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BILLINGS CLINIC – BOZEMAN TRAFFIC IMPACT STUDY
15063.01
Billings Clinic
2800 10th Avenue North
Billings, MT 59101
September 20 20
Billings Clinic TIS i
TABLE OF CONTENTS
INTRODUCTION ..................................................................................................................................... 1
SITE LOCATION & DESCRIPTION ............................................................................................................. 1
SITE DEVELOPMENT PLAN ....................................................................................................................... 1
EXISTING CONDITIONS .......................................................................................................................... 4
Streets .............................................................................................................................................. 4
Intersections ...................................................................................................................................... 5
Bicycle/Pedestrian Facilities ................................................................................................................ 7
Traffic Volumes.................................................................................................................................. 7
Crash History .................................................................................................................................... 7
Intersection Capacity ....................................................................................................................... 10
TRIP GENERATION ................................................................................................................................ 10
TRIP DISTRIBUTION ............................................................................................................................... 14
TRAFFIC ASSIGNMENT .......................................................................................................................... 15
TRAFFIC IMPACTS ................................................................................................................................. 15
Traffic Volumes................................................................................................................................ 15
Intersection Capacity ....................................................................................................................... 15
Mitigation Alternatives ..................................................................................................................... 24
CONCLUSIONS & RECOMMENDATIONS .............................................................................................. 27
Conclusions .................................................................................................................................... 27
Recommendations ........................................................................................................................... 30
APPENDICES
APPENDIX A – TRAFFIC COUNT DATA
APPENDIX B – CAPACITY CALCULATIONS – EXISTING CONDITIONS (2020)
APPENDIX C – INTERNAL CAPTURE WORKSHEETS – FULL BUILDOUT (2040)
APPENDIX D – CAPACITY CALCULATIONS – PHASE 1 (2021) AND FULL BUILDOUT (2040)
APPENDIX E – AUXILIARY TURN LANE AND SIGNAL WARRANTS – FULL BUILDOUT (2040)
APPENDIX F – CAPACITY CALCULATIONS – FULL BUILDOUT (2040) – IMPROVED
LIST OF TABLES
TABLE 1: INTERSECTION CRASH FREQUENCY/SEVERITY SUMMARY ......................................................... 9
TABLE 2: INTERSECTION CRASH COLLISION TYPES ............................................................................... 10
TABLE 3: EXISTING CONDITIONS (2020) CAPACITY CALCULATION SUMMARY ...................................... 11
TABLE 4: PHASE 1 (2021) TRIP GENERATION SUMMARY ........................................................................ 12
Billings Clinic TIS ii
TABLE 5: FULL BUILDOUT (2040) TRIP GENERATION SUMMARY ............................................................. 13
TABLE 6: PHASE 1 (2021) CAPACITY CALCULATION SUMMARY ........................................................ 20-21
TABLE 7: FULL BUILDOUT (2040) CAPACITY CALCULATION SUMMARY ............................................. 22-23
TABLE 8: FULL BUILDOUT (2040) TURN WARRANT SUMMARY ................................................................ 25
TABLE 9: FULL BUILDOUT (2040) TRAFFIC SIGNAL WARRANT SUMMARY ............................................... 27
TABLE 10: FULL BUILDOUT (2040) IMPROVED CAPACITY CALCULATIONS ............................................. 28
LIST OF FIGURES
FIGURE 1: SITE LOCATION ..................................................................................................................... 2
FIGURE 2: FULL BUILD OUT (2040) SITE PLAN ......................................................................................... 3
FIGURE 3: EXISTING (2020) TRAFFIC VOLUMES ....................................................................................... 8
FIGURE 4: PHASE 1 (2021) TRIP DISTRIBUTION AND ASSIGNMENTS ...................................................... 16
FIGURE 5: FULL BUILDOUT (2040) TRIP DISTRIBUTION AND ASSIGNMENTS .......................................... 17
FIGURE 6: PHASE 1 (2021) TRAFFIC VOLUMES ...................................................................................... 18
FIGURE 7: FULL BUILDOUT (2040) TRAFFIC VOLUMES ........................................................................... 19
Billings Clinic-Bozeman TIS 1
INTRODUCTION
This traffic impact study (TIS) summarizes the projected impacts associated with a large, mixed-use development in Bozeman,
Montana. The property owner and developer for the project is Billings Clinic. The purpose of the study was to assess the
traffic-related impacts that the project may have on the surrounding transportation system and to provide recommendations to
mitigate any such impacts. The methodology and analysis procedures used in this study employ the latest technology and
nationally accepted standards in the areas of site development and transportation impact assessment. Recommendations made
in this report are based on professional judgment and these principles.
SITE LOCATION & DESCRIPTION
The Billings Clinic-Bozeman development site is generally located southwest of East Valley Center Road between North 27th
Avenue and Davis Lane. The site is bordered by Bozeman School District property to the south, Cattail Lake Subdivision
Public Park to the southwest, Interstate 90 to the northeast, and by undeveloped properties to the north, east and west. The
legal description of the property is Lot 2A of Minor Subdivision 221E in Section 26, Township 1 South, Range 5 East in
Gallatin County, Montana. Figure 1 on the following page depicts the study area, including key intersections, and the location
of the project.
SITE DEVELOPMENT PLAN
The current master plan for the Billings Clinic-Bozeman development proposes construction of approximately 695,250 square
feet (SF) of medical/hospital facilities, 100,000 SF of leasable commercial (retail/office) space, 35 loft apartment units
(situated above ground-floor commercial suites), 35 two-bedroom free-standing residential units, 59 additional apartments, a
multi-level parking garage, and a public transit station, as well as development of 9.5 acres of park/open space.
The Billings Clinic-Bozeman development project will be developed in phases. Phase 1 of the project is planned to include
approximately 125,000 SF of ancillary medical (non-hospital) facilities, such as clinics, medical offices, an ambulatory surgery
center and other such out-patient medical facilities. Phase 1 will be located at the northwest corner of the property as
illustrated in Figure 1 on the following page.
Access to the Billings Clinic-Bozeman development site is planned via full movement approaches on street connections to
Davis Lane, Valley Center Road, North 27th Avenue, and Catamount Street. As of this writing, it is expected that Phase 1
development will construct street connections on East Valley Center Road (approximately 800 feet northwest of the North
27th Avenue intersection) and on North 27th Avenue (approximately 400 feet south of East Valley Center Road).
On-site parking for the Billings Clinic-Bozeman development site will be accommodated via a multi-level parking garage as
well as shared and dedicated parking lots and limited on-street parking. Phase 1 parking will be provided via surface parking
lots and on-street parking. As of this time, a detailed parking configuration has not been established for Phase 1 development.
Buildout and occupancy of Phase 1 of the Billings Clinic-Bozeman site is projected for late 2021. Figure 2 on page 3 shows
the size and location of the full buildout, including new access roadways. Completion of development for the full site is
expected by approximately 2040.
