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HomeMy WebLinkAboutTraffic Impact Study_Part 2B 01 16 2018 memo Page 1 TO:Bob Murray, P.E. City of Bozeman FROM:Bill White James Nickelson, P.E. DATE: May 12, 2015 JOB NO.: 5352.003 RE: The Lakes at Valley West, Supplemental TIS Analysis #2 CC: Greg Stratton Urgent For Review Please Comment Please Reply For Your Use This memorandum summarizes supplemental analyses #2 provided in support of the Lakes at Valley West Traffic Impact Study (TIS) submitted to the City of Bozeman in February 2015. This analysis was developed to review the benefit potential of a basic signal system for the Cottonwood Road/Durston Road intersection and to advance discussion and support for an intermediate or temporary four-way stop at the Laurel Parkway/Durston Road intersection. 1. BASIC SIGNAL SYSTEM The Lakes at Valley West TIS confirms the Cottonwood Road/Durston Road intersection currently functions at LOS D, identified as a preexisting deficiency below the LOS C operations/capacity thresholds identified in Sec. 38.24.060 of City of Bozeman “Unified Development Code”. Traffic operations were anticipated to degrade to LOS F by year 2024, as determined based upon two forecasting alternatives that: 1) stress a growth of through traffic on Durston Road via higher baseline growth rates versus 2) stress growth of turning movements through the inclusion/application of concurrent development growth (i.e. pipeline project development within the study area). The conclusion of the TIS was that a traffic signal or roundabout would be needed to address LOS issues at the intersection by year 2024. In support of this supposition, the TIS advanced an analysis that reviewed traffic operations at the intersection with assumption of an actuated signal system that includes eastbound and westbound left-turn lanes with designated signal luminaries, per current City of Bozeman Capital Improvement objectives. Such an improvement would result primarily in LOS A/B traffic operations with less than 11 seconds of control delay being noted through year 2024, as based on a review of both forecast methodologies. The City requested an analysis of an interim signal system at the intersection, as based on current geometries. This “basic” signal system would be constructed with vehicle detection promoted by video or pavement “pucks” with all through and turn movements performed through single lane intersection approaches (i.e. the intersection of two lane roadways with no turn lanes) and permissive, single approach luminaries. The analyses was performed based on AM and PM peak hour alternative traffic volumes highlighted in Figure 9 and 10 for the “growth” scenario and Figure 15 and 16 for the “pipeline” scenario of the TIS, with LOS and control delay results as follows. TheLakesatValleyWest,SupplementalTISAnalysis#2 Page 2 As shown, the intersection would function within the LOS A/B range by year 2024 with less than 15 seconds of control delay determined between forecast scenarios. This indicates the basic signal system would promote adequate LOS, despite the difference in forecasts between the growth scenario (with higher through volumes on Durston) versus pipeline scenario (with higher turn movements to/from Cottonwood) forecast scenarios. The City requested furthermore that the analysis be extended to year 2034 to assess the longevity of the basic signal system proposal. Forecasts were developed as described by the TIS, with the exception that baseline growth rates, 3 percent annual for the “growth” scenario and “1 percent annual for the “pipeline” scenario were extended an additional 10 years. These forecasts can be obtained upon request. LOS analyses were revised through year 2034, with the results summarized as follows. As shown, the intersection would function within the LOS B range during the peak hours, as based on pipeline project scenario. However, a LOS D is projected during both peak hours, as based on the growth scenario, which is below the City LOS C standards. This means the growth in through traffic will have a substantial impact on the ability of a basic signal system to maintain adequate traffic operations between year 2024 and year 2034. The conclusion from this analysis is that a basic signal system can be developed at the intersection and should maintain LOS for a number of years, but ultimately lane improvements would be needed to maintain long range LOS. 2. FOUR WAY STOP Supplemental analysis #1 reviewed the LOS benefits of a four way stop at the Laurel Parkway/Durston Road intersection as an interim improvement until the extension of roadways such as Oak Street, Annie Street, and possibly Sherwood Way to Cottonwood Road can promoted; rerouting traffic from the intersection and therefore reducing southbound left-turns from the intersection (which is the critical movement most impacting LOS). The interim improvement would promote LOS C operations through year 2024 during the peak hours, as determined based on a review of the alternative traffic volumes highlighted in Figure 9 and 10 for the “growth” scenario and Figure 15 and 16 for the “pipeline” scenario of the TIS. City of Bozeman staff requested further information and support for a four way or all way stop at the intersection, even as an interim measure. Justification for an all way stop is provided by the Manual on Uniform Traffic Control Devices (MUTCD) by the Federal Highway Administration. The current, year 2009 version of the MUTCD indicates the following information can be used in support of an all way stop. TheLakesatValleyWest,SupplementalTISAnalysis#2 Page 3 Section 2B.07 Multi-Way Stop Applications Support: 01 Multi-way stop control can be useful as a safety measure at intersections if certain traffic conditions exist. Safety concerns associated with multi-way stops include pedestrians, bicyclists, and all road users expecting other road users to stop. Multi-way stop control is used where the volume of traffic on the intersecting roads is approximately equal. 