0 Volume Module: >> Count Date: 15 Apr 2014 << 4:00-5:00 pm Base Vol: Growth Adj: Initial Bse: User Adj: PHF Adj: PHF Volume: Reduct Vol: Reduced Vol: PCE Adj: MLF Adj: FinalVolume: Saturation Flow Module: Adjustment: Lanes: Final Sat.: Capacity Analysis Module: Vol/Sat: Crit Moves: **** **** **** **** Delay/Veh: Delay Adj: AdjDel/Veh: LOS by Move: B B A B B B A A A B B B ApproachDel: Delay Adj: ApprAdjDel: LOS by Appr: A B A B AllWayAvgQ: Note: Queue reported is the number of cars per lane.