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HomeMy WebLinkAbout29A TheLakesatValleyWest_TIS_1-27-15 - Part 1 THE LAKES AT VALLEY WEST TRAFFIC IMPACT ANALYSIS SUBMITTED TO: CITY OF BOZEMAN JANUARY 2015 PREPARED BY: Bill White, Senior Transportation Planner 2880 Technology Blvd W PO Box 1113 Bozeman, MT 59771 406.587.0721 MMI PROJECT #: 5352.003 January 2015 Page i The Lakes at Valley West Traffic Impact Study TABLE OF CONTENTS 1 Introduction ................................................................................................................................ 1  1.1 Project Description .......................................................................................................... 1  1.2 Analysis Scope and Methodology ................................................................................. 4  2 Existing Conditions ................................................................................................................... 7  2.1 Roadway Network ........................................................................................................... 7  2.2 Traffic Counts ................................................................................................................... 8  2.3 Traffic Operations .......................................................................................................... 11  2.4 Collision Histories .......................................................................................................... 11  3 Year 2024 Growth Rate Forecasts ...................................................................................... 13 3.1 Roadway Network ......................................................................................................... 13 3.2 Traffic Forecasts ............................................................................................................ 13  3.3 Traffic Operations .......................................................................................................... 22  4 Year 2024 Pipeline Project Forecasts ........................................................................................ 23  4.1 Roadway Network ......................................................................................................... 23  4.2 Traffic Forecasts ............................................................................................................ 23  4.3 Traffic Operations .......................................................................................................... 31  5 Improvements and Project Mitigation .................................................................................. 33 5.1 Cottonwood Drive/Durston Road Intersection .......................................................... 33  5.2 Durston Road Three Lane ............................................................................................ 33  5.3 Developer Proposal ....................................................................................................... 35  6 Summary and Conclusions ................................................................................................... 37  6.1 Traffic Forecasts and Capacity .................................................................................... 37  6.2 Improvement Recommendations and Mitigation ...................................................... 37 6.3 Summary ......................................................................................................................... 38  January 2015 Page ii The Lakes at Valley West Traffic Impact Study TABLES AND FIGURES TABLES Table 1. Intersection Level of Service Criteria ......................................................................... 5 Table 2. Existing Intersection Geometrics and Traffic Controls ............................................... 8 Table 3 Existing LOS and Delay - AM and PM Peak Hours ................................................. 11 Table 4. Project Trip Generation Projections ......................................................................... 16 Table 5. Trip Distribution and Assignment Summaries .......................................................... 17 Table 6. Year 2024 LOS Summaries (Growth Rate) - AM and PM Peak Hours .................... 22 Table 7. Project Trip Generation Projections (Re-Summarized) ............................................ 24 Table 8. Total Entering Volume Comparisons ....................................................................... 31 Table 9. Year 2024 LOS Summaries (Pipeline) - AM and PM Peak Hours ........................... 31 FIGURES Figure 1. Site Location .................................................................................................................. 2 Figure 2. Site Plan ........................................................................................................................ 3 Figure 3. Existing Traffic Volumes – AM Peak Hour ..................................................................... 9 Figure 4. Existing Traffic Volumes – PM Peak Hour ................................................................... 10 Figure 5. Future Without Project Traffic Volumes (Growth Rate) - AM Peak Hour ..................... 14 Figure 6. Future Without Project Traffic Volumes (Growth Rate) - PM Peak Hour ..................... 15 Figure 7. Project Trip Assignments – AM Peak Hour ................................................................ 18 Figure 8. Project Trip Assignments – PM Peak Hour ................................................................ 19 Figure 9. Future With Project Traffic Volumes (Growth Rate) - AM Peak Hour .......................... 20 Figure 10. Future With Project Traffic Volumes (Growth Rate) - PM Peak Hour ........................ 21 Figure 11. Pipeline Project Trip Assignments – AM Peak Hour .................................................. 25 Figure 12. Pipeline Project Trip Assignments – PM Peak Hour .................................................. 26 Figure 13. Future Without Project Traffic Volumes (Pipeline Trips) - AM Peak Hour ................. 27 Figure 14. Future Without Project Traffic Volumes (Pipeline Trips) - PM Peak Hour ................. 28 Figure 15. Future With Project Traffic Volumes (Pipeline Trips) - AM Peak Hour ...................... 29 Figure 16. Future With Project Traffic Volumes (Pipeline Trips) - PM Peak Hour ...................... 30 Figure 17. Proposed Durston Road Cross Section ..................................................................... 