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HomeMy WebLinkAboutTrafficImpactStudyUpdate2_10062021 MARVIN & ASSOCIATES 1300 N. Transtech Way Billings, MT 59102 Mailing Address: P.O. Box 80785 Billings, MT 59108-0785 Phone: 406-655-4550 FAX: 406-655-4991 Page 1 HomeBase Partners 20 North Tracy Avenue Bozeman, MT 59715 9/24/2021 Re: North Central Master Site Plan Traffic Impact Study Update #2 Subsequent to submittal of the Traffic Impact Study (TIS) Update on July 2, 2021, for the proposed North Central Master Site Plan, City of Bozeman Staff review dated August 23, 2021, listed a number of items that needed to be addressed. A development team meeting was conducted with City of Bozeman staff on August 31, 2021, to determine the extent of additional information and analysis that would be required to address the concerns and complete the Master Plans TIS. A written response and summary of the meeting’s discussions was submitted to the City on September 1, 2021. That response document provided clarifications of the analysis methodology and provided a summary of additional information that would be included within this, the second TIS Update. Additional Study Intersections The following intersections surrounding the development site were added to this study update:  Grand Avenue and Mendenhall  Tracy Avenue and Mendenhall Both of these intersections are controlled by stop signs with Mendenhall being the through street. Additional Traffic Volume Counts Attached is a revised Figure 12, which illustrates peak Noon and PM hour traffic volumes at the two Mendenhall intersections in 2017. While a number of additional intersections of local streets were mentioned in the City review. They are low volume streets, which would require additional time to count. Some local intersections have incalculable potential for experiencing site traffic due to limitations inherent in traffic models. As such, it would be nearly impossible to quantify specific impacts. Streets and corridors within the localized grid system will be discussed further within this update. MARVIN & ASSOCIATES 1300 N. Transtech Way Billings, MT 59102 Mailing Address: P.O. Box 80785 Billings, MT 59108-0785 Phone: 406-655-4550 FAX: 406-655-4991 Page 2 Existing Capacity – Additional Intersections Revised Table 10 provides a summary of capacity calculations based on existing conditions in the year 2021 (attached Appendix). In Table 10, it can be seen that the stop controlled approaches at both of the intersections currently operate at level of service (LOS) “C” or better. Trip Generation Trip generation calculation methodology was examined and rechecked relative to the City of Bozeman comments. It was determined that the calculations were reasonable and within the bounds of existing ITE Trip Generation methodology. As such, trip generation tables presented within the first TIS Update are valid. Trip Distribution The City of Bozeman’s review of the original distribution model identified some inconsistences. While percentage distribution on some of these streets were minor, the trip distribution patterns were changed to improve the consistency of the model. Thus, Figure 5 was updated and is attached to this report. The percentage of trips that was shown on Villard Street east of the sites was redirected to Peach Street at its intersection with Tracy Avenue, such that 4% of the trips would access the site on Tracy Avenue rather than Villard. The 1% distribution on Beall Street was distrusted to Mendenhall Avenue and Tracy Avenue. In addition to the Villard and Beal Street adjustments it was determined that approximately 2% of the trips would actually use Grand Avenue to access site parking lots. Figure 5 illustrates the percentage distribution of trips to and from Main Street and Mendenhall Street onto Grand Avenue. Traffic Assignment Traffic assignment in the first update was modified to account for changes made within the trip distribution analysis. The changes in trip distribution affected traffic assignments at three intersections on Mendenhall (Grand Avenue, Willson Avenue, and Tracy Avenue). Beal Street intersections with Willson Avenue and Intersection Int/App Delay LOS Max Q Int/App Delay LOS Max Q Overall na na na Overall na na na NB-Worst 14.1 B 1 NB-Worst 14.0 B 1 Overall na na na Overall na na na NB-Worst 17.5 C 1 NB-Worst 17.1 C 1 Grand Avenue & Mendenhall Street N Tracy Avenue & Mendenhall Street Table 10. Existing Additional Intersections Capacity Calculations Revised 9/8/21 PEAK PM HOURPEAK NOON HOUR MARVIN & ASSOCIATES 1300 N. Transtech Way Billings, MT 59102 Mailing Address: P.O. Box 80785 Billings, MT 59108-0785 Phone: 406-655-4550 FAX: 406-655-4991 Page 3 Tracy Avenue were also affected as was the intersection of Villard and Tracy. Attached updated and revised Figures 6 and 6B are attached and show the new traffic assignment at the intersections. Existing Plus Site Traffic Volume Impacts Attached Figures 13 and 14 are attached and show the traffic volumes that would be associated with existing plus full development traffic. Only 6 of the 12 intersections have changed from the first TIS update. Existing Plus Site Traffic Capacity Revised Table 11 