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HomeMy WebLinkAbout15 - Traffic Impact Study - The Springs LivingTRAFFIC IMPACT STUDY for The Springs Living at Bozeman Bozeman, Montana Prepared for The Springs Living Prepared by MARVIN & ASSOCIATES 1300 North Transtech Way Billings, MT 59102 M a r c h 5 , 2 0 1 5 TRAFFIC IMPACT STUDY for The Springs Living at Bozeman Bozeman, Montana Prepared for The Springs Living Prepared by MARVIN & ASSOCIATES 1300 North Transtech Way B i l l i n g s , M T 5 9 1 0 2 March 5, 2015 P.T.O.E. #259 i TABLE OF CONTENTS P A G E INTRODUCTION 1 SITE LOCATION & DESCRIPTION 2 EXISTING CONDITIONS 2 Streets & Intersections 2 T r a f f i c V o l u m e s 4 Speeds 6 Capacity 6 TRIP GENERATION 7 T R I P D I S T R I B U T I O N 8 T R A F F I C A S S I G N M E N T 1 0 T R A F F I C I M P A C T S 1 2 E x i s t i n g T r a f f i c V o l u m e s 1 2 Capacity 14 Safety- Auxiliary Turn Lane Warrants 15 F U T U R E C O N D I T I O N S 1 5 T r a f f i c V o l u m e s 1 5 Future Capacity 17 Future Safety Conditions 17 MODIFIATIONS TO CITY GUIDELINES 22 R E C O M M E N D A T I O N S 2 4 APPENDIX A – TRAFFIC VOLUMES APPENDIX B – SPEED STATISTICS APPENDIX C - CAPACITY CALCULATIONS APPENDIX D - LEFT TURN LANE WARRANTS ii LIST OF TABLES P A G E Table 1. Existing Peak Hour Capacity Analysis Summary 6 Table 2. The Springs Living Trip Generation Summary 7 Table 3. Existing Plus Development Site Traffic Peak Hour Capacity Analysis Summary 14 Table 4. Future (2025) Peak PM Hour Capacity Analysis Summary 17 LIST OF FIGURES P A G E Figure 1. Site Location Map 3 Figure 2. Existing 2015 Traffic Volumes 5 Figure 3. Directional Distribution of Site Trips 9 Figure 4. Site Generated Traffic Assignment 11 Figure 5. Existing Plus Site Generated Traffic Volumes 13 Figure 6. Future Traffic at Site Accesses 16 Figure 7. Maximum Vehicle Queues & Available Sight Distance 18 The Springs Living at Bozeman Traffic Impact Study The Springs Living at Bozeman TIS Page 1 INTRODUCTION Marvin & Associates was retained by “The Springs Living” to provide a Traffic Impact Study (TIS) for The Springs Living at Bozeman development. This report summarizes the findings of the TIS. The purpose of the TIS is to determine whether this development would impact the surrounding street system and related intersections. During initial discussions with the City of Bozeman Public Work Department we were informed that the potential impacts of greatest concern would be the four intersections of Cattamount Street and Catron Street with both Davis Lane and N 27th Avenue. The proposed development site access to Catron Street would not meet the minimum separation distance from the intersection and the N 27th Avenue access would not meet separation distance for adjacent driveways required by the City of Bozeman. Therefore, this study provides specific information addressing modification of the guidelines according to Ordinance #1755. Therefore, the main emphasis of this study is related to impact at the four intersections and modifications to the guidelines for access locations. Having reviewed the proposed land use development plan and existing site conditions, Marvin & Associates collected traffic data, completed an analysis of existing conditions, addressed trip generation, trip distribution and traffic assignment, evaluated capacity impacts, and provided information related to access standard modifications. The study methodology and analysis procedures used in this study employed the most contemporary of analysis techniques, referencing only nationally accepted guidelines in the areas of site development and transportation impact assessment. Recommendations made within this report are based upon those guidelines and the professional judgment of the author. The Springs Living at Bozeman TIS Page 2 SITE LOCATION & DESCRIPTION The Springs Living development is located in the southeast corner of N. 27th Avenue and Catron Street. The property is bordered on the south by vacant land and on the east by a Target store. Figure 1 illustrates the proposed layout of The Springs Living. The three story building would occupy the corner of Catron Street and N 27th Street with the building facing both adjacent streets and parking would be provided on the east and south sides of the building. The building would be used as a retirement community accommodating independent and assisted living rooms along with memory care units. The building would also incorporate many dining, recreation, health, and fitness facilities for it residents. According to the development plan they would be 78 independent living units, 68 assisted living units, and 24 