35 Technical Appendix A: Glossary of Terms Technical Appendix B: Summary Traffic Counts Technical Appendix C: LOS Summary Worksheets Technical Appendix D: Pipeline Project Trip Assignments January 2015 Page 1 The Lakes at Valley West Traffic Impact Study 1 INTRODUCTION This report summarizes the Traffic Impact Study (TIS) performed for the Lakes at Valley West residential development proposed in Bozeman, Montana. The analysis identifies the transportation impacts of the proposed development on nearby City arterials and roadways; recommending improvements to address forecasted traffic growth and identifying project mitigations/participation towards these improvements. The scope and work program for this study was developed in coordination with engineering staff from the City of Bozeman, and was performed in accordance with the traffic impact study guidelines outlined in Article 41 – Submittal Materials and Requirements of Chapter 38 City of Bozeman Unified Development Code. The TIS was performed to support development and building permitting processes of the City. 1.1 PROJECT DESCRIPTION Valley West is a suburban community in northwest Bozeman generally bounded by Durston Road (north), Babcock Street (south), Ferguson Avenue (east), and the approximate Westgate Avenue alignment (west). The Lakes at Valley West is the proposed western piece of this community; occupying 65 acres with the potential for up to 300 single and multifamily homes to be developed within the timeframe of the next 5 to 10 years. The project is currently anticipated to include the development of 120 single family homes and 180 townhomes. Principal access to The Lakes at Valley West is proposed through new roadways extending into the site from Durston Avenue, proposed as Westgate Avenue, Laurel Parkway, and Westmorland Drive. All three connections are proposed as stop-controlled intersections, with stop signs located on northbound approaches to Durston Avenue. These are the more immediate project accesses developed in the next 10 years, with all being reviewed by this TIS. Secondary site access would eventually be provided through Westgate Avenue (local), Laurel Parkway (collector), and an additional unnamed local street connector, to the south boundary. Similarly, provision for connectivity to the adjacent westerly subdivision will also be provided via Westmorland Drive. The timing for the development of adjacent properties is unknown, though they are not likely to be developed for several years. As such, these secondary accesses were not reviewed by this study to assure a conservative analysis of the project impacts upon Durston Road. When these are developed, some congestion relief can be anticipated for site access and along Durston Road. The project is estimated to be developed in phases with approximately 30 homes constructed and occupied every two years. The project is located within an R-1 zone of Bozeman, is located within the Valley West Planned Unit Development, and has full completion and occupancy anticipated by year 2024. Figure 1 provides a vicinity map locating the project site. Figure 2 provides a site plan. January 2015 Page 4 The Lakes at Valley West Traffic Impact Study 1.2 ANALYSIS SCOPE AND METHODOLOGY The purpose of this TIS is to review the traffic and transportation impacts of the Lakes at Valley West development on arterials and recommend improvements and strategies, as needed, to mitigate these impacts in order to assure adequate transportation capacity. This section describes the primary scope and methods used to evaluate traffic conditions and determine potential improvements for the project study area. 1.2.1 Project Scope The scope for this study was established in coordination with City of Bozeman Engineering officials, and as per City Code. Per direction, this study quantifies traffic operations and capacity based on a review of intersection level-of-service (LOS). A TIS evaluates roadway capacity primarily through an examination of intersection operations/LOS as congestion and increased vehicle delays are experienced more rapidly at intersections versus road segments (between intersections). This is because the number and frequency of conflicts (i.e. turning vehicles and stopping or slowing movements) are higher and more complex at intersections versus roadway segments, and also because there are intentional stopped-delays that occur at intersections while travel is normally free-flowing between intersections on roadway segments. Per direction with staff, this study addresses LOS for the existing intersections of Westgate Avenue/Durston Road, Laurel Parkway/Durston Road, Cottonwood Road/Durston Road, and Cottonwood Road/W. Babcock Street and the future intersection of Westmorland Drive/Durston Road. The analysis was performed for the AM and PM peak/commute hours of the typical weekday, which are the highest hours of capacity demand within this region of Bozeman. As discussed later Section 2.2), typical count timeframes were extended to capture school activities; finding the traditional peak hours of the work commute experienced volumes that surpassed that of the peak generator hours of local schools. The project would be complete and occupied within 10 years. As such, a year 2024 analysis horizon (10 years from when traffic counts were collected) was reviewed for this study. Two forecast methodologies were used in this study to address a potential range of future traffic conditions within the City. These methodologies are summarized as follows: 1. Growth Rates. Traditionally TIS studies within Bozeman have been developed with background (non-project related) traffic growth forecasted with an annual growth rate applied to counts. Project trip assignments are then combined with baseline forecasts to generate future with project forecasts for the horizon/analysis year(s). Section 3 highlights traffic forecasts and operations/LOS results based on this traditional approach. 2. Pipeline Projects. Traffic forecasts developed using growth rates alone can sometimes miss the specific travel demands of new developments within a TIS study area. As such, it has become more common practice to build the assignments of these background developments, known as pipeline projects, into traffic forecasts. A more moderate baseline growth rate is applied to counts to reflect regional growth, and then project trip assignments are combined to generate future with project forecasts for the horizon year(s). Section 4 highlights traffic forecasts developed based upon pipeline project forecasting methodologies. As discussed later in this report, the different forecasting methodologies result in similar total entering volume (TEV) forecasts overall. The first method results in higher through forecasts January 2015 Page 5 The Lakes at Valley West Traffic Impact Study whereas the second method results in higher turning forecasts, resulting in conclusions and recommendations that are well vetted from varying forecasts perspectives. 1.2.2 Methodology - Intersection Operations Intersection capacity was evaluated using the level-of-service (LOS) methodologies of the Highway Capacity Manual (Transportation Research Board, 2010). The Highway Capacity Manual (HCM) is a nationally recognized and locally accepted method of measuring traffic flow and congestion for intersections. Criteria range from LOS A, indicating free-flow conditions with minimal vehicle delays, to LOS F, indicating congestion with significant vehicle delays (and operational failures). LOS for a signalized intersection is defined in terms of the average control delay experienced by all vehicles at the intersection, as measured over a specific time period, such as a peak hour. LOS for a one- or two-way stop controlled intersection or driveway is the function of average control delays experienced by vehicles in a particular approach or approach movement over a timeframe, such as a peak hour. Typically, the stopped approach or movement experiencing the worst LOS is reported. Finally, LOS at an all-way stop-controlled intersection is defined by the average control delays experienced by all vehicles at the intersection, as with signals, but the LOS thresholds are associated with delays for unsignalized versus signalized intersections. Table 1 outlines the LOS criteria for signalized and unsignalized intersections from the Highway Capacity Manual. As shown, LOS thresholds, as a function of delay, vary between signalized and unsignalized intersections. This is because driver tolerances for delay have been documented to be much higher at signalized versus unsignalized intersections. Table 1. Intersection Level of Service Criteria Level of Service Signalized: Control Delay (sec/veh) Unsignalized: Control Delay (sec/veh) A 10 10 B >10 – 20 10 - 15 C >20 – 35 15 - 25 D >35 – 55 25 - 35 E >55 – 80 35 - 50 F > 80 50 Source: Highway Capacity Manual (TRB, 2010) LOS was determined for this study using Synchro Version 8.0, (Trafficware, 2013). This software tool can apply the analysis methodologies of HCM 2010 and is a standard industry software application. LOS D is the typical threshold for signalized intersections. LOS E is allowed at unsignalized driveways and intersections (including all-way stops). 