summarizes capacity calculations (see Appendix) completed for existing plus site generated traffic volume conditions. The only intersections that had any measurable changes in capacity were the two intersections on Mendenhall Street. The northbound approach would have an increased delay of 0.1 seconds per vehicle with no change in the LOS or vehicle queues. The intersection of Mendenhall and Tracy Avenue would experience at 2.0 second per vehicle increase in the noon hour and a 0.6 second delay increase in the pm hour. The LOS would remain at LOS “C” in both periods and the maximum queue in the peak noon hour would increase from one to two vehicles. Future Traffic and Capacity Since the update traffic volumes would be less than those in the original TIS, the addition of site traffic to future traffic projection would tend to have less impacts. Because the decrease in site traffic is not substantial, future impacts could be considered to be the same as originally reported. An additional future calculation was completed for the intersection of Tracy Avenue & Mendenhall in the noon hour, and it was determined that the LOS would remain at “C.” Intersection Int/App Delay LOS Max Q Int/App Delay LOS Max Q Overall na na na Overall na na na NB-Worst 14.2 B 1 NB-Worst 14.1 B 1 Overall na na na Overall na na na NB-Worst 19.5 C 2 NB-Worst 17.7 C 1 Table 11. Existing Plus Site Intersections Capacity Calculations Revised 9/8/21 PEAK NOON HOUR PEAK PM HOUR Grand Avenue & Mendenhall Street N Tracy Avenue & Mendenhall Street MARVIN & ASSOCIATES 1300 N. Transtech Way Billings, MT 59102 Mailing Address: P.O. Box 80785 Billings, MT 59108-0785 Phone: 406-655-4550 FAX: 406-655-4991 Page 4 Qualitative Impact Assessment of Operations Impacts to the transportation system are typical measured by distinct methods employing nationally accepted standards, mathematical models, and algorithms. The analysis results in efficiency measures expressed as delay and levels of service. The standard measures of efficiency used within this study indicate that LOS and delay impacts at local intersections will be minimal and without substantial differences from existing conditions. The planned development is located within a completely developed area where the local grid street system has existed for many decades. The North Central Development would have a four block footprint within Downtown Bozeman. As such, there are nine intersections bordering and within the site that are directly associated with access to the development. While trip distribution and traffic assignment external to site can be calculated using conventional methods, calculation of traffic within the site is complicated by on-street parking circulation along with alternative route selection within the site. This study utilized the quickest path method to assign traffic to and from parking facilities based on logical routing. However, this method cannot account for human factors involved in route selection and individuals’ habits. Because of this, traffic assignment within the development cannot be considered 100% accurate. Traffic assignments of zero vehicles on a street or at an intersection may not actually be zero but could be that 1 or 2 vehicles would utilize the facility on certain days of the week. Actual construction of non-residential uses within the development in future years may also change trip generation depending on the ultimate success of the businesses. All of the variables involved in predicting traffic impacts on local streets surrounding a project of this type cannot be stated with a known level of accuracy, and possible impacts cannot be quantified without introducing bias into the analysis. Therefore, the evaluation of local street corridors can only be stated in qualitative terms. New Figure 15 (attached) shows the intersection control at all intersections of local streets within the study area. The following narratives describe the local street corridors, potential impacts, and recommendations for potential impact mitigation: N Willson Avenue – is a through street from Mendenhall Street to Peach Street. The site traffic assignment on this section of Willson Avenue ranges from 659 AWT north of Mendenhall to 288 AWT north of Villard Avenue. The 288 AWT on Willson North of Villard represents a 12% increase over the existing AWT of 2500. This MARVIN & ASSOCIATES 1300 N. Transtech Way Billings, MT 59102 Mailing Address: P.O. Box 80785 Billings, MT 59108-0785 Phone: 406-655-4550 FAX: 406-655-4991 Page 5 AWT volume is well beyond a comfortable level for a local street, but it is far below the ultimate capacity of a two lane street (9000 AWT). The peak pm hour volume on this section of Willson Avenue would be approximately 130 vph or approximately 1 vehicle every 27 seconds on average. The existing street is 30’ wide from Peach Street to Villard Street, 36’ wide from Villard Street to Beall Street, and 38’ wide with variable width boulevards from Beall to Mendenhall. When driving on the corridor at the peak hour, it does not seem to be congested or present any obvious conflicts. Left turns traffic at the intersections are infrequent and the average gap at 27 seconds, delay