02 The restrictions on the use of STOP signs described in Section 2B.04 also apply to multi-way stop applications. Guidance: 03 The decision to install multi-way stop control should be based on an engineering study. 04 The following criteria should be considered in the engineering study for a multi-way STOP sign installation: A. Where traffic control signals are justified, the multi-way stop is an interim measure that can be installed quickly to control traffic while arrangements are being made for the installation of the traffic control signal. B. Five or more reported crashes in a 12-month period that are susceptible to correction by a multi-way stop installation. Such crashes include right-turn and left-turn collisions as well as right-angle collisions. C. Minimum volumes: 1. The vehicular volume entering the intersection from the major street approaches (total of both approaches) averages at least 300 vehicles per hour for any 8 hours of an average day; and 2. The combined vehicular, pedestrian, and bicycle volume entering the intersection from the minor street approaches (total of both approaches) averages at least 200 units per hour for the same 8 hours, with an average delay to minor-street vehicular traffic of at least 30 seconds per vehicle during the highest hour; but 3. If the 85th-percentile approach speed of the major-street traffic exceeds 40 mph, the minimum vehicular volume warrants are 70 percent of the values provided in Items 1 and 2. D. Where no single criterion is satisfied, but where Criteria B, C.1, and C.2 are all satisfied to 80 percent of the minimum values. Criterion C.3 is excluded from this condition. Option: 05 Other criteria that may be considered in an engineering study include: A. The need to control left-turn conflicts; B. The need to control vehicle/pedestrian conflicts near locations that generate high pedestrian volumes; C. Locations where a road user, after stopping, cannot see conflicting traffic and is not able to negotiate the intersection unless conflicting cross traffic is also required to stop; and D. An intersection of two residential neighborhood collectors (through) streets of similar design and operating characteristics where multi-way stop control would improve traffic operational characteristics of the intersection. A review of MUTCD guidelines was performed based on available traffic data for the intersection (highlighted in 0.4 and 0.5). As data was limited and/or incomplete, the review is limited based on the available data . However, as the all way stop is proposed an interim improvement, this should be sufficient in supporting a decision for the improvement. Applicable data includes discussion on traffic volumes, bicycle and pedestrian safety, left turn conflicts, and street classification considerations. A summary of discussion is as follows for applicable guidelines/data. 0.4 A. A traffic signal is not a preferred improvement at Laurel Parkway/Durston Road; thus, this guide is not directly applicable for the intersection. However, a similarity is as the all-way stop is recommended as an interim improvement until future east-west roadway connections can be promoted within Bozeman; specifically the extension of roadways such as Oak Street, Annie Street, and possibly Sherwood Way to Cottonwood Road. These extensions will allow traffic to divert away from the Laurel Parkway/Durston Road intersection and travel via other routes to make turn movements to/from Durston Road via the signalized Cottonwood Road intersection in the future. This will improve LOS as traffic is reduced from the critical southbound left-turn TheLakesatValleyWest,SupplementalTISAnalysis#2 Page 4 movement at the intersection. It is therefore envisioned the all-way stop could be reduced as these roadway extensions are complete. Thus, although this MUTCD guideline is not directly applicable, there are some similarities that would provide some rational or justification via engineering reasoning. 0.4 B. Collision histories provided by the City of Bozeman indicate that less than one collision per year has been noted for the Laurel Parkway/Durston Road intersection. With the introduction of the fourth/south leg and as a result of increased traffic volumes projected in the future, the potential for collisions will increase. However, this is not sufficient support to suggest this particular guideline could be used in support of the all way stop. 0.4 C. There are three sets of criteria associated with this guideline. The first indicates that major street volumes entering the intersection must be 300 vehicles per hour for 8 hours of a typical weekday to meet the guide. The second indicates minor street volumes, including the combination of vehicles, pedestrians, and bicycles, must be 200 per hour for 8 hours concurrently of the weekday to fulfill the guideline with