1.2.3 Methodology – Collision Histories Collision histories were reviewed for existing study intersections to determine whether safety issues occur as a result of operational or design issues, such as signal phase issues, sight January 2015 Page 6 The Lakes at Valley West Traffic Impact Study distance limitations, channelization alignment issues, etc. A location where numerous incidents are identified could indicate that a High Accident Location (HAL) may exist and would therefore require further safety analysis and ultimately improvement. An intersection may have a high number of accidents, but this is not as statistically relevant if the intersection also experiences high traffic volumes. Thus, an Intersection Collision Rate (ICR) quantifies severity based on the number of average accidents per year compared with average daily traffic (ADT), per the following equation: Intersection Collision Rate (ICR) = Average Accidents per Year * 1,000,000 (Collisions per million entering vehicles) 365 * Total Entering Intersection ADT The criteria for the evaluation of rates can vary between jurisdictions, but a typical guideline is that a corridor or intersection would require further evaluation/analysis if accident rates exceed 1.0 collisions per million entering vehicles. Typically, an HAL is not noted when rates are below this general guideline; or at the least it denotes where further review should be performed. January 2015 Page 7 The Lakes at Valley West Traffic Impact Study 2 EXISTING CONDITIONS This section describes existing traffic conditions within the project study area. Described are study roadways, current traffic volumes, existing operations and capacity conditions within the study area, and collision history analyses. 2.1 ROADWAY NETWORK As indicated, the study focuses on traffic operations for the existing intersections of Westgate Avenue/Durston Road, Laurel Parkway/Durston Road, Cottonwood Road/Durston Road, and Cottonwood Road/W. Babcock Street. Three of these roadways are City arterials/collectors, with a description of these roadways provided is as follows:  Cottonwood Road. This principal arterial has a two lane cross section north of and four separated lanes south of W. Babcock Street. Curb and gutter are located along the majority of both sides of the roadway between W. Babcock Street and Durston Road. There is little sidewalk along the east side of the roadway with approximately 1,500 feet along the west side between W. Babcock Street and Durston Road. The posted speed limit is 40 mph north of W. Babcock Street. The arterial supports 5,600 average daily traffic (ADT) south and 550 ADT north of Durston Road (count source: Traditions Subdivisions Phases 2 & 3 Residential Development TIS, Abelin Traffic Service 2014).  Durston Road. This is a two lane minor arterial within the study area (west of Cottonwood Road). Curb, gutter, and a bike lane have been constructed as development frontage improvements along the majority of the north side of this arterial (within the study area). However, only a one-foot paved shoulder is located along undeveloped section of the south side. Separated sidewalk has been constructed as frontage improvements for approximately 1,250 feet along the north side of the roadway, between Cottonwood Road and approximately Rosa Way, and for 1,150 feet along the north side, between Laurel Parkway and Westgate Avenue. There is no sidewalk along the south side. The speed limit is 35 mph and the roadway supports 8,600 ADT within the study area (count source: Traditions Subdivisions Phases 2 & 3 Residential Development TIS, Abelin Traffic Service 2014).  W. Babcock Street. This collector arterial has a two lane cross section with curb, gutter, and bike lanes from Cottonwood Road extending to a terminus approximately 1,500 feet to the west. There are no sidewalks along the roadway. The posted speed limit is 30 mph and the roadway supports 800 ADT within the study area (count source: Norton East Range Phase III Residential Development TIS, Abelin Traffic Service 2014).  Westgate Avenue and Laurel Parkway. These local streets specifically serve developments, although Laurel Parkway is being developed to the cross section of a collector arterial, The importance of this roadway will increase in the future. Both roadways were developed with curb, gutter, and separated sidewalk section, along developed property fronts. The speed limit is posted 25 mph for both roadways. There is an ADT count of 2,800 on Laurel Parkway and no available count for Westgate Avenue (count source: Boulder Creek/Westbrook TIS, Abelin Traffic Service 2014). A summary of existing intersection turn lane locations and traffic control conditions (signal, one-way, two way, or all way stops) is provided on Table 2. Shown are different traffic movements at intersections and the whether a turn lane is provided. If no specific lane is shown, then turns January 2015 Page 8 The Lakes at Valley West Traffic Impact Study are performed from an adjacent, shared through-lane. Also indicated are traffic control conditions for the intersection. Controls and lanes are denoted with an “X”. Table 2. Existing Intersection Geometrics and Traffic Controls Intersection Traffic Control Intersection Geometrics Traffic Signal One-Way Stop Two-Way Stop All-Way Stop NB Left Turn Lane NB Right Turn Lane SB Left Turn Lane SB Right Turn Lane WB Left Turn Lane WB Right Turn Lane EB Left Turn Lane EB Right Turn Lane Cottonwood Rd/Durston Rd - - X - - - - - - - - - Westgate Ave/Durston Rd - - X - - - - - - - - - Laurel Parkway/Durston Rd - - X - - - X - - - - - Cottonwood Rd/W. Babcock St - - X - X X X - X - X - 2.2 TRAFFIC COUNTS Intersection turn movement counts were collected specifically for this study on Thursday December 4, 2014 for the intersections of Laurel Parkway/Durston Road, Cottonwood Road/Durston Road, and Cottonwood Road/W. Babcock Street. There are only 25 homes accessing Westgate Avenue and, as such, through volumes were extrapolated from Laurel Parkway/Durston Road intersection and turning movements were estimated using trip generation information summarized by the Institute of Transportation Engineers (ITE) Trip Generation Manual (9th Edition, 2012) for residential housing for the Westgate Avenue/Durston Road intersection. This is an acceptable practice on low-volume roadways. Turing movement traffic counts were performed in the morning between 7:00 and 9:00 AM and in the afternoon/evening between 3:00 PM to 6:00 PM in order to identify the AM and PM peak hours of commute/work traffic activity for each intersection. The resulting AM peak hour was noted to occur at the majority of intersections between 7:30 to 8:30 AM, with a 7:45 