Billings Clinic-Bozeman TIS 2
Fig ure 1: Site Location
Billings Clinic-Bozeman TIS 3
Figure 2: Full Buildout (2040) Site Plan
Billings Clinic-Bozeman TIS 4
EXISTING CONDITIONS
Streets
The proposed development of this project site will have a direct impact on the adjacent streets and intersections. The
following paragraphs describe the existing area roadways that are most likely to be affected by the traffic volumes generated by
this development.
Catamount Street
Catamount Street is classified as a local street by the Montana Department of Transportation (MDT) functional classification
system and as a minor arterial in the Bozeman Transportation Master Plan . Between Davis Lane and North 27th Avenue,
Catamount Street has a two-lane typical section with bike lanes, curb and gutter, and sidewalk on both sides. The posted
speed limit on Catamount Street is 25 mph.
Catron Street
Catron Street is classified as a local street by both MDT and the City of Bozeman. Between Davis Lane and North 27th
Avenue, Catron Street has a paved surface width of approximately 30 feet with no pavement markings except at crosswalks.
Catron Street has curb and gutter and sidewalk on both sides. The speed limit on Catron Street is posted at 25 mph.
Cattail Street
Cattail Street is classified as a local street by MDT and as a collector by the City of Bozeman. Between Davis Lane and North
27th Avenue, Cattail Street has a paved surface width of approximately 35 feet with no pavement markings except at
crosswalks, and curb and gutter and sidewalk along both sides. Between North 27th Avenue and North 19th Avenue, Cattail
street has a paved surface width of approximately 45 feet with no curb and gutter or pavement markings to delineate lanes or
shoulders. In this stretch, there is sidewalk along the north side. The posted speed limit on Cattail Street is 25 mph.
Davis Lane
Davis Lane is classified as a local street by MDT and as a minor arterial by the City of Bozeman. Davis Lane has a two-lane
typical section with gravel shoulders from East Valley Center Road to approximately ¼ mile north of Catamount Street where
it then has curb and gutter on both sides and sidewalk on the east side. The posted speed limit on Davis Lane is 35 mph.
East Valley Center Road
East Valley Center Road is classified as a minor arterial by MDT and as a principal arterial by the City of Bozeman. West of
North 27th Avenue, East Valley Center Road has a two-lane typical section with paved shoulders and the posted speed limit is
60 mph. East of North 27th Avenue, the street is median-separated with two lanes eastbound and one lane westbound, and
with a left-turn lane onto North 27th Avenue. The street has paved shoulders and the posted speed limit in this section is 45
mph.
Westlake Road
Westlake Road is a County facility that is classified as a local street by both MDT and the City of Bozeman. Between Davis
Lane and East Valley Center Road, Westlake Road has a gravel surface width of approximately 25 feet with no pavement
markings. There is no posted speed limit on Westlake Road.
Billings Clinic-Bozeman TIS 5
North 19th Avenue
North 19th Avenue is classified as a principal arterial by both MDT and the City of Bozeman. Adjacent to the project site,
North 19th Avenue has a four-lane, median-separated typical section with dedicated turn lanes at the intersections with Valley
Center Road, Cattail Street, and two private approaches. There is an eight-foot wide multi-use path along the west side of the
street between Cattail Street and Valley Center Road and on the east side along the frontage of the Ford dealership. The street
has paved shoulders and a posted speed limit of 40 mph.
North 27th Avenue
North 27th Avenue is classified as a local street by MDT and as a collector by the City of Bozeman. North 27th Avenue has a
two-lane typical section with paved shoulders starting at East Valley Center Road and extending south approximately 900 feet
to the north property boundary for the Bozeman School District #7 property. The School District property has access onto
North 27th Avenue and will continue to have access throughout construction. It is anticipated that the land will be sold and
developed by the full phase scenario (2040). South of the school district property the typical section includes bike lanes in
both directions, on-street, parallel parking on the west side, and both curb and gutter, and sidewalk on both sides. The
sidewalk ends at Catron Street and begins again on the west side only at Cattail Street. The posted speed limit is 25 mph.
Intersections
The following paragraphs describe the existing major street intersections that are adjacent to the development site and will
potentially be impacted by the new development.
Davis Lane / East Valley Center Road
The intersection of Davis Lane and East Valley Center Road is a three-legged intersection that is stop-controlled on the south
approach (Davis Lane). All legs have single entering and exiting lanes (no auxiliary turn bays).
Davis Lane / Westlake Road
The intersection of Davis Lane and Westlake Road is a four-legged intersection that is stop-controlled on the east approach
(Westlake Road) only. There is currently no control on the west approach, which is an unpaved private driveway. All legs have
single entering and exiting lanes (no auxiliary turn bays). The west (private drive) approach is offset approximately 20 feet to
the north (centerline to centerline) from the east (Westlake Road) approach.
East Valley Center Road / Westlake Road
The intersection of East Valley Center Road and Westlake Road is a three-legged intersection that is stop-controlled on the
south approach (Westlake Road). All legs have single entering and exiting lanes (no auxiliary turn bays).
East Valley Center Road / North 27th Avenue
The intersection of East Valley Center Road and North 27th Avenue is a three-legged intersection that is stop-controlled on
the south approach (North 27th Avenue). The south approach has dedicated left- and right-turn lanes, the east approach has
dedicated thru and left-turn lanes, and the west approach has a single, shared-movement lane. All three intersection legs have
single outbound lanes.
Catamount Street / Davis Lane
The intersection of Catamount Street and Davis Lane is a four-legged intersection that is stop-controlled on the east approach
(Catamount Street). There is currently no control on the west leg, which is an unpaved private road (farm field access). All legs
Billings Clinic-Bozeman TIS 6
have single entering and exiting lanes (no auxiliary turn bays) and the entering lane on each leg allows for all turning
movements. The west (private road) approach is offset approximately 12 feet to the south (centerline to centerline) from the
east (Catamount Street) approach.
Catamount Street / North 27th Avenue
The intersection of Catamount Street and North 27th Avenue is a four-legged intersection that is stop-controlled on the east
and west approaches (Catamount Street). All legs have single entering and exiting lanes (no auxiliary turn bays).
Catamount Street / East Valley Center Road
The intersection of Catamount Street and East Valley Center Road is a four-legged intersection that is stop-controlled on the
east and west approaches (Catamount Street). The north and south approaches each have two dedicated thru lanes and one
median-separated, dedicated left-turn lane. The east and west legs each have a single entering lane with unrestricted turning
movements. Note that the east leg serves as a private access approach for a hotel and a restaurant.
Catron Street / North 27th Avenue
The intersection of Catron Street and North 27th Avenue is a four-legged intersection that is stop-controlled on the east and
west approaches (Catron Street). All legs have single entering and exiting lanes (no auxiliary turn bays).
Cattail Street / Davis Lane
The intersection of Cattail Street and Davis Lane is a four-legged intersection that is stop-controlled on the east and west
approaches (Cattail Street). All legs have single entering and exiting lanes (no auxiliary turn bays).
Cattail Street / North 27th Avenue
The intersection of Cattail Street and North 27th Avenue is a three-legged intersection that is stop-controlled on the west leg
(Cattail Street). All legs have single entering and exiting lanes (no auxiliary turn bays)
Cattail Street / North 19th Avenue
The intersection of Cattail Street and North 19th Avenue is a four-legged intersection that is controlled with a traffic signal.