memory care units for a total of 170 rooms. The access to North 27th Avenue would be located approximately 465 feet south of the Catron Street - N 27th Avenue intersection while the Catron Street access would be located approximately 308 feet east of that intersection. The minimum distance required by City of Bozeman Ordinance is 330 feet on collector streets. Thus, the Catron Street access would require modifications from the guidelines. In addition, there are two existing accesses on N 27th that will also require modifications to the standard driveway separation distances. EXISTING CONDITIONS Streets & Intersections Although various area streets and intersections could have the potential for impacts, this study’s primary focus is on the four intersections involving Davis Lane, N 27th Avenue, Catron Street and Cattamount Street. Impacts also include the development’s accesses to North 27th Avenue and Catron Street. The Springs Living at Bozeman TIS Page 3 The Springs Living at Bozeman TIS Page 4 Davis Lane is a paved street with curb and gutter on both side and carries two lanes of traffic. It extends from Oak Street to Valley Center Road north of the study area. North 27th Avenue is currently improved with curb & gutter and has a paved surface from Cattail Street to Valley Center Road. It carries two traffic lanes with bikes lanes and parking on the west side. Catron Street and Cattamount Streets are both full width streets with curb & gutter and bicycle/pedestrian facilities. Cattamount Street connects N 27th Street and Davis Lane with plans for a future connection to the east at Valley Center Road. Catron Street extends between Valley Center Road and Davis Lane. Traffic Volumes Twenty-four hour automatic traffic counts were taken in October of 2014 on Catron Street and in February 2015 on N 27th Street and Davis Lane. The counts provided hourly variations, which were used to determine peak hours and provide base volumes for turning movement projections. Summaries of the counts can be found be Appendix "A" of this report. The highest hourly volumes were found to occur between 4:30 and 5:30 p.m. The peak pm hour volumes were between 10.0% and 10.7% of the average weekday traffic (AWT) on these streets. Figure 2, on the following page, presents existing (2015) pm peak hour turning movement volumes that were taken in February 2015 at the four intersections within the study area, along with AWT volumes. Some of the street segment volumes represent actual counts while others were calculated from turning movement counts. Pedestrian and bicycle activity was found to be minimal at most of the study intersections and therefore was not indicated on the turning movement diagrams. Pedestrian and bicycle traffic volumes, based on peak hour manual counts, was found to be less than 1% of all traffic. Heavy truck traffic on these local streets was also less than 1% of all traffic. The percentage of school bus traffic during the pm counting period was approximately 2% on N 27th and 2% on Davis Lane. The Springs Living at Bozeman TIS Page 5 The Springs Living at Bozeman TIS Page 6 Speeds Appendix B contains speed statistics for Catron Street N 27th Avenue and Davis Lane based on electronic traffic counter data. It was determine that the 85th % speed on Catron Street is approximately 27 mph. On N 27th Avenue the 85th % speed is approximately 32 mph and it is approximately 41 mph on Davis Lane. Capacity PM peak hour capacity calculations were completed for each of the 4 study intersections (see Appendix C for calculations). The unsignalized intersection capacities were calculated using HCS 2010 software. Results of the calculations can be found in Table 1. Measures of effectiveness (MOEs) in Table 1 include average delay, level of service (LOS), and volume-to-capacity (v/c) ratio. Table 1. Existing Peak Hour Capacity Analysis Summary Control Delay (s/veh) LOS V/C Ratio Queue Length (95%) Control Delay (s/veh) LOS V/C Ratio Queue Length (95%) Control Delay (s/veh) LOS V/C Ratio Queue Length (95%) Control Delay (s/veh) LOS V/C Ratio Queue Length (95%) LTR 12.1 B 0.19 1 B 01 0.00 0.06 LR B Davis Lane & Cattamount Street 7.6 10.2 A Movement Group LT 0 Davis Lane & Catron Street A 0.01 0.28 LR 7.7 12.4 Movement Group LT 2 2 LR LTR 12.4 1 A 7.4 7.5 A 0.03 0 WB 9.6 0.12 0.30 B EB N. 27th Avenue & Cattamount Street Movement Group 0.04 0 LT A Movement Group LTR 7.3 Intersection MOE NB LTR SB N. 27th Avenue & Catron Street A 0.02 0 The capacity calculations revealed that all intersection approaches and individual approach movements currently operate at or above an acceptable LOS “B” under pm peak hour conditions. The