for left turns is very minor. If future traffic should exceed projections, it would be possible to use some boulevard area to install a center turn lane (if warranted). Various typical sections could be considered to accommodate the center turn lane depending on the need for parking. It may be necessary to eliminate parking on one or both sides of the street to achieve the desired function of the street. Grand Avenue – is stop controlled at every intersection except at its intersection with Short Street, which is uncontrolled. Grand Avenue currently carries no more than 500 AWT and site development would add no more than 28 AWT or approximately 3 vehicles in the peak hours. Grand Avenue does not have curb and gutter along its entire length. At its intersection with Short Street, it appears that there may be some intersection sight distance obstructions. Warrants for stop signs should be evaluated to determine if a stop sign on Short Street is warranted. Tracy Avenue - is a through street from Mendenhall Street to Peach Street. The site traffic assignment on this section of Tracy Avenue ranges from 55 AWT north of Villard to 124 AWT north of Mendenhall Avenue. Existing traffic on Tracy Avenue is approximately 1,600 AWT which indicates that the site would add approximately 8% to existing traffic Volumes. The site development would add approximately 9 vehicles In the peak pm hour. Tracy Avenue is approximately 27’ wide with variable width boulevards along its length. Parking is currently prohibited on the east side of the street. There is only one intermediate intersection between Villard Street and Peach Street on Tracy Avenue and current operations appears to be acceptable. Villard Street - is a through street from N 7th Avenue to Willson Avenue. Villard Street is stop controlled at Willson and Tracy Avenues and right-of way is controlled by yield signs on Villard at Black Avenue. Villard Street is approximately 36’ wide from N 7th Avenue to Black Street. Villard currently carries approximately 500 AWT along its Length. The site development would add approximately 49 AWT within the site area and 123 AWT west of Grand Avenue. This represents MARVIN & ASSOCIATES 1300 N. Transtech Way Billings, MT 59102 Mailing Address: P.O. Box 80785 Billings, MT 59108-0785 Phone: 406-655-4550 FAX: 406-655-4991 Page 6 an increase of 24% over existing volumes between Grand Avenue and N 7th Avenue. The intersections of 4th and 6th Avenues are T intersection that are uncontrolled and stop sign warrants should be reviewed to determine if there is available sight distance at those intersections. It is the authors opinion that the yield signs at the intersection of Villard Street and Black Avenue may be a misapplication of that regulatory sign due to sight distance restrictions and the ability to enter the intersection without stopping. Also, this is the only yield sign on the corridor and is not consistent with control applications at other intersections along the corridor. Beall Street - is a through street from N 7th Avenue to Willson Avenue. Beall Street is stop controlled at Willson and Tracy Avenues and right-of way is uncontrolled at Beall Street and Black Avenue. Beall Street is approximately 36’ wide from N 7th Avenue to Black Street with the exception of the section between Willson and Tracy, where it is approximately 44’ wide. Beall Street currently carries approximately 500 AWT along its Length. The site development would add approximately 27 AWT west of Willson Avenue and approximately 255 AWT between Willson and Tracy. A stop sign warrant should be explored at its intersection with Black Avenue. Lamme Street - is a through street from N 7th Avenue to Willson Avenue. Lamme Street is stop controlled at Willson and Tracy Avenues and right-of way is uncontrolled at Beall Street and Black Avenue. Lamme Street is approximately 32’ wide from N 7th Avenue to Black Street. At its intersection with Tracy Avenue , the continuation of Lamme to the east is offset to the north by a distance of approximately 55 feet. The directional offset allows left-turning traffic on Tracy Avenue without overlapping vehicle paths and should operate safely provided that sight distance at the intersection is maintained. Lamme Street currently carries approximately 1,000 AWT along its Length. The site development would add between 10 and 27 AWT, which is between a 1% an 2% increase. It is not anticipated that there would be any impacts that would detract from the current nature of the street. MARVIN & ASSOCIATES 1300 N. Transtech Way Billings, MT 59102 Mailing Address: P.O. Box 80785 Billings, MT 59108-0785 Phone: 406-655-4550 FAX: 406-655-4991 Page 7 CONCLUSIONS & RECOMMENDATIONS The redistribution of trips and reassignment of traffic had very minor effects on the TIS analysis described in the first TIS update. No impacts were found at the additional intersections that were added to the TIS study analysis. Therefore, recommendations made within the original TIS for the North Central Development Master Plan would still be applicable. If additional information concerning the TIS update is required, feel free to contact me. Robert R. Marvin, P.E., P.T.O.E.