Each approach has a dedicated left-turn lane. The east and west approaches (Cattail Street) both have shared thru/right-turn
lanes. The north approach (North 19th Avenue) has two dedicated thru lanes and a dedicated right-turn lane. The south
approach has a dedicated thru lane and a shared thru/right-turn lane. The traffic signal operates with eight phases and is fully
actuated. All four approaches are served by protected left-turn phases, and the southbound approach has a right-turn overlap.
East Valley Center Road / North 19th Avenue
The intersection of East Valley Center Road and North 19th Avenue is a four-legged intersection that is controlled with a
traffic signal. The west approach (Valley Center Road) has a shared thru/left and a dedicated right-turn lane. The east
approach has a dedicated left-turn lane and a shared thru/right lane. The north approach (North 19th Avenue) has two
dedicated thru lanes and a both dedicated right-turn lane and left-turn lane. The south approach has dual, dedicated left-turn
lanes, a dedicated thru lane and a shared thru/right-turn lane. The traffic signal is coordinated with the North 19 th Avenue
signals. The south approach is served by a protected left-turn phase, and the west approach has a right-turn overlap.
Billings Clinic-Bozeman TIS 7
Bicycle/Pedestrian Facilities
There are existing bike lanes on North 27th Avenue from Cattail Street north to the boundary between the School District #7
and Billings Clinic-Bozeman properties, as well as along Catamount Street between Davis Lane and North 27th Avenue.
There is also a shared use path along the west side of North 27th Avenue between Cattail Street and Catamount Street.
The Billings Clinic Master Plan includes sidewalks on both sides of the street following City standards. It also includes
sidewalks on both sides of private access drives where feasible to provide a connected pedestrian system. The Billings Clinic
Master Plan also plans for campus trails (6 and 10 feet wide) that access each of the buildings within the Billings Clinic campus
and external roadways. Additionally, the campus trails will connect to a trail system within Cattail Creek Subdivision that
extends throughout the general area connecting with other bike and pedestrian facilities. The Visionary Active Transportation
Network anticipates that there will be bike lanes or shared use paths along East Valley Center Road, Davis Lane and
Catamount Street which should directly link the Billings Clinic campus to these exterior network streets and active
transportation paths. All subdivisions in the area also have developed sidewalks. It is recommended in the Bozeman
Transportation Master Plan (TMP) that the northern portion of North 27th Avenue have bicycle lanes which would allow
complete connectivity of the Billings Clinic to the future active transportation network.
Traffic Volumes
Weekday AM and PM peak hour turning movement counts were collected for the above-listed study area intersections on
Thursday, June 14 and Thursday, June 21, 2018. Counts for two internal intersections (East Valley Center Road/North 27th
Avenue PM peak and East Valley Center Road/Westlake Road) were estimated based on data from adjacent study area
intersections. In general, the weekday peak hour periods were found to occur from 7:30 to 8:30 AM and 5:00 to 6:00 PM.
Raw count data was adjusted for seasonal variation using Montana Department of Transportation (MDT) seasonal adjustment
factors.
Due to inability to gather accurate traffic counts in 2020 as a result of Covid-19, existing conditions (2020 volumes) were
calculated from 2018 counts with an annual growth rate of 4-percent for all movements. New traffic volume growth, as
anticipated in the traffic impact studies from the nearby developments of Winco, Catron Crossing, Creekside Phase 1 and 2,
and The Springs Living (currently at 40% occupancy), as well as others were included in the growth calculation. Figure 3 on
the following page summarizes the resulting calculated Existing Conditions (2020) peak hour turning movement volumes for
the AM and PM peak hours. Detailed traffic count data worksheets are included in Appendix A.
Crash History
Historical crash data was obtained from MDT for the 5-year period from January 1, 2013 through December 31, 2017. The
data was analyzed for the purposes of calculating intersection crash and severity rates and evaluating collision type trends.
Note that data was only available for five (5) study area intersections. Table 1 illustrates the results of the historical crash
analysis. Intersection crash rates were calculated on the standard basis of crashes per million vehicles entering (MVE) for each
intersection. The MVE metric was estimated based on 2018 peak hour traffic counts and published historical ADT volumes
from the MDT website. Crash rates for the study area intersections ranged from 0.08 crashes/MVE to 0.46 crashes/MVE.
As a means of evaluating the historical crash frequency rates, Sanderson Stewart calculated expected rates using the predictive
crash rate formulas in the American Association of State Highway Transportation Officials (AASHTO) Highway Safety
Manual (HSM). The process involves calculating the number of crashes predicted in a year based on traffic demand (AADTs)
and various physical and traffic environment-based conditions, such as lane configurations, traffic signal phasing, and
Billings Clinic-Bozeman TIS 8
Figure 3: Existing Conditions (2020) Traffic Volumes
Billings Clinic-Bozeman TIS 9
approach speeds. The calculation results in a crashes-per-year prediction. Sanderson Stewart then back-calculated a frequency
rate on the basis of million vehicles entering for the sake of comparison with the actual historical crash rate. The results of the
calculations for this study showed that the crash frequency prediction for the intersection of Catron Street and North 27th
Avenue was approximately 50% higher than the calculated historical rate, while the prediction for the intersection of Davis
Lane and Cattail Street was six times higher than the historical rate. For the remaining study area intersections that were
analyzed, the predicted HSM rates were very similar to the historical rates. The HSM rate predictions and 5-year crash totals
for each intersection are summarized in Table 1.
Severity index is defined as the weighted average by crash severity, including fatality, injury, and property damage only (PDO)
crashes. Severity rate is defined as the crash rate multiplied by the severity index. Severity rates for study area intersections
were in this case found to be relatively low with one exception. There was one fatal crash reported at the intersection of
Catamount Street and North 27th Avenue, resulting in a severity rate of 2.07 that is more than four times the crash frequency
rate. There were six injury crashes reported at three other intersections. Severity rate calculation results are also summarized in
Table 1 above.
Sanderson Stewart also performed an analysis of collision classification to determine if any patterns could be identified. Table
2 (page 10) illustrates the results of that analysis, which showed that 73% of the reported crashes at the intersection of North
19th Avenue and Cattail Street were classified as rear-end collisions. This is a common crash type at signalized intersections
because the signalized control is dynamic, thereby requiring that drivers recognize and react to changing conditions in real
time. However, there are some specific and potentially correctable conditions that can cause an increase in rear-end collisions.
Looking more closely at the individual crash reports for the intersection, 9 of the 11 rear end crashes occurred either
northbound (8) or southbound (1) on North 19th Avenue where the speed limit is posted at 40 mph and 85th percentile speeds
are likely higher yet. Therefore, it is possible that the higher speeds in the corridor are contributing to the high percentage of
rear-end collisions. It is also worth noting that 4 of the 11 rear end crashes occurred under what was classified as icy or wet
roadway conditions.