to 8:45 AM peak hour noted for Cottonwood Road/W. Babcock Street. The PM peak hour was noted between 4:45 to 5:45 PM at the majority of intersections, with a 4:30 to 5:30 PM peak hour noted for Laurel Parkway/Durston Road. Meadowlark Elementary is located in the study area north of Durston Road 650 feet east of Cottonwood Road. Primary school hours are from 8:30 AM to 3:30 PM; having peak generator hours (highest hours of school traffic) occurring between 7:45 to 8:45 AM and 3:00 to 4:00 PM. Counts were performed while school was in session. The AM peak hour of the work commute traffic and AM peak generator of the school overlapped within the study area; and therefore analyses stated later in this report address this occurrence. However, the PM peak hour of commute activity was nearly 20 percent higher in volume following the PM peak generator hour of school activities for study intersections. As such, this TIS correctly addresses the PM peak hour of commute activity as volume demands are higher versus the afternoon hours of school. Figure 3 and Figure 4 provide a summary of existing traffic volumes for study intersections during the AM and PM peak hour. Count worksheets are provided in Technical Appendix B. January 2015 Page 11 The Lakes at Valley West Traffic Impact Study 2.3 TRAFFIC OPERATIONS The LOS and capacity analyses were performed based on a review of the traffic volumes summarized in Section 2.2 and the geometric conditions described in Section 2.1. Table 3 provides a summary of LOS for the AM and PM peak hours. Also shown are average control vehicle delays for each intersection. Note again, LOS and control delays for stop controlled intersections are the function of the worse approach or movement. Table 3. Existing LOS and Delay - AM and PM Peak Hours Signalized Intersections AM Peak Hour PM Peak Hour LOS1 Delay LOS1 Delay Cottonwood Rd/Durston Rd D 30.5 sec D 25.0 sec Westgate Ave/Durston Rd B 10.6 sec B 10.8 sec Laurel Parkway/Durston Rd C 17.3 sec B 13.9 sec Cottonwood Rd/W. Babcock St B 14.1 sec B 12.7 sec LOS = Levels-of-Service Again, LOS E is the standard industry threshold for the operation of stop-controlled/unsignalized intersections. Therefore, all study intersections currently function within acceptable LOS ranges. This indicates that no capacity improvements would be warranted on the basis of existing traffic operations, as there is sufficient roadway capacity. LOS summary worksheets are provided in Section C of the Technical Appendix. 2.4 COLLISION HISTORIES Collision histories were reviewed to determine whether any unusual safety issues were noted at study intersections. Per typical industry approach, collision data was collected from the City of Bozeman for the most current three-year period available, which extends from January 1, 2011 to December 31, 2013. Collision histories were available for the Cottonwood Road/Durston Road, Laurel Parkway/Durston Road, and Cottonwood Road/W. Babcock Street intersections. A summary of the collision history review and analyses is as follows:  Cottonwood Road/Durston Road. Two collisions were noted for the three-year study period, which represents an average 0.67 collisions per year. From counts, we can estimate a TEV of 11,675 ADT, which calculates to a collision rate of 0.16 collisions per million entering vehicles. There was one head-on collision and one collision between eastbound and westbound left-turning vehicles. Collisions involved property damage only with no injuries.  Laurel Parkway/Durston Road. A single collision was noted during the three-year study period, which represents an average of 0.34 collisions per year. From counts, we can estimate a TEV of 10,000 ADT, which calculates to a collision rate of 0.09 collisions per million entering vehicles. This vehicle was driven into the ditch at night, with no collision with another vehicle. The accident involved property damage only with no injuries. January 2015 Page 12 The Lakes at Valley West Traffic Impact Study  Cottonwood Road/W. Babcock Street. A single collision was noted during the three-year study period, which represents an average of 0.34 collisions per year. From counts, we can estimate a TEV of 6,400 ADT, which calculates to a collision rate of 0.15 collisions per million entering vehicles. This collision involved a westbound left-turning vehicle colliding with a southbound through movement. The accident involved property damage only with no injuries. The review of collision histories suggests there are no HAL at study intersections as the ICR’s are minimal with no injuries noted at any study intersection. January 2015 Page 13 The Lakes at Valley West Traffic Impact Study 3 YEAR 2024 GROWTH RATE FORECASTS This section summarizes year 2024 traffic forecasts, as developed using the baseline growth rate. Also described are planned future roadway improvements and forecast traffic operations and capacity conditions based on these forecasts. 3.1 ROADWAY NETWORK There are three improvement projects poised for development within the study area. All projects are currently unfunded and, as such, were not reflected in analyses for Section 3 (Year 2024 Growth Rate Forecasts) or Section 4 (Year 2024 Pipeline Forecasts) as they provide capacity that cannot be counted upon (within any predicted timeframe). However, some discussion as to the benefit of these improvements is provided in Section 5 (Improvements and Project Mitigation). It is anticipated these improvements would be developed through a combination of frontage improvements and financial support via traffic impact fees, the City of Bozeman street budget, and grants. A summary of planned improvement projects is as follows:  Durston Road. This includes the widening of Durston Road from a two-lane to a three- lane section west of Cottonwood Road to Westgate Avenue and adding a center turn lane with bike lane along the southern edge of the arterial.  Cottonwood Road/Durston Road. A traffic signal or roundabout is ultimately planned at the Cottonwood Road/Durston Road intersection. With the signal, turn lanes could be developed to better accommodate turn movements.  Cottonwood Road. A separated, four-lane section would be developed north from W. Babcock Street to Durston Road, adding two through lanes with bike lanes. 3.2 TRAFFIC FORECASTS Baseline traffic forecasts were developed for this Section using a 3% annual growth rate provided by City of Bozeman Engineers. This growth rate was applied to year 2014 traffic volumes to generate year 2024 future without project traffic volumes for the AM and PM peak hours. A summary of baseline growth, year 2024 future without-project traffic forecasts is shown on Figure 5 for the AM peak hour and Figure 6 for the PM peak hour. January 2015 Page 16 The Lakes at Valley West Traffic Impact Study 3.2.1 Trip Generation Trip generation was predicted using the methods outlined in the Institute of Transportation Engineers (ITE) Trip Generation Manual (9th Edition, 2012). The Trip Generation Manual is a nationally recognized and locally accepted method for forecasting trip generation for a range of commercial, retail, and residential land uses. The forecasting methods were developed based on the survey of other existing land use developments located throughout the United States. Trip generation was determined using ITE Code 210 for single family homes and ITE Code 230 for Townhomes. The ITE describes these land uses as follows:  ITE Code 210 Single-Family Detached Housing - “includes all single-family detached homes on individual lots.”  