westbound approach on Catron Street at N 27th Street has the highest delay at 12.8 seconds per vehicle and a v/c ratio of 0.30. However, it currently operates at LOS “B” during the peak pm hour. The maximum vehicular queue for that approach is approximately 2 vehicles. The Springs Living at Bozeman TIS Page 7 TRIP GENERATION Table 2 presents trip generation estimates for The Springs Living development. Trip generation rates and resulting trips are shown for the average weekday and for the am and pm peak hours. The rates were taken from ITE’s Trip Generation Report, 9th Edition. The ITE report has a number of land uses that have certain elements of the proposed facility, but only ITE Code 255 “Continuing Care Retirement Community” has most of the characteristics that would be associated with this development. The ITE report also indicates that trip rates based on the number of beds rather than the number of living units is more aligned with rate data. Therefore, the projections contained in Table 2 were based on approximately 207 beds contained within the 170 resident units. Table 2. The Springs Living Trip Generation Summary No. of Rate Total Total Total Land Use Units Units Rate Trips Rate Trips Enter Exit Rate Trips Enter Exit 207 *Beds 1 657 2 48 31 17 3 86 34 52 *ITE Occupied Units 1 - T = 2.32(X)+176.28 2 - T = 0.13(X)+21.28 (65% enter) 3 - T = 0.13(X)+59.19 (40% enter) Peak AM HourAverage Weekday Peak PM Hour Code 255 Continuing Care Retirement Community The gross projected average weekday trips (AWT) for The Springs Living would total 657 AWT. During the p.m. peak period, total development trips would be 86, with approximately 34 entering and 52 exiting the site. In the a.m. hour, there would be 48 trips with 31 entering and 17 exiting the site. Not all of the generated trips would be vehicular, nor would all of the trips result in new traffic on the street system. A segment of new trips could be attributed to pedestrians and bicycle traffic because of the proximity to large commercial and office trip attractors, but for the purposes of this analysis, none of the trips were assigned to alternative transportation modes. The Springs Living at Bozeman TIS Page 8 The number of external vehicle trips as presented in Table 2 can be further categorized as primary purpose, diverted link, or passerby purpose trips. Primary purpose trips are trips for which the development is a primary destination from any particular origin. Diverted link trips are trips made to a development as a secondary destination that must be diverted from a path between the origin and primary destination. Passerby trips are also trips made to a development as a secondary destination, but without a diversion from the primary trip path (i.e., a stop on the way home from work). The ITE Trip Generation Report provides methods for estimating passerby trips for a variety of facilities. For this development it can be assumed that there will be no passerby trips. TRIP DISTRIBUTION There are various methods available for determining the directional distribution of trips to and from site developments. For developments within a large urbanized area, the task is best accomplished through the creation of a computerized transportation model of the urban street system, which includes the proposed development changes. When the creation of a model is not feasible, reliable estimates can be made by calculating the distribution of existing traffic volumes on the surrounding street system. Figure 3, on the following page, shows a graphical summary of the directional trip distribution, which is based on composite methods of existing traffic flow and land use distribution patterns. The method used existing directional traffic distribution and adjustments were made to account for adjacent developments that would not typically be associated with trip attractions to this particular land use. Generally, 15% of the trips would be directed to the north and west, with 51% of the trips directed to the south and east. Approximately 34% of the trips would be directed to and from the south and west. The Springs Living at Bozeman TIS Page 9 The Springs Living at Bozeman TIS Page 10 The directional distribution of trips would have multiple paths choices within the immediate area. A travel time analysis on a number of paths to and from the main arterials was completed to determine the relative distribution of trips within the area of potential impact, as shown in Figure 3. TRAFFIC ASSIGNMENT The assignment of development site traffic to the street system and site access points is dependent upon several factors. Two such factors are external directional