Another potential contributing factor for rear end collisions at a signalized intersection is a yellow change interval that is too
short for the prevailing operating speeds in that corridor. Based on the application of yellow change interval formulas from the
Institute of Transportation Engineers (ITE) Traffic Engineering Handbook with assumed 45 mph thru-movement operating
speeds and assumed 35 mph turning movement operating speeds, it was calculated that the “design” yellow change intervals
should be 4.4 seconds for thru traffic, 3.7 seconds for turning traffic in the northbound direction, 4.2 seconds for through
traffic, and 3.5 seconds for turning traffic in the southbound direction. The existing signal timing plan uses a change interval of
3.9 seconds for thru traffic and 3.0 seconds for left-turning traffic for both the northbound and southbound phases. The
Table 1: Intersection Crash Frequency/Severity
PDO Injury Fatality Frequency Severity Annual
Crashes
Frequency
(crashes/MVE)
Davis Lane & East Valley Center Road 7756 5 4 1 0 0.35 0.49 1.1 0.39
Catamount Street & North 27th Avenue 2406 2 1 0 1 0.46 2.07 0.4 0.46
Catron Street & North 27th Avenue 4217 2 1 1 0 0.26 0.52 0.6 0.39
Davis Lane & Cattail Street 6816 1 1 0 0 0.08 0.08 1.2 0.48
Cattail Street & North 19th Avenue 28841 15 11 4 0 0.28 0.43 3.2 0.30
2 Crashes reported from January 1, 2013 to December 31, 2017
3 Crash and severity rates expressed as crashes per million vehicles entering (MVE) based on MDT severity factors
⁴Rates calculated using Highway Safety Manual (HSM) 1st Edition predictive methodology
1 Daily Entering Volume (DEV) estimated from 2013 through 2017 MDT published ADTs.
Intersection
Crash Rates (per MVE 3)Crash Type 2013-2017
DEV 1
Reported
Crashes 2
HSM Predictions ⁴
Billings Clinic-Bozeman TIS 10
variance between actual and recommended design change interval may or may not be significant relative to the high
percentage of rear-end crashes at this location.
Other factors that typically contribute to a high occurrence of rear end crashes include poor signal visibility, a lack of dedicated
turn lanes where high turning movement demands are prevalent, and poor signal coordination in a corridor. However, none
of those factors seem to be an obvious issue for the North 19th Avenue/Cattail Street intersection.
None of the other study area intersections for which crash data was available exhibited any significant collision type trends.
As such, no further investigations related to collision type were pursued.
Intersection Capacity
Existing Conditions (2020) capacity calculations were performed for the signalized study area intersection using Synchro,
Version 10, which relies on 2010 Highway Capacity Manual (HCM2010) (Transportation Research Board, 2010)
methodologies and for the stop-controlled intersections using Highway Capacity Software (HCS7). The HCM defines level of
service (LOS) as “a quality measure describing operational conditions within a traffic stream, generally in terms of such service
measures as speed and travel time, freedom to maneuver, traffic interruptions, comfort, and convenience.” LOS is a qualitative
measure of the performance of an intersection with values ranging from LOS A, indicating good operation and low vehicle
delays, to LOS F, which indicates congestion and longer vehicle delays. LOS C is generally considered as the minimum
acceptable performance level for planning and design purposes in Bozeman.
The results of the Existing Conditions (2020) intersection capacity calculations showed that all the study area unsignalized
intersections operate at LOS C or better during the AM and PM peak hours. Projected 95th percentile queuing is minimal
except at the two signalized intersections. Cattail Street/North 19th Avenue has queues on the east and westbound
approaches during AM and PM peak hours. North 19th Avenue/East Valley Center Road has 95th percentile queuing on
three of the approaches in the PM peak hour and one in the AM peak hour. North 19th Avenue/East Valley Center Road is
at LOS D in the PM peak hour. Table 3 on the following page displays the results of the Existing Conditions (2020) capacity
calculations. Capacity calculation worksheets for each of the study area intersections can be found in Appendix B.
TRIP GENERATION
An accurate estimate of site-generated traffic must be made to analyze the impacts of a new development. This study utilized
Trip Generation, 10th Edition, published by the Institute of Transportation Engineers (ITE), which is the most widely
accepted source for determining trip generation projections. For the purposes of this study, trip generation was calculated
Rear End Right Angle Sideswipe Lost Control Left Turn OD Head On Fixed Object Roll Over Total
Davis Lane & East Valley Center Road 1 2 0 0 0 0 1 1 5
Catamount Street & North 27th Avenue 0 1 0 0 0 0 1 0 2
Catron Street & North 27th Avenue 0 2 0 0 0 0 0 0 2
Davis Lane & Cattail Street 0 0 1 0 0 0 0 0 1
Cattail Street & North 19th Avenue 11 1 0 1 1 1 0 0 15
Intersection
Collision Type
Table 2: Intersection Crash Collision Types
Billings Clinic-Bozeman TIS 11
Table 3: Existing Conditions (2020) Capacity Calculations
Avg
Delay
(s/veh) LOS
95th %
Queue
(veh)
Avg
Delay
(s/veh) LOS
95th %
Queue
(veh)
EB 0.0 A 0 0.0 A 0
WB 0.6 A 0 0.1 A 0
NB 13.8 B 1 21.3 C 3
EB 8.8 A 0 9.0 A 0
WB 10.1 B 0 10.6 B 0
NB 0.0 A 0 0.1 A 0
SB 0.1 A 0 0.0 A 0
EB 0.0 A 0 0.0 A 0
WB 0.0 A 0 0.0 A 0
NB 10.1 B 0 12.8 B 1
EB 0.0 A 0 0.0 A 0
WB 0.4 A 0 0.3 A 0
NB 10.6 B 1 12.9 B 1
WB 10.2 B 1 10.5 B 1
NB 0.0 A 0 0.0 A 0
SB 0.3 A 0 0.5 A 0
EB 9.6 A 1 10.0 A 1
WB 9.6 A 1 11.1 B 1
NB 1.8 A 0 1.0 A 0
SB 0.0 A 0 0.2 A 0
EB 9.9 A 1 10.3 B 1
WB 12.2 B 1 15.1 C 1
NB 2.7 A 1 1.8 A 1
SB 0.0 A 0 0.4 A 0
EB 10.5 B 1 11.9 B 1
WB 10.2 B 1 13.3 B 2
NB 1.4 A 0 1.8 A 0
SB 2.2 A 0 3.8 A 1
EB 12.8 B 1 22.5 C 2
WB 12.1 B 1 20.5 C 2
NB 0.0 A 0 0.1 A 0
SB 0.2 A 0 0.1 A 0
EB 9.4 A 1 9.8 A 1
NB 2.4 A 1 4.1 A 1
SB 0.0 A 0 0.0 A 0
EB 29.5 C 2 51.6 D 5
WB 42.1 D 1 78.4 E 4
NB 9.3 A 9 14.5 B 17
SB 10.1 B 13 16.3 B 17
Intersection 12.7 B -- 22.4 C --
EB 43.7 D 18 41.6 D 19
WB 33.4 C 1 39.8 D 2
NB 30.1 C 8 52.5 D 13
SB 18.2 B 12 23.3 C 10
Intersection 28.7 C -- 38.4 D --
Intersection Control One-Way Stop Controlled (NB)
Intersection Approach
Existing (2020)
AM Peak PM Peak
Davis Lane &
E Valley Center Road
Intersection Control Two-Way Stop Controlled (EB/WB)
Davis Lane &
Westlake Road
Intersection Control One-Way Stop Controlled (NB)
Westlake Road &
E Valley Center Road
Intersection Control One-Way Stop Controlled (NB)
North 27th Avenue &
E Valley Center Road
Intersection Control One-Way Stop Controlled (WB)
Catamount Street &
E Valley Center Road
Intersection Control Two-Way Stop Controlled (EB/WB)
Catron Street &
North 27th Avenue
Davis Lane &
Catamount Street
Intersection Control Two-Way Stop Controlled (EB/WB)
Catamount Street &
North 27th Avenue
Intersection Control Two-Way Stop Controlled (EB/WB)
Intersection Control Two-Way Stop Controlled (EB/WB)
Davis Lane &
Cattail Street
Intersection Control One-Way Stop Controlled (EB)
Intersection Control Signalized
North 19th Avenue &
E Valley Center Rd
Cattail Street &
North 27th Avenue
Intersection Control Signalized
Cattail Street &
North 19th Avenue
Billings Clinic-Bozeman TIS 12
using several land use categories. Tables 4 and 5 (pages 12 and 13) illustrate the results of the trip generation calculations for
the Phase 1 (2021) scenario and for the Full Buildout (2040) scenario, respectively.