ITE Code 230 Residential Condominium/Townhouse - “ownership units that have at least one other owned unit within the same building structure.” Trip generation was determined based on equations that estimate trips according to the number of dwelling units. Equations were used for this study for the following reasons: more than ten surveys/studies were used to develop ITE equations for these land uses; a resulting data regression analysis results in a fit in excess of 0.80 for both uses; and more conservative (higher) trip generation totals are provided. The Trip Generation Manual indicates equations should be met over rates when these criteria are met. Trips were for the weekday and AM and PM peak hours of the weekday, assuming the development and occupancy of 120 single family homes and 180 townhomes. A summary of resulting trip generation is provided on Table 4. Table 4. Project Trip Generation Projections Land Use (Units) Weekday AM Peak Hour PM Peak Hour In Out Total In Out Total Single Family Homes (120 units) 1,240 23 71 94 78 46 124 Townhomes (180 units) 1,070 14 69 83 65 32 97 Trip Totals 2,310 37 140 177 143 78 221 Source: Derived from equations provided in Trip Generation Manual (ITE, 2012) As shown, 2,310 trips would be generated during the typical weekday, with 177 trips generated during the AM peak hour and 221 trips generated during the PM peak hour. Peak hourly trips would comprise 17.2 percent of total daily trips. 3.2.2 Trip Distribution The distribution of trips was estimated to establish traffic forecasts for future LOS analyses. An imaginary cordon or screen line was assumed around the project vicinity encompassing the principal approach routes of Durston Road, Cottonwood Road, and W. Babcock Street. Individual average daily traffic (ADT) counts were compared with total ADT volumes on this cordon line (a total of 18,000 ADT was noted) to gain a sense of distribution patterns. Trip January 2015 Page 17 The Lakes at Valley West Traffic Impact Study distributions were proportioned to these primary approach routes in order to determine project trip assignments. A summary of this comparison is as follows:  Durston Road East. There is an ADT count of 8,600 ADT on Durston Road east of Cottonwood Road. This results in a distribution of approximately 50 percent when compared with total ADT along the cordon line.  Cottonwood Road South. There is an ADT count of 5,600 ADT on Cottonwood Road south of W. Babcock Street. This results in an approximate 30 percent distribution when compared with total ADT along the cordon line.  Durston Road West. Peak hourly to ADT ratios were developed for Durston Road East, and then used to estimate an ADT count of 3,000 ADT west of Westgate Avenue. This results in an approximate 15 percent distribution when compared with total ADT along the cordon line.  W. Babcock Street East. An approximate 800 ADT was noted for W. Babcock Street, with this road providing a viable albeit less direct route into Bozeman. A comparison results in an approximate 5 percent distribution when compared with total ADT along the cordon line. The remaining study road segments did not provide a typical approach to/from the study area and were therefore neglected in the distribution and assignment of trips. Project trips were then assigned to the study area based upon these distribution patterns. A summary of trip assignments is provided on Table 5 for the weekday, AM peak hour, and PM peak hour. Table 5. Trip Distribution and Assignment Summaries Location Distribution (Rounded) Assignments Daily Assignments AM Peak Assignments PM Peak Durston Rd W/of Westgate Ave 15.0% 345 27 33 Durston Rd E/of Cottonwood Drive 50.0% 1,155 88 111 Cottonwood Rd S/of W. Babcock St 30.0% 695 53 66 W. Babcock St E/of Cottonwood Rd 5.0% 115 9 11 Total Trip Assignments 100% 2,310 177 221 1. Distributions to/from west split between Elton Road, Upriver Drive, and Wellesley Avenue. Figure 7 provides a summary of intersection trip assignments for the AM peak hour and Figure 8 for the PM peak hour. Future without project traffic volumes and project trip assignments were combined to generate the future year 2024 traffic forecasts shown on Figure 9 and Figure 10 for the AM and PM peak hours. Again these forecasts were developed with the application of annual growth rates. January 2015 Page 22 The Lakes at Valley West Traffic Impact Study 3.3 TRAFFIC OPERATIONS The LOS and capacity analyses were performed based on a review of the traffic forecasts summarized in Section 3.2. As indicated, this analysis was performed based on current geometric conditions. Table 6 provides a summary of future without and with project LOS and control delays for the AM and PM peak hours. Table 6. Year 2024 LOS Summaries (Growth Rate) - AM and PM Peak Hours Future Without Project Future With-Project Signalized Intersections AM Peak Hour PM Peak Hour AM Peak Hour PM Peak Hour LOS1 Delay LOS1 Delay LOS1 Delay LOS1 Delay Cottonwood Rd/Durston Rd F 102.8 F 177.2 F 207.8 F >250.0 Westgate Ave/Durston Rd B 11.6 B 12.0 C 15.9 C 15.4 Laurel Parkway/Durston Rd D 30.4 C 19.3 F 164.1 F 61.4 Cottonwood Rd/W. Babcock St C 18.2 C 15.5 C 20.2 C 17.5 Westmorland Dr/Durston Rd -- -- -- -- C 15.3 C 16.9 LOS = Levels-of-Service As shown, the Cottonwood Road/Durston Road intersection is projected to function at LOS F by year 2024 during the AM and PM peak hours, as reviewed based on forecasts developed with growth rates. Similarly, the Laurel Parkway/Durston Road intersection is projected to operate at LOS F with the introduction of the fourth intersection approach during both peak hours. Note this LOS result is the function of delay experienced within the southbound approach, specifically the left-turn movement, at the intersection. All other intersections are projected to function with acceptable LOS during the AM and PM peak hours. January 2015 Page 23 The Lakes at Valley West Traffic Impact Study 4 YEAR 2024 PIPELINE PROJECT FORECASTS This section summarizes year 2024 traffic forecasts, as developed using pipeline project trip assignments. Reiterated are future roadway network changes and provided are forecast traffic operations and capacity conditions based on these forecasts. 4.1 ROADWAY NETWORK As indicated, the three-lane Durston Road project; the Cottonwood Road/Durston Road signal or roundabout project; and the Cottonwood Road four lane extension are improvements planned within the study area. However, as all projects are currently unfunded, they are not addressed with the analyses in this Section. Some discussion as to the benefit of these improvements is provided in Section 5 (Improvements and Project Mitigation). 4.2 TRAFFIC FORECASTS Future without project traffic forecasts were developed for this Section using a 1 percent annual growth rate combined with pipeline project trip assignments. The 1 percent growth rate addresses baseline traffic growth, meaning traffic growth not associated with specific developments within the study area. Pipeline projects again refer to vested land use projects that have been approved by local agencies, but are in the process of being developed. As such, the trips generated by these projects are not yet recorded in counts and need to be addressed in forecasts as they have rights to future capacity. A summary of pipeline projects are as follows:  Boulder Creek/Westbrook. This project includes the development of 233 single family residential units located north of Durston Road, ¼ mile west of Cottonwood Road. The traffic impact study for this development (Abelin Traffic Services, November 2013) indicates the project would generate 2,230 weekday trips with 175 trips generated during the AM peak hour and 235 trips during the PM peak hour. Of these trips, approximately 33 percent are expected off Cottonwood Road to/from the north of Durston Road, 11 percent off Cottonwood Road to/from the south of Babcock Street, 3 percent off Durston Road to/from the west of Westgate Avenue, 31 percent off Durston Road to/from the east of Cottonwood Drive, 11 percent off Laurel Parkway to/from the north of Durston Road, and 11 percent off W. Babcock Street to/from the east of Cottonwood Road.  