distribution and localized operational site conditions. The combined calculation of demand and least time accessibility are then used to estimate likely movement volumes at each individual access point. Turning movements at each access point can then be calculated through the application of primary trip distributions to full development vehicular trip generation totals. In the case of The Springs Living, there are a total of two different access points, each on different streets. Individual demand at each access is dependent upon travel time and the relative location of land uses within the site. Figure 4, on the following page, illustrates the results of average weekday and pm peak hour, site-generated traffic assignment for The Springs Living. Peak pm hour traffic assignments at each of the individual approaches are also detailed in Figure 4. The Springs Living at Bozeman TIS Page 11 The Springs Living at Bozeman TIS Page 12 TRAFFIC IMPACTS Existing Traffic Volumes Traffic volume impacts for site developments can often be quantified by determining the change in traffic volumes expected at various points within the surrounding network of streets. Site traffic assignments give an indication of what volume of traffic could potentially be added to the street system during the average weekday (AWT). The percent change in AWT can be used to identify general locations where impacts could be significant, but it is the change in traffic during peak periods that provide specific information on the type and location of impacts that could potentially occur. In almost all cases, it is very difficult to determine AWT on any section of street to within 10% accuracy. Thus, impact analyses on streets with relative percentage increases less than 10% are not normally considered critical. Figure 5, on the following page, illustrates the associated traffic volume impacts related to full development site traffic added to existing background traffic on the surrounding street system. Figure 5 also shows existing volumes plus site traffic on each street segment and the relative percentage increases over existing AWTs. The only significant increases in AWT (greater than 10%) would occur along N 27th Avenue south of the development site. The Springs Living at Bozeman TIS Page 13 The Springs Living at Bozeman TIS Page 14 Capacity Table 3, below, summarizes capacity analysis results (see Appendix C) for existing plus site generated traffic at each of the potentially impacted intersections. The calculations indicated that there would not be any significant capacity impacts resulting from the addition of site generated traffic. The intersection of N 27th Avenue and Catron Street would still operate with a LOS “B” for the eastbound and westbound approaches, with no substantial increase in delay. The proposed Catron Street site access would operate at LOS B and the N 27th Avenue site access would operate at LOS A. The capacity impacts indicated in Table 3 provide an indication of how these intersections would operate if the development existed today so that it can be determined where mitigating measures should be applied. Table 3. Existing Plus Development SiteTraffic Peak Hour Capacity Analysis Summary Control Delay (s/veh) LOS V/C Ratio Queue Length (95%) Control Delay (s/veh) LOS V/C Ratio Queue Length (95%) Control Delay (s/veh) LOS V/C Ratio Queue Length (95%) Control Delay (s/veh) LOS V/C Ratio Queue Length (95%) Control Delay (s/veh) LOS V/C Ratio Queue Length (95%) Control Delay (s/veh) LOS V/C Ratio Queue Length (95%) LT LR LTR EB B Movement Group 0.01 0.06 A 0 0.31 2 0.01 Davis Lane & Cattamount Street 7.6 10.2 ABDavis Lane & Catron Street 7.8 Movement Group LTR LTR Intersection MOE NB SB 01 LRLT 12.8 AA N. 27th Avenue & Catron Street Movement Group N. 27th Avenue & Cattamount Street Movement Group 7.4 9.7 LR WB LTR LT 1 0.05 0.12 0 7.4 7.5 13.2 AA B 12.6 B 2 0.02 0.03 0.34 00 0.21 1 Movement Group LT LR N. 27th Avenue & Site Access 7.5 9.8 AA 0.00 0.06 01 Movement Group LR LT Catron Street & Site Access 13.1 8.1 BA 0.08 0.15 11 The Springs Living at Bozeman TIS Page 15 Safety – Auxiliary Turn Lane Warrants Auxiliary turn lane warrants were evaluated for existing plus site generated traffic conditions (see Appendix D). It was found that none of the intersections or site accesses would have sufficient traffic to warrant turn lane considerations. FUTURE CONDITIONS Traffic Volumes Growth in background traffic is dependent upon continued subdivision development in the area. Traffic counts were taken in 2007 on Catron Street and on N. 27th Avenue. It appears that in the past seven years, traffic has increased on