At full buildout and occupancy, the Billings Clinic-Bozeman mixed-use development is projected to generate a total of 18,889
gross average weekday trips with 1550 trips (1104 entering/446 exiting) generated during the AM peak hour and 1714 trips
(618 entering/1096 exiting) generated during the PM peak hour. For Phase 1, the anticipated development is projected to
generate 4448 gross average weekday trips with 374 trips (291 entering/83 exiting) generated during the AM peak hour and
427 trips (121 entering/306 exiting) generated during the PM peak hour.
Trip generation projections provide an estimate of the total number of trips that would be generated by a proposed
development. However, in order to estimate the net number of new trips made by personal vehicles external to the site,
adjustments must often be made to account for internal capture trips, pass-by trips, and trips made by alternate modes.
Internal capture (IC) trips are those trips that do not have origins or destinations external to a project site. Since IC trips
occur internally, they do not have an impact on external traffic operations. IC trips most often occur in mixed-use
developments where residential, commercial, and office-related land uses exhibit a high rate of internal trip exchange. Since
Phase 1 development for this site is expected to include only targeted medical/medical office facilities, internal capture would
likely be minimal. However, the Full Buildout (2040) land development plan is likely to generate a significant number of
internal capture trips due to the mixed-used nature of the project. Using standard ITE procedures, the development is
projected to generate 984 weekday IC trips (492 entering/492 exiting) with 144 IC trips (72 entering/72 exiting) during the
AM peak hour and 210 IC trips (105 entering/105 exiting) during the PM peak hour. The IC trip calculation results for each
individual and applicable land use are summarized in Table 5 (page 13). Internal capture calculation worksheets for this study
are included in Appendix C.
Pass-by trips are those trips that are made as intermediate stops on the way from a point of origin to a primary trip destination.
Pass-by trips are attracted from traffic “passing by” on an adjacent street that offers direct access to that site. Pass-by trips are
primarily attracted by commercial type land uses such as restaurants, convenience markets and gas stations. Once again, due to
the nature of planned development, Phase 1 is not expected to generate a substantial volume of pass-by trips. Therefore, pass-
by trips were considered as negligible for the Phase 1 analysis. However, since the project is ultimately planned to include a
Table 4: Trip Generation Su mmary – Phase 1 (2021)
Intensity Units total enter exit total enter exit total enter exit
Ambulatory Surgery Building 1 29.25 1000 ft 2 GFA 1116 558 558 108 84 24 96 28 68
Clinic/Medical Office Building 2 95.75 1000 ft 2 GFA 3332 1666 1666 266 207 59 331 93 238
Total Gross Trips 4448 2224 2224 374 291 83 427 121 306
(1) Ambulatory Surgery Building - Land Use 630* Units = 1000 ft 2 Gross Floor Area (GFA)
Average Weekday: Average Rate = 38.16 (50% entering/50% exiting)
Peak Hour of the Adjacent Street, One Hour between 7 and 9 AM: Average Rate = 3.69 (78% entering/22% exiting)
Peak Hour of the Adjacent Street, One Hour between 4 and 6 PM: Average Rate = 3.28 (29% entering/71% exiting)
(2) Clinic/Medica Office Building - Land Use 720* Units = 1000 ft 2 Gross Floor Area (GFA)
Average Weekday: Average Rate = 34.80 (50% entering/50% exiting)
Peak Hour of the Adjacent Street, One Hour between 7 and 9 AM: Average Rate = 2.78 (78% entering/22% exiting)
Peak Hour of the Adjacent Street, One Hour between 4 and 6 PM: Average Rate = 3.46 (28% entering/72% exiting)
*Trip Generation, 10th Edition , Institute of Transportation Engineers, 2017
** Trip Generation Handbook, 3rd Edition , Institute of Transportation Engineers, 2017
Phase 1 Core Medical Campus
Land Use Independent Variable Average Weekday AM Peak Hour PM Peak Hour
Billings Clinic-Bozeman TIS 13
Intensity Units total enter exit total enter exit total enter exit
Clinical/Med Office Bldg¹ 124.75 1000 ft 2 GFA 4760 2380 2380 460 359 101 409 119 290
Internal Capture Trips** 29 10 19 10 5 5 3 1 2
Ambulatory Surgery Bldg² 40.5 1000 ft 2 GFA 1409 705 704 113 88 25 140 39 101
Internal Capture Trips** 9 3 6 4 2 2 1 0 1
Clinic Building/Office Bldg 2¹ 80 1000 ft 2 GFA 3053 1527 1526 295 230 65 262 76 186
Internal Capture Trips** 18 6 12 6 3 3 2 1 1
Hospital³ 450 1000 ft 2 GFA 4824 2412 2412 401 273 128 437 140 297
Internal Capture Trips** 101 34 67 36 17 19 11 3 8
General Office Building ⁴25 1000 ft 2 GFA 244 122 122 29 25 4 29 5 24
Internal Capture Trips** 6 2 4 2 1 1 1 0 1
Shopping Center ⁵60 1000 ft 2 GFA 2265 1133 1132 56 35 21 229 110 119
Internal Capture Trips** 362 185 177 23 14 9 87 42 45
Pass-By Trips** (Avg. Rate = 34%) 647 322 325 11 7 4 48 23 25
High-Turnover (Sit-Down) Restaurant ⁶15 1000 ft 2 GFA 1683 842 841 149 82 67 147 91 56
Internal Capture Trips** 361 229 132 54 29 25 64 33 31
Pass-By Trips** (Avg. Rate = 43%) 569 264 305 41 23 18 36 25 11
Single-Family Detached Housing ⁷35 Dwelling Units 330 165 165 26 7 19 35 22 13
Internal Capture Trips** 37 9 28 3 0 3 15 9 6
Multifamily Housing (Mid-Rise) ⁸59 Dwelling Units 321 161 160 21 5 16 26 16 10
Internal Capture Trips** 61 14 47 6 1 5 26 16 10
18889 9447 9442 1550 1104 446 1714 618 1096
984 492 492 144 72 72 210 105 105
1216 586 630 52 30 22 84 48 36
16689 8369 8320 1354 1002 352 1420 465 955
(1) Clinic/Med Office Bldg - Land Use 630* Units = 1000 ft 2 Gross Floor Area (GFA)
Average Weekday: Average Rate = 38.16 (50% entering/50% exiting)
Peak Hour of the Adjacent Street, One Hour between 7 and 9 AM: Average Rate = 3.69 (78% entering/22% exiting)
Peak Hour of the Adjacent Street, One Hour between 4 and 6 PM: Average Rate = 3.28 (29% entering/71% exiting)
(2) Ambulatory/Surgery Building - Land Use 720* Units = 1000 ft 2 Gross Floor Area (GFA)
Average Weekday: Average Rate = 34.8 (50% entering/50% exiting)
Peak Hour of the Adjacent Street, One Hour between 7 and 9 AM: Average Rate = 2.78 (78% entering/22% exiting)
Peak Hour of the Adjacent Street, One Hour between 4 and 6 PM: Average Rate = 3.46 (28% entering/72% exiting)