Norton East Ranch Phase III. This project includes the development of 106 single family residential units located west of Laurel Parkway between Babcock Street and Fallon Street. The traffic impact study for this development (Abelin Traffic Services, June 2014) indicates the project would generate 1,014 weekday trips with 80 trips generated during the AM peak hour and 107 trips during the PM peak hour. Of these trips, approximately 4 percent are expected off Cottonwood Road to/from the north of Durston Road, 50 percent off Cottonwood Road to/from the south of Babcock Street, 10 percent off Durston Road to/from the west of Westgate Avenue, 24 percent off Durston Road to/from the east of Cottonwood Drive, and 13 percent off W. Babcock Street to/from the east of Cottonwood Road.  Traditions Subdivision Phases 2 & 3. This project includes the development of 98 single family residential units located north of Annie Street and west of Cottonwood January 2015 Page 24 The Lakes at Valley West Traffic Impact Study Road. The traffic impact study for this development (Abelin Traffic Services, September 2014) indicates the project would generate 938 weekday trips with 74 trips generated during the AM peak hour and 99 trips during the PM peak hour. Of these trips, approximately 47 percent are expected off Cottonwood Road to/from the north of Durston Road, 2 percent off Cottonwood Road to/from the south of Babcock Street, 1 percent off Durston Road to/from the west of Westgate Avenue, 26 percent off Durston Road to/from the east of Cottonwood Drive, 2 percent off Laurel Parkway to/from the north of Durston Road, and 12 percent off W. Babcock Street to/from the east of Cottonwood Road. Attached Figure 11 and Figure 12 provide a summary of pipeline project trip assignments for the AM and PM peak hours at study intersections. Pipeline trips were combined with baseline forecasts to develop the future without project traffic volumes, as shown on Figure 13 and Figure 14 for the peak hours. Specific pipeline project trip assignments are provided in Section D of the Technical Appendices. 4.2.1 Trip Generation & Distribution Again, trip generation was based on the methods of the (ITE) Trip Generation Manual (9th Edition, 2012). Trip generation was determined for 120 for single family homes 180 townhomes. Total project trip generation is again summarized on Table 7. Table 7. Project Trip Generation Projections (Re-summarized) Land Use (Units) Weekday AM Peak Hour PM Peak Hour In Out Total In Out Total Trip Totals 2,310 37 140 177 143 78 221 Source: Derived from equations provided in Trip Generation Manual (ITE, 2012) As indicated, the distribution of these project trips was based on a review of study area ADT trips. A summary of these distributions are again as follows:  Durston Road East. 50 percent to/from the east of Cottonwood Road.  Cottonwood Road South. 30 percent to/from the south of W. Babcock Street.  Durston Road West. 15 percent to/from the west of Westgate Avenue.  W. Babcock Street East. 5 percent to/from the east of Cottonwood Road. Project trip assignments are again summarized on figure 7 and figure 8 for the AM and PM peak hours of the typical weekday. 4.2.2 Forecasts and Volume Comparisons Trip assignments were combined with the future without project forecasts, as developed with pipeline project trips, to generate future with project traffic forecasts. A summary of the resulting future year 2024 future with project traffic forecasts shown on Figure 15 and Figure 16 for the AM and PM peak hours. January 2015 Page 31 The Lakes at Valley West Traffic Impact Study A comparison of traffic forecasts was performed between the two forecast methodologies summarized in Section 3 (Year 2024 Growth Rate Forecasts) or Section 4 (Year 2024 Pipeline Forecasts). Table 8 provides a summary of total entering volume forecasts, represented as percent annual growth rates calculated between existing and future Year 2024 volumes for existing study intersections. Table 8. Total Entering Volume Annual Growth Comparisons Signalized Intersections Growth Rates Pipeline Trips AM Peak PM Peak AM Peak PM Peak Cottonwood Rd/Durston Rd 4.2% 4.4% 4.6% 5.3% Westgate Ave/Durston Rd 4.6% 4.9% 3.2% 3.7% Laurel Parkway/Durston Rd 4.2% 5.1% 3.7% 4.1% Cottonwood Rd/W. Babcock St 3.8% 4.1% 3.7% 4.8% Weighted Average Annual Growth Rates 4.3% 4.7% 4.0% 4.8% As shown, average annual growth rates are similar between the forecast methodologies for study intersections. Thus, although there is some difference between through and turning movement forecasts, they result in similar growth projections. 4.3 TRAFFIC OPERATIONS The LOS and capacity analyses were performed based on a review of the traffic forecasts summarized in Section 4.2. Again, this analysis was performed based on the current geometric conditions as planned improvements are currently unfunded. Table 9 provides a summary of future without project LOS and control delays for the AM and PM peak hour, as based on pipeline project traffic forecasts. Table 9. Year 2024 Traffic Forecasts (Pipeline) - AM and PM Peak Hours Future Without Project Future With-Project Signalized Intersections AM Peak Hour PM Peak Hour AM Peak Hour PM Peak Hour LOS1 Delay LOS1 Delay LOS1 Delay LOS1 Delay Cottonwood Rd/Durston Rd F >250.0 F >250.0 F >250.0 F >250.0 Westgate Ave/Durston Rd B 11.7 B 11.4 C 14.5 B 14.4 Laurel Parkway/Durston Rd C 23.8 C 16.6 F 75.6 E 40.5 Cottonwood Rd/W. Babcock St C 19.6 C 18.1 C 21.8 C 20.8 Westmorland Dr/Durston Rd -- -- -- -- B 14.9 C 15.2 LOS = Levels-of-Service As before, the Cottonwood Road/Durston Road intersection is projected to function at LOS F by year 2024 during the AM and PM peak hours, as reviewed based on forecasts developed with January 2015 Page 32 The Lakes at Valley West Traffic Impact Study pipeline project assignments. As before, the Laurel Parkway/Durston Road intersection is projected to operate at LOS F with the introduction of the fourth intersection approach, except only during the AM peak hour. Again this LOS result is the function of delay experienced within the southbound approach, specifically the left-turn movement, at the intersection. All other intersections are projected to function with acceptable LOS during the AM and PM peak hours. Note the results of the LOS analysis yield similar operations/capacity results, despite the difference in forecasting methodologies. January 2015 Page 33 The Lakes at Valley West Traffic Impact Study 5 IMPROVEMENTS AND PROJECT MITIGATION Operational deficiencies (LOS exceptions) were noted for the Cottonwood Road/Durston Road and Laurel Parkway/Durston Road intersections. This section reviews and validates two improvements planned for the study area. 5.1 COTTONWOOD DRIVE/DURSTON ROAD INTERSECTION As indicated, a LOS