N. 27th Street by 40% on N. 27th Avenue and by 50% on Catron Street. In an examination of available land remaining for development within the impact area, it was determined that areas accessed by Catron Street are approximately 60% to 70% developed, while areas that could be accessed by N 27th Avenue are approximately 20% developed. If historic growth rates were to occur in the next 10 years it is estimated that traffic on Catron Street would increase by approximately 50% and traffic on N 27th would increase by approximately 100%. It should also be noted that a future connection of Cattamount Street to Valley Center Road would provide an alternate route to N 27th from the east and north, which would essentially limit the ultimate traffic demand on Catron Street. Figure 6 indicates traffic projections on both of these streets using the above noted future growth assumptions. Peak pm hour traffic at the intersection of Catron Street and N 27th Avenue along with peak pm hour traffic at both of the site accesses are shown. The traffic volume projections at these intersections are used to determine the operational conditions that could occur within the foreseeable future. The Springs Living at Bozeman TIS Page 16 The Springs Living at Bozeman TIS Page 17 Future Capacity Table 4 summarizes the year 2025 capacity calculations associated with the projected traffic volumes. It can be seen that the minimum LOS at the intersection of Catron Street and N 27th Avenue would be reduced to “C” on the east and west approaches and the vehicle queues on the westbound approach would increase to 5 vehicles from 2 vehicles that currently exists. The N 27th Avenue site access would operate at LOS “B” while the Catron Street site access would operate at LOS C. This indicates that both site accesses would operate efficiently under future traffic loadings. Table 4. Future (2025) Peak PM Hour Capacity Analysis Summary Control Delay (s/veh) LOS V/C Ratio Queue Length (95%) Control Delay (s/veh) LOS V/C Ratio Queue Length (95%) Control Delay (s/veh) LOS V/C Ratio Queue Length (95%) Intersection MOE NB SB EB WB Movement Group LTR LTR LTR LTR N. 27th Avenue & Catron Street 7.5 7.7 17.2 23.8 AACC 0.03 0.05 0.40 0.66 012 5 Movement Group LT LR N. 27th Avenue & Site Access 7.7 10.8 AB 8.7 0.00 0.08 01 0.25 Movement Group LR LT Catron Street & Site Access 18.3 11 CA 0.13 Future Safety Conditions The primary consideration for safety is available sight distance at intersections and driveway accesses. In this case there are no permanent physical barriers that would limit the line of sight for motorists entering or exiting the site accesses. However, sight distance can also be obscured by mobile or temporary conditions such as vehicular queues that could block the line of sight for vehicles entering or exiting driveway approaches. Figure 7, on the following page was developed to illustrate the extent of maximum vehicular queues that could impact safe operations at the proposed site accesses. The Springs Living at Bozeman TIS Page 18 The Springs Living at Bozeman TIS Page 19 The Catron Street access would have two access movements with potential for conflicts. The exit maneuver would require an adequate line of sight both east and west. The unobstructed line of sight to the east would be approximately 600’ while the line of sight to the west would be limited to 302’ if the maximum calculated number of vehicles were queued at the Catron Street and N 27th Street intersection. AASHTO guidelines provide design values for the minimum stopping and intersection sight distances. Since the 85th% speed on Catron Street was measured to be approximately 27 mph, the AASHTO minimum stopping sight distance would be approximately 200’ at 30 mph. The sight distance required for a vehicle to make a left turn from the access without impeding traffic flow would be approximately 330’ at 30 mph. The sight distance required to make a right turn from the access would be approximately 290’ at 30 mph. Figure 7 indicates that there would be approximately 302’ of available sight distance when the maximum vehicular queue is present on the westbound intersection approach. It would appear that there would be less sight distance available for the left-turn than the AASHTO intersection guidelines suggest for facilities with 30 mph design speeds. However, there are a number of elements that need to be considered. Speeds on Catron Street are actually less than 30 mph and if calculated at 27 mph the required sight distance would be close to 300’. Secondly, vehicles approaching the site access from the west would not be traveling anywhere near 30 mph at a point 