(3) Hospital - Land Use 610* Units = 1000 ft 2 Gross Floor Area (GFA)
Average Weekday: Average Rate = 10.72 (50% entering/50% exiting)
Peak Hour of the Adjacent Street, One Hour between 7 and 9 AM: Average Rate = 0.89 (68% entering/32% exiting)
Peak Hour of the Adjacent Street, One Hour between 4 and 6 PM: Average Rate = 0.97 (32% entering/68% exiting)
(4) General Office Building - Land Use 710* Units = 1000 ft 2 Gross Floor Area (GFA)
Average Weekday: Average Rate = 9.74 (50% entering/50% exiting)
Peak Hour of the Adjacent Street, One Hour between 7 and 9 AM: Average Rate = 1.16 (86% entering/14% exiting)
Peak Hour of the Adjacent Street, One Hour between 4 and 6 PM: Average Rate = 1.15 (16% entering/84% exiting)
(5) Shopping Center - Land Use 820* Units = 1000 ft 2 Gross Floor Area (GFA)
Average Weekday: Average Rate = 37.75 (50% entering/50% exiting)
Peak Hour of the Adjacent Street, One Hour between 7 and 9 AM: Average Rate = 0.94 (62% entering/38% exiting)
Peak Hour of the Adjacent Street, One Hour between 4 and 6 PM: Average Rate = 3.81 (48% entering/52% exiting)
(6) High-Turnover (Sit-Down) Restaurant - Land Use 932* Units = 1000 ft 2 Gross Floor Area (GFA)
Average Weekday: Average Rate = 112.18 (50% entering/50% exiting)
Peak Hour of the Adjacent Street, One Hour between 7 and 9 AM: Average Rate = 9.94 (55% entering/45% exiting)
Peak Hour of the Adjacent Street, One Hour between 4 and 6 PM: Average Rate = 9.77 (62% entering/38% exiting)
(7) Single-Family Detached Housing - Land Use 210* Units = Dwelling Units
Average Weekday: Average Rate = 9.44 (50% entering/50% exiting)
Peak Hour of the Adjacent Street, One Hour between 7 and 9 AM: Average Rate = 0.74 (25% entering/75% exiting)
Peak Hour of the Adjacent Street, One Hour between 4 and 6 PM: Average Rate = 0.99 (63% entering/37% exiting)
(8) Multifamily Housing (Mid-Rise) - Land Use 221* Units = Dwelling Units
Average Weekday: Average Rate = 5.44 (50% entering/50% exiting)
Peak Hour of the Adjacent Street, One Hour between 7 and 9 AM: Average Rate = 0.36 (26% entering/74% exiting)
Peak Hour of the Adjacent Street, One Hour between 4 and 6 PM: Average Rate = 0.44 (61% entering/39% exiting)
*Trip Generation, 10th Edition , Institute of Transportation Engineers, 2017
** Trip Generation Handbook, 3rd Edition , Institute of Transportation Engineers, 2017
Land Use
Independent Variable Average Weekday AM Peak Hour PM Peak Hour
Core Medical Campus
Total Gross Trips
Total Internal Capture Trips
Total Pass-By Trips
Total New External Personal Vehicle
Auxiliary Site Development
Table 5: Trip Generation Summary – Full Buildout (2040)
Billings Clinic-Bozeman TIS 14
substantial amount of retail and restaurant development, pass-by trips are expected for the Full Buildout (2040) scenario.
Based on standard ITE procedures, it was projected that 1216 pass-by trips (586 entering/630 exiting) will be generated on a
typical weekday, including 52 pass-by trips (30 entering/22 exiting) during the AM peak hour and 84 pass-by trips (48
entering/36 exiting) during the PM peak hour. Table 5 (page 13) summarizes the pass-by trip calculations results.
A portion of the external trips generated by the Billings Clinic-Bozeman mixed-use development could be made by alternate
modes (walking, biking, transit), thereby reducing vehicular trips generated. Residents of adjacent residential neighborhoods
or people staying at nearby, off-site hotels could potentially walk or bike to the project site. The Billings Clinic Master Plan
includes sidewalks on all roads, private drives where feasible and an extensive trail system throughout the campus that will
include connections to the Cattail Lake Subdivision. The Visionary Active Transportation Network anticipates that there will
be either bike lanes or shared use paths along East Valley Road, Davis Lane and Catamount Street which should directly link
the Billings Clinic campus to these exterior network streets and active transportation paths. Since a majority of the trips to this
development are generated by medical land uses, those trips may be less likely to be made via alternate mode options. In
terms of transit potential, the closest Streamline Bus stop is at the intersection of Catron Street and North 27th Avenue, which
is over ½ mile from the site. Given the above considerations, alternate mode trips were conservatively assumed to be
negligible for the purposes of this study.
With adjustments made for internal capture and pass-by trips, at full buildout, the Billings Clinic-Bozeman mixed-use
development is projected to generate 16,689 net new external vehicular trips on a typical weekday with 1354 trips (1002
entering/352 exiting) during the AM peak hour and 1420 trips (465 entering/955 exiting) during the PM peak hour.
TRIP DISTRIBUTION
A trip distribution is an estimate of site-generated trip routing, which can be determined by several methods such as
computerized travel demand models, calculation of travel time for various available routes and/or simple inspection of
existing traffic patterns within the project area. For this study, Sanderson Stewart calculated the trip distribution scheme using
projected (2040) traffic volumes for the study area streets from the City of Bozeman Transportation Master Plan (TMP) and
the “Streets of Bozeman” Story Map. Volumes were evaluated and used to calculate separate distributions for the
residential/commercial portion and the hospital portion of the development based on reasonable expected routes for the land
uses. The percentage of trips expected for each land use group were used to weigh the two distributions and calculate a
composite distribution for the Full Buildout (2040) scenario. It included equal distribution among the southbound roadways of
Davis Lane, North 27th Street and North 19th Street. These assumptions are based upon expansions and new connections
that are anticipated in the TMP such as:
· The expansion of Cattail Avenue to a three-lane urban collector roadway with connection between North 19th
Avenue and North 27th Avenue; expansion of North 27th Avenue from Baxter Lane to Valley Center Road;
expansion of Catamount Street from North 27th Avenue to Valley Center Road to a two-lane urban minor arterial
standard.