deficiency has been noted for the Cottonwood Drive/Durston Road intersection. Traffic forecasts were reviewed incrementally between year 2014 and year 2024 during the more critical of the peak hour conditions/scenarios reviewed for this intersection, which was the AM peak hour of the pipeline forecast scenario. Thus, to accomplish the incremental analysis for this intersection:  60 units of The Lakes of Valley West development was reviewed incrementally (every two years) to an intermediate horizon year  The 1 percent annual growth rate compounded annually to this horizon year (every two years)  Plus, a 20 percent increment assignment of pipeline project trips to this incremental horizon year (every two years) Based on this incremental analysis, it was determined the intersection would function at LOS F by year 2016, indicating the need for some improvement within a two year timeframe. The installation of an all-way stop would mitigate this deficiency temporarily, delaying this deficiency approximately two years. Thus, the need for more rigorous signal or roundabout improvement would be needed by year 2018. As indicated previously, the City of Bozeman is planning to construct a traffic signal or roundabout at this intersection as funding permits in the future. Either improvement will fully address & correct LOS for this intersection; resulting in a LOS B/C operations under either forecast scenario for the AM and PM peak hours. An analysis was then performed to determine the proposed projects responsibility towards Cottonwood Drive/Durston Road intersection improvements. Per standard industry practices, a developments responsibility towards improvements is calculated on the bases of total entering volumes. Thus, the weighted average impact of project trip assignments versus forecast TEV is shown below:  (150+150+188+188) / (1,369+1,419+1,448+1,574) = 11.6% Given this calculation, the project comprises an average 11.6 percent of TEV at the intersection. As such, it is recommended the project participate in providing 32.0 percent of construction costs associated with improvement development. 5.2 DURSTON ROAD THREE LANE As indicated, the Laurel Parkway/Durston Road intersection is projected to function within the LOS F range during the peak hours according to both forecast scenarios. Although this conflict January 2015 Page 34 The Lakes at Valley West Traffic Impact Study does occur as the result of project construction, with the addition of the fourth/south leg, the LOS issue is actually due to the stopped delay associated with the southbound left-turn movement at the intersection. Between 226 and 247 southbound left-turns were noted between forecast scenarios during the AM peak hour with between 142 and 155 noted between forecasts during the PM peak hour; causing significant stopped delays. Traffic forecasts were reviewed incrementally between year 2014 and year 2024 during the more critical of the peak hour conditions/scenarios reviewed for this intersection, which was the AM peak hour of the growth rate forecast scenario. Thus, to accomplish the incremental analysis for this intersection:  60 units of The Lakes of Valley West development was reviewed incrementally (every two years) to an intermediate horizon year,  The 3 percent annual growth rate compounded annually to this horizon year (every two years), Based on this incremental analysis, it was determined the intersection would function at LOS F by year 2020, indicating the need for some improvement within a six-year timeframe. Typical improvements for LOS such as this include turning restrictions, the construction of a roundabout/signal, an alternative route, and/or the construction of a two-way left-turn lane (TWLTL) or center turn lane; of which the TWLTL and the signal/roundabout options seem the most appropriate given the situation. TWLTL. As indicated, City Engineers have planned to construct a TWLTL along Durston Road from Cottonwood to Westgate Avenue. With the appropriate channelization, this lane can offer turning capacity for intersections and driveways along the length of Durston Road, providing for the staged movements of left-turns from intersecting streets onto the arterial. The staging of left-turns promotes a concept known as two-stage gap acceptance. This improves LOS and reduces vehicle delay, as drivers deal with traffic conflicts from only one direction of travel at a time versus two. If channelized appropriately, this improvement would mitigate traffic operations back into the LOS D/E range during the year 2024 AM and PM peak hours. However, for this to serve as a TWLTL, no eastbound or westbound left-turn lanes can be striped at the intersection; rather only the TWLTL striping can be used. This is because southbound and northbound left turning vehicles would turn into a designated turn lane, which is prohibited. Even to this end, there may be a potential for traffic conflicts between especially westbound left and southbound left-turning movements. Therefore, City Engineers may not find this a desirable mitigation for LOS issues at the intersection. Per standard industry practices, a proportionate impact of roadway improvements, in this case TWLTL widening, is determined by comparing trip assignments versus forecast traffic volumes on the roadway in question. In this case, the weighted average impact of project trip assignments versus forecast assignments on Durston Road is shown below:  (140+140+175+175) / (933+834+1,006+912) = 17.1% Given this calculation, the project comprises an average 17.1 percent of total growth projected along Durston Road between Cottonwood Road and Laurel Parkway. As such, it is January 2015 Page 35 The Lakes at Valley West Traffic Impact Study recommended the project participate in providing 17.1 percent of construction costs associated with improvement development. Traffic Signal. A roundabout or traffic signal would be the more ideal mitigation for the intersection, if a TWLTL is deemed by City Engineers to be the wrong improvement. A signal or roundabout would elevate operations back into the LOS B range, which is a better result; although this project would not offer capacity benefits to other intersections or driveways along Durston Road as with the TWLTL. So there is a trade-off with this improvement. As indicated previously, a comparison of TEV trip assignments versus total forecasts is the measure for impacts for intersections with the comparison summarized as follows:  (152+152+190+190) / (973+877+1,050+961) = 17.7% Given this calculation, the project comprises an average 17.7 percent of total growth projected at the intersection. As such, it is recommended the project participate in providing 17.7 percent of construction costs associated with the development of a signal or roundabout, if required over a TWLTL. 