302’ west of the access since any eastbound vehicle would have entered the adjacent intersection from a stop or by turning from N 27th Avenue. At that point, vehicles would be traveling at no more than 15 mph and in the processing of accelerating. Thirdly, the line of sight was measured from a point where the motorist’s eye position is located when the vehicle is as close to the street as possible. At any position 2 to 3 feet back into the site would provide unlimited sight distance to the intersection. In this case, stopping sight distance would be the controlling measurement that would ensure safe operations and thus, sufficient sight distance would be available. The Springs Living at Bozeman TIS Page 20 The other site access movement on Catron Street that requires a clear line of sight would be the westbound left-turn movement into the access. Figure 7 indicates that the sight distance that would be available during peak future traffic conditions is approximately 280 feet. AASHTO guidelines indicate that the minimum sight distance for that maneuver would be 245’ at a design speed of 30 mph. Since the available sight distance is more than the minimum, it can be assumed that the left-turn movement into the site can be made safely in the future. The N 27th Avenue access would provide relatively unlimited sight distance based on the tangent roadway alignment and the absence of permanent sight obstructions. Unlike the Catron Street access, mobile and temporary sight obstructions do not involve conditions at the intersection of Catron Street and N 27th Avenue. Two accesses on the opposite side of N 27th Avenue flank the proposed site access and there is potential for vehicles turning left into those driveways to block the line of sight of oncoming traffic. The 85th% speed on N 27th Avenue was measured at 32 mph, which is in the same range as the 30 mph design speeds relative to the AASHTO guidelines. Thus, left turns from the site access should have 330’ of sight distance, right turns from the access should have 290’, and the stopping sight distance should be 200’. Sight distance for left–turns into the site access would not be impeded by vehicle movements into or out of adjacent driveways. Since the two driveways on the west side of N 27th Avenue would access apartment buildings (currently under construction) that would have 64 units, the total trip generation for those apartments would be less than 400 trips on the average weekday. During the peak pm hour each of the two accesses would have approximately 20 trips with 13 vehicle entering. With similar trip distribution The Springs Living at Bozeman TIS Page 21 applied to the apartments, the maximum number of left-turn movements into each approach would be approximately 6 vehicles or 1 vehicle every 10 minutes. This is the same volume of traffic that would enter the study site in the southbound direction from N 27th Avenue. Capacity calculations for that movement resulted in 7.7 second delay and maximum vehicle queues less than 0.1 vehicles. Thus, any mobile sight obstructions would be rare, but possible. For this situation another measure of sight distance is necessary to determine if the rare and fleeting sight obstructions have the potential to create safety concerns. Figure 7 illustrates conditions where a left-turning vehicle can shadow on-coming vehicles to an extent where a driver at an adjacent approach cannot see the trailing vehicle and makes a decision to enter the roadway. Figure 7 shows the “Shadow Zones” where a trailing vehicle can be hidden. The shadow zone lengths were measured and converted into time equivalents based on the 85th% speeds. In, this case the shadow zones for both cases were determined to be 0.8 seconds in length. All of the AASHTO sight distance criteria is based upon time and speed calculations that incorporate 2.5 seconds for perception and reaction time. Since the shadow zone lengths are 0.8 seconds, they are well below the perception/reaction time and they are one half of the standard 1.5 seconds perception time. Thus, it would be extremely unlikely that the average driver would miss seeing vehicles when they pass thru the shadow zone. From this analysis it can be concluded that would be no future sight distance and safety concerns associated with the N 27th Avenue site access relative to the adjacent driveway accesses. The Springs Living at Bozeman TIS Page 22 MODIFICATION TO CITY GUIDELINES City of Bozeman ordinances require specific separation distances between driveways and intersections as well as separation between adjacent driveways based on varied street classifications. Catron Street and N 27th