· The reconstruction of Valley Center Road from the intersection with Valley Center Spur Road (at the underpass) to
the intersection with North 27th Avenue, to a three-lane urban principal arterial standard.
· Future road connections in the TMP including expansions of Catamount Street, Baxter Road, and Cattail Street to
the west
Billings Clinic-Bozeman TIS 15
· Transportation System Management (TSM) Improvements at the intersections of Davis Lane/Cattail Street, Davis
Lane/Catamount Street, Davis Lane/Valley Center Road and North 27th Avenue/Valley Center Road.
For Phase 1 analysis, the same distribution was used but volumes from roadway connections that are not expected to be
completed by 2021 were routed through the existing network. For the Full Buildout assumptions were made that southbound
traffic would be equally distributed between the three anticipated southbound roadways (Davis Lane, North 27th Avenue,
North 19th Avenue). Figures 4 and 5 (pages 16 and 17) present the calculated trip distribution schemes for Phase 1 (2021)
and Full Buildout (2040), respectively.
TRAFFIC ASSIGNMENT
Traffic assignment is the procedure whereby site-generated vehicle trips are assigned to study area streets, intersections, and
site access driveways based on the calculated trip distribution and the physical attributes of the development site. Using this
approach, the primary site-generated trips for the Billings Clinic-Bozeman mixed-use development were assigned to the study
area roadway network. Pass-by trips were assigned using a distribution calculated from the existing conditions counts since
pass-by trips are inherently part of the existing traffic demand pattern. The results of the traffic assignment exercise for the
AM and PM peak hours are also illustrated in Figures 4 and 5 for Phase 1 (2021) and Full Buildout (2040) scenarios,
respectively.
TRAFFIC IMPACTS
Traffic Volumes
For the purposes of this study, based on information from the Client, it was assumed that Phase 1 buildout and occupancy for
Billings Clinic mixed-use site development would occur by the end of calendar year 2021, and that full buildout and occupancy
of the entire development would occur by 2040. In addition to the site-generated traffic from the subject development,
background traffic volumes are also expected to increase for study area streets and intersections due to general growth in the
Bozeman area. New developments since 2018, including a new residential living facility (The Springs Living) that is currently
at 40 percent occupancy and an anticipated light manufacture of small goods (Catron Crossing) have contributed to a slight
growth of traffic volumes in the surrounding area. To account for the growth, Sanderson Stewart reviewed projected volume
conditions from the Bozeman TMP, the “Streets of Bozeman” Story Map, and data provided by MDT. It was determined that
an annual background growth rate of 4.0 percent for Phase 1 was conservative. For modeling ambient growth for the full
build out a growth rate of 2.25 percent is appropriate for movements on North 19th Avenue and East Valley Center Road,
and 1.50 percent for all other movements and intersections. Figures 6 and 7 (pages 18 and 19) illustrate the projected AM and
PM peak hour traffic volume projections that were calculated for this study for the Phase 1 (2021) and Full Buildout (2040)
scenarios, respectively.
Intersection Capacity
Sanderson Stewart initially performed peak hour intersection capacity calculations for the Phase 1 (2021) and Full Buildout
(2040) scenarios based on existing lane configurations and traffic control features. The site access intersections were
presumed to be stop-controlled and to have single-lane approaches for the purposes of this analysis with exception of Cattail
Street/North 19th Avenue and North 19th Avenue/E Valley Center Road. Tables 6 and 7 (pages 20-21 and 22-23) show the
results of the Phase 1 (2021) and Full Buildout (2040) scenario capacity calculations, respectively.
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Billings Clinic-Bozeman TIS 20
Table 6: Phase 1 (2021) Capacity Calculations
Avg
Delay
(s/veh) LOS
95th %
Queue
(veh)
Avg
Delay
(s/veh) LOS
95th %
Queue
(veh)
EB 0.0 A 0 0.0 A 0
WB 0.6 A 0 0.1 A 0
NB 14.4 B 1 27.8 D 5
EB 8.8 A 0 9.0 A 0
WB 9.9 A 0 10.6 B 0
NB 0.0 A 0 0.1 A 0
SB 0.2 A 0 0.0 A 0
EB 0.0 A 0 0.0 A 0
WB 0.0 A 0 0.0 A 0
NB 11.5 B 0 13.8 B 0
EB 0.0 A 0 0.0 A 0
WB 0.1 A 0 0.2 A 0
NB 14.1 B 1 17.0 C 2
WB 10.1 B 1 10.9 B 1
NB 0.0 A 0 0.0 A 0
SB 0.2 A 0 0.5 A 0
EB 10.1 B 1 11.0 B 1
WB 10.3 B 1 12.3 B 1
NB 0.6 A 0 0.9 A 0
SB 0.0 A 0 0.1 A 0
EB 10.3 B 1 11.8 B 1
WB 15.1 C 1 18.6 C 1
NB 1.1 A 1 1.6 A 1
SB 0.0 A 0 0.2 A 0
EB 11.2 B 1 13.8 B 2
WB 10.9 B 1 16.5 C 3
NB 0.7 A 0 1.4 A 0
SB 1.8 A 0 2.1 A 1
Catamount Street &
E Valley Center Road
Intersection Control Two-Way Stop Controlled (EB/WB)
Catron Street &
North 27th Avenue
Davis Lane &
Catamount Street
Intersection Control Two-Way Stop Controlled (EB/WB)
Catamount Street &
North 27th Avenue
Intersection Control Two-Way Stop Controlled (EB/WB)
Westlake Road &
E Valley Center Road
Intersection Control One-Way Stop Controlled (NB)
North 27th Avenue &
E Valley Center Road
Intersection Control One-Way Stop Controlled (WB)
Davis Lane &
E Valley Center Road
Intersection Control Two-Way Stop Controlled (EB/WB)
Davis Lane &
Westlake Road
Intersection Control One-Way Stop Controlled (NB)
Intersection Control One-Way Stop Controlled (NB)
Intersection Approach
Phase 1 (2021)
AM Peak PM Peak
Billings Clinic-Bozeman TIS 21
Table 6: Phase 1 (2021) Capacity Calculations cont.