5.3 DEVELOPER PROPOSAL The project proponent and developer for the Lakes at Valley West has offered to construct the third lane and bike lane for Durston Road extending nearly one mile between Cottonwood Road and Westgate Drive for the City of Bozeman. This would include the addition of 15 feet of pavement along the southern frontage of the current arterial with an 18-foot landscape area and 6-foot sidewalks, per the cross section shown below. Figure 17. Proposed Durston Road Cross-Section The expense with developing this paved section is much more considerable than 11.6 percent proportion of the Cottonwood Road/Durston Road intersection improvement and the 17.1 percent or 17.7 percent proportion of either Durston Road widening or Laurel Parkway/Durston Road improvements discussed above, respectively. Understanding this, City Engineers have indicated a willingness to enter into a “City of Bozeman Impact Fee Credit Agreement” with the project proponent to provide reimbursement for construction costs through traffic impact fees, the street budget, and/or through reimbursement of possible grants. January 2015 Page 36 The Lakes at Valley West Traffic Impact Study As such, the next step in the process (following the development of this TIS) is for a civil engineer to develop engineering and construction cost estimates for the improvements outlined in 5.1 and 5.2; the Cottonwood Road/Durston Road intersection and for Durston Road improvements and/or for the Laurel Parkway/Durston Road intersection. The proportionate allocations discussed in these chapters should then be compared against these costs to determine a project mitigation fee. The developer reimbursement would then be construction costs less the project mitigation fee. By way of a planning example (and by round numbers), let’s assume improvements to the Durston Road/Cottonwood Road intersection total $300,000. Let’s assume improvements to Durston Road have a construction cost of approximately $1,000,000. Thus, the proportionate mitigation fees for these projects would be ($300,000 * 11.6%) + ($1,000,000 * 17.1%) = $205,800 owed towards improvements. This would result in reimbursement of $1,000,000 - $205,800 = $794,200 back towards the developer. Again, this is an example and all construction costs should be reviewed by a civil engineer to document agreement details. January 2015 Page 37 The Lakes at Valley West Traffic Impact Study 6 SUMMARY AND CONCLUSIONS A 300-unit residential development is proposed south of Durston Road approximately ½ mile west of Cottonwood Road. Principal access to the development is proposed through Westgate Avenue, Laurel Parkway, and Westmorland Drive; all of which will extend south into The Lakes at Valley West. The development is located within an R-1 zone of Bozeman and also within the Valley West Planned Unit development. Project completion and occupancy is anticipated by year 2024. The project is anticipated to have a mix of 120 single family homes and 180 townhomes. The project is anticipated to generate 2,310 weekday trips with 177 trips generated during the AM peak hour and 221 trips generated during the PM peak hour. Approximately 50 percent of project trips are expected to/from the east of Cottonwood Road on Durston Road; 30 percent are expected on Cottonwood Road to/from the south of W. Babcock Street; 15 percent on Durston Road to/from the west of Westgate Avenue; and 5 percent on W. Babcock Street to/from the east of Cottonwood Road. 6.1 TRAFFIC FORECASTS AND CAPACITY The project is estimated to be complete and occupied within ten years, and as such, traffic forecasts were developed for year 2024 for the AM and PM peak hours of the typical weekday. Two forecast methodologies were used in this study, to address a potential range of future traffic conditions within the City. These methodologies are summarized as follows:  Growth Rates. Project trip assignments were developed with baseline forecasts, with baseline forecasts developed using a 3 percent growth rate.  Pipeline Projects. Project trip assignments were developed with baseline forecasts developed using a 1 percent growth rate plus the trip assignments generated by approved, but yet to be developed, “pipeline” development projects. Four existing and one new intersection was reviewed with this study; including the intersections of Westgate Avenue/Durston Road, Laurel Parkway/Durston Road, Cottonwood Road/Durston Road, and Cottonwood Road/W. Babcock Street and the future intersection of Westmorland Drive/Durston Road. Of these intersections, operational deficiencies (LOS exceptions) were noted for the Cottonwood Road/Durston Road and Laurel Parkway/Durston Road intersections. 6.2 IMPROVEMENT RECOMMENDATIONS AND MITIGATION A number of improvements are planned by City of Bozeman Engineers. These improvements were vetted by this study, and confirmed for both study intersections. The following measures were proposed to address capacity/operational issues, with project participation to include:  A traffic signal or roundabout is confirmed and recommended for the Durston Road/Cottonwood Road intersection, which is projected to experience unacceptable LOS by year 2016. An interim, all/four way stop can be developed to promote LOS for two additional years. However, the signal improvement would ultimately be required by year 2018, and would fully address operational issues at the intersection (promoting LOS B/C traffic operations). The project would have an 11.6% growth impact and recommended proportionate responsibility towards intersection improvements. January 2015 Page 38 The Lakes at Valley West Traffic Impact Study  A two-way left-turn lane (center turn lane) is confirmed along Durston Road between Cottonwood Road and Westgate Avenue. The analysis of the Laurel Parkway/Durston Road intersection indicates this improvement would be needed by year 2020. The TWLTL would promote a LOS D/F function for this intersection, as well as improve traffic operations for other intersections and driveways along Durston Road. The project would have an 17.1% growth impact and recommended proportionate responsibility towards Durston Road widening improvements.  Alternatively, a roundabout or signal could be constructed for Laurel Parkway/Durston Road if City Engineers determine the TWLTL is not the appropriate solution for the intersection. This focused improvement would elevate operations back into the LOS B range; however, this would not offer the benefit of the TWLTL for the remainder for Durston Road. The project would have an 17.7% growth impact and recommended proportionate responsibility towards intersection improvements, if a signal were selected over the TWLTL. As indicated in Section 5.3, the developer for The Lakes at Valley West has offered to construct the three lane section for Durston Road between Cottonwood Drive and Westgate Drive for the City of Bozeman, including a 15 foot paved section, an 18 foot landscape buffer, and a 6 foot sidewalk. The City of Bozeman indicated the willingness to enter into an agreement with the developer. The expense of this improvement will be considerably more than the proportionate impact/contribution of the improvements identified above. Thus, the developer will enter into a “City of Bozeman Impact Fee Credit Agreement” with the City to be reimbursed for construction costs, less the proportionate impacts/fees determined via the responsibilities identified above. A civil engineer should be used to finalize mitigation fees for this development, via construction cost estimates compared with the proportionate impacts above. The resulting mitigation fee is then reduced from developer expenses to determine reimbursement (see rough example in Section 5.3) 6.3 SUMMARY The project will impact traffic conditions within the study area. However, the impacts of the project can be fully mitigated with the improvements and participation described within this TIS. In addition, recommended improvements should assure the safe and effective operation of study area intersections and arterials through year 2024, as confirmed via the analysis of two forecasting methodologies. No further recommendations are provided by this TIS.