Avenue are both Collector streets and the required separation between a driveway and street intersection is 330’ from the inside edge of the driveway to the nearest right-of- way (R/W) line for the intersecting street. The required separation distance between driveways on a Collector Street is 150’ from the inside edge of adjacent driveways. Modifications from the ordinance requirements for commercial developments can be considered by the City of Bozeman by requesting the modifications contained in Article H of Ordinance 1755 Item # 3 and submitting the following information prepared by a certified professional engineer. a. Traffic volumes b. Turning movements c. Traffic controls d. Site design e. Sight distances f. Location and alignment if other access points All of the above information is contained in the text and figures contained within this report. In addition to this information, the following narratives provide additional information with regard to the extent of modifications and logical reasoning that should be considered when deciding whether to approve the modifications. The Springs Living at Bozeman TIS Page 23 The inside edge of the proposed site access on Catron Street would be located approximately 308’ (along the Catron Street alignment) from the eastern R/W line on N 27th Avenue and would required an approved modification to the guidelines since it would be 22’, short of the standard. There is also another driveway adjacent to and east of the Catron Street site access. The approximate separation distance between that access and the proposed site access is 158’ which exceeds the City of Bozeman requirements. The R/W line at the intersection of Catron Street and N 27th Avenue is approximately 465’ from the inside edge of the proposed site approach to N 27th Avenue, which exceeds the City of Bozeman standard. However, the N 27th Avenue site access is located between two driveways on the west side of the street and the separation distance from the inside edge of the north driveway is approximately 144’, which is 6’ short of the guideline. The separation between the inside edge of the southern driveway is approximately 135’, which is 15’ short of the guideline. Therefore the N 27th Avenue access would require relaxation of the guidelines. The relative variations from the guidelines for the three modifications requested range between 4% and 10% of the guideline distances. In considering relaxation of those guidelines, it should be remembered that the guidelines were actually derived from conditions incorporating average geometrics conditions, speeds, and traffic flows that are typically associated with local, collector, and arterial streets. Analysis of safety and operations at for specific circumstances, such as presented herein, are more applicable than those that were derived with the objective of covering a wide range of conditions. The Springs Living at Bozeman TIS Page 24 Any alternative that would involve relocating the site access on N 27th Avenue to align with an existing driveway on the opposite side of the road would be impossible, given the development plan and function. Even if it were possible, it would not be entirely desirable from a safety standpoint. Opposite driveways would function as a four legged intersection. Four legged intersections have 32 points of conflict, whereas T-intersections only have 6 conflict points. That is why many agencies convert four legged intersections to offset T-intersections as a safety improvement measure. As long as the offset avoids overlapping, opposing left-turn movements, two offset T-intersections operate more safely than a single four legged intersection. RECOMMENDATIONS The development of The Springs Living would generate approximately 657 additional trips on the average weekday and 86 during the typical pm peak hour. Although traffic volume increases would be likely on adjacent streets and intersections, none of those streets or intersections would be impacted by the additional traffic volumes generated by this development. Therefore, the development could be constructed, as planned, without substantially impacting existing traffic operations. The two proposed site accesses do not exactly meet the City of Bozeman ordinance for separation between adjacent driveways and intersections. For the site plan to be approved, the developer is requesting a relaxation or modification to the separation guidelines. An extensive analysis of the operations and safety of the proposed access locations was completed and summarized within this report and it is recommended that the separation modifications be granted for this site development.