a peak/one hour delay of 30 seconds. The final indicates 70 percent of volume these respective criteria can be used, 225 major street vehicles and a combination of 140 hourly vehicles, pedestrians, and bikes on the minor approach, can be used for streets with an 85th percentile speed of greater than 40 mph. Traffic count data was available for five hours of the weekday between 7:00 to 9:00 AM and between 3:00 to 6:00 PM. Traffic forecasts were developed hourly for major and minor street approaches based on the forecasting methodologies described within the TIS. A summary of forecasts for available hours is shown below for the year 2024 growth and pipeline scenarios. As shown, the major east-west approach street volumes well exceed 300 entering vehicles per hour with an average hourly volume of between 570 and 630 noted between the analysis conditions. Volumes range between 140 and 280 entering vehicles on the north-south minor street approaches with an average of between 200 and 215 noted hourly. These are vehicle volumes ONLY without forecasting north-south pedestrian and bike volumes. From the TIS, the average control delay for worst hour was about 170 second during the AM peak hour based on year 2024 growth rate analyses and 75 seconds based on year 2024 pipeline analyses. For all practical purposes, it is suggested that thresholds for the all-way stop are met as control delays well exceed thresholds and average vehicle volumes alone exceed criteria. Yes vehicle volumes are not specifically satisfied for the minor approaches for afternoon hours, but these forecasts do not reflect the pedestrian and bicycle volumes that are characteristic of a very active Bozeman community; especially given many of the water and walking features expected with the Lakes at Valley West development. Thus and again, this supplemental study stresses that from a practical perspective, given delays and that all volumes thresholds are likely to be met with pedestrian and bike activity, that an all way stop TheLakesatValleyWest,SupplementalTISAnalysis#2 Page 5 is a reasonable and practical interim improvement to assure vehicle and pedestrian safety for the Laurel Parkway/Durston Road intersection. 0.4 D. The 80 percent criterion would not apply here again as collision histories are currently low for the intersection. 0.5. Beyond interim improvement and volume justifications, further support of a signal based on MUTCD guidelines would include: i “The need to control left turn conflicts.” As indicated, the southbound left-turn impact is the primary reason for LOS issues at the intersection. i “The need to control vehicle/pedestrian conflicts near locations that generate high pedestrian volumes.” Again as indicated, Bozeman is an active community and this intersection is situated within a growing residential neighborhood desiring access to the water features and trails of the Lakes of Valley West development. The nearest protected crossing would be ½ mile to the east at the Cottonwood Road/Durston Road intersection; which is a spacing sufficient enough for pedestrians to risk uncontrolled crossings as to not circumvent what would be one-mile round trip back to Laurel Parkway. Thus, this criterion can be used in justification of a controlled crossing promoted via the all-way stop. i “A intersection of two residential neighborhood collector (through) streets of similar design and operating characteristics where multi-way stop control would improve traffic operational characteristics of the intersection.” Laurel Parkway will evolve into a residential collector as the neighborhood develops. To that end, the City has been promoting the design of roundabouts at major intersections located along the roadway. Intersecting with the Durston Road arterial, a four way stop would “improve traffic operational characteristics of the intersection.” It is understood that some of the rationale in justification of the all way stop is circumstantial and less finite without current collision histories and hourly volume, pedestrian, and bike data being used for support. However, given the combination of poor traffic operations, the advent of consistently high hourly forecast traffic volumes, and given this intersection will become a focal point of pedestrian and bicycle activity, it is in the best interests of the neighborhood that this all-way stop be developed to preserve traffic operations and safety. Again, a future analysis and justification can be provided to remove the all-way stop as east-west roadway connections are promoted in the future. 3. SUMMARY Supplemental analyses #2 of the Lakes at Valley West Traffic Impact Study (TIS) confirms that a basic signal system will preserve traffic operations and safety at the Cottonwood Road/Durston Road intersection through year 2024. Turn lane and signal improvements would likely be warranted following this forecast horizon. Furthermore, this study reinforces the conclusion for the development of a four-way stop at the Laurel Parkway/Durston Road intersection in order to preserve traffic operations and pedestrian/bicycle safety as based on a review of MUTCD guidelines. It is anticipated the removal of this four way stop could occur following the construction of future east-west arterials to Cottonwood Road, as traffic volumes will likely decrease at the intersection. Thus, this should be considered a temporary or interim improvement measure for the intersection.