Avg
Delay
(s/veh) LOS
95th %
Queue
(veh)
Avg
Delay
(s/veh) LOS
95th %
Queue
(veh)
EB 13.3 B 1 26.5 D 3
WB 12.7 B 1 28.8 D 3
NB 0.0 A 0 0.2 A 0
SB 0.2 A 0 0.1 A 0
EB 10.3 B 1 10.8 B 1
NB 1.7 A 1 3.9 A 1
SB 0.0 A 0 0.0 A 0
EB 28.7 C 2 49.8 D 6
WB 46.4 D 1 77.4 E 5
NB 10.2 B 11 18.8 B 22
SB 11.0 B 13 20.2 C 21
Intersection 13.7 B -- 25.6 C --
EB 42.4 D 20 59.8 E 28
WB 31.6 C 1 39.7 D 2
NB 34.8 C 8 75.2 E 14
SB 22.8 C 13 27.8 C 11
Intersection 31.5 C -- 53.0 D --
EB 0.0 A 0 0.0 A 0
WB 5.8 A 1 1.7 A 1
NB 12.4 B 1 14.2 B 2
EB 8.5 A 1 8.8 A 1
NB 6.2 A 1 1.9 A 1
SB 0.0 A 0 0.0 A 0
North 27th Avenue &
Site Access
E Valley Center Road &
Street B
Intersection Control One-Way Stop Controlled (EB)
Cattail Street &
North 19th Avenue
Intersection Control One-Way Stop Controlled (NB)
Intersection Control Signalized
North 19th Avenue &
E Valley Center Road
Davis Lane &
Cattail Street
Intersection Control One-Way Stop Controlled (EB)
Cattail Street &
North 27th Avenue
Intersection Control Signalized
Intersection Control Two-Way Stop Controlled (EB/WB)
Intersection Approach
Phase 1 (2021)
AM Peak PM Peak
Billings Clinic-Bozeman TIS 22
Table 7: Full Buildout (2040) Capacity Calculations
Avg
Delay
(s/veh) LOS
95th %
Queue
(veh)
Avg
Delay
(s/veh) LOS
95th %
Queue
(veh)
EB 0.0 A 0 0.0 A 0
WB 0.6 A 0 0.2 A 0
NB 33.9 D 5 1552.1 F 94
EB 9.2 A 0 9.3 A 0
WB 11.2 B 1 12.6 B 1
NB 0.0 A 0 0.0 A 0
SB 1.1 A 1 0.4 A 0
EB 0.0 A 0 0.0 A 0
WB 5.6 A 1 1.9 A 1
NB 17.3 C 1 21.6 C 3
EB 0.0 A 0 0.0 A 0
WB 1.5 A 1 0.9 A 1
NB 21.1 C 1 237.7 F 24
EB 12.5 B 1 14.8 B 1
WB 13.1 B 1 15.9 C 1
NB 0.0 A 0 0.0 A 0
SB 0.2 A 0 0.4 A 0
EB 15.1 C 2 17.4 C 3
WB 16.6 C 1 24.6 C 3
NB 2.7 A 1 2.0 A 1
SB 0.3 A 0 0.3 A 0
EB 14.0 B 2 23.5 C 3
WB 63.3 F 4 147.4 F 6
NB 1.3 A 1 1.8 A 1
SB 0.0 A 0 0.2 A 0
EB 16.8 C 2 33.6 D 5
WB 15.2 C 1 296.4 F 33
NB 0.5 A 0 1.1 A 1
SB 1.3 A 1 1.6 A 1
EB 22.0 C 2 629.8 F 31
WB 19.7 C 2 868.4 F 39
NB 0.0 A 0 0.2 A 0
SB 0.2 A 0 0.1 A 0
EB 14.4 B 2 17.4 C 2
NB 1.0 A 1 3.4 A 1
SB 0.0 A 0 0.0 A 0
One-Way Stop Controlled (EB)
Cattail Street &
North 27th Avenue
Intersection Control One-Way Stop Controlled (NB)
Intersection Approach
Full Buildout (2040)
AM Peak PM Peak
Davis Lane &
E Valley Center Road
Intersection Control Two-Way Stop Controlled (EB/WB)
Davis Lane &
Westlake Road
Intersection Control One-Way Stop Controlled (NB)
Westlake Road &
E Valley Center Road
Intersection Control One-Way Stop Controlled (WB)
Intersection Control One-Way Stop Controlled (NB)
North 27th Avenue &
E Valley Center Road
Davis Lane &
Catamount Street
Intersection Control Two-Way Stop Controlled (EB/WB)
Catamount Street &
North 27th Avenue
Intersection Control Two-Way Stop Controlled (EB/WB)
Two-Way Stop Controlled (EB/WB)
Catron Street &
North 27th Avenue
Intersection Control Two-Way Stop Controlled (EB/WB)
Catamount Street &
E Valley Center Road
Intersection Control
Davis Lane &
Cattail Street
Intersection Control
Billings Clinic-Bozeman TIS 23
Table 7: Full Buildout (2040) Capacity Calculations cont.
Avg LOS 95th % Avg LOS 95th %
EB 28.3 C 4 35.3 D 11
WB 45.9 D 2 76.6 E 8
NB 19.0 B 22 50.9 D 52
SB 18.4 B 27 85.6 F 45
Intersection 20.6 C -- 61.4 E --
EB 141.3 F 40 299.9 F 56
WB 30.8 C 1 41.0 D 3
NB 64.6 E 13 183.9 F 27
SB 40.7 D 22 72.2 E 19
Intersection 75.2 E -- 173.3 F --
WB 11.4 B 1 15.7 C 3
NB 0.0 A 0 0.0 A 0
SB 4.8 A 1 4.5 A 1
EB 10.2 B 1 11.7 B 1
WB 13.3 B 1 13.1 B 1
NB 3.7 A 1 1.6 A 1
SB 0.0 A 0 0.0 A 0
EB 10.1 B 1 10.8 B 1
WB 16.6 C 1 18.6 C 1
NB 0.8 A 1 0.4 A 1
SB 0.2 A 0 0.2 A 0
EB 0.0 A 0 0.0 A 0
WB 2.5 A 1 0.8 A 1
NB 16.8 C 1 19.8 C 2
WB 11.2 B 1 12.5 B 1
NB 0.0 A 0 0.0 A 0
SB 2.0 A 1 0.8 A 1
EB 10.8 B 1 12.4 B 2
NB 6.5 A 1 2.4 A 1
SB 0.0 A 0 0.0 A 0
EB 3.6 A 1 1.2 A 0
WB 0.5 A 0 3.6 A 1
NB 9.3 A 1 10.4 B 1
SB 11.1 B 1 13.1 B 2
EB 0.0 A 0 0.0 A 0
WB 3.8 A 1 2.5 A 1
NB 9.5 A 1 10.1 B 1
EB 0.0 A 0 0.0 A 0
WB 6.2 A 1 2.6 A 1
NB 9.3 A 1 9.5 A 1
Intersection Control Signalized
Two-Way Stop Controlled (NB/SB)
One-Way Stop Controlled (EB)
One-Way Stop Controlled (WB)
One-Way Stop Controlled (NB)
Intersection Approach
Full Buildout (2040)
AM Peak PM Peak
Intersection Control One-Way Stop Controlled (WB)
Cattail Street &
N 27th Avenue Extension
Intersection Control
North 27th Avenue &
Site Access
Intersection Control
Intersection Control
Cattail Street &
North 19th Avenue
Intersection Control
E Valley Center Road &
Street B
Intersection Control
Signalized
North 19th Avenue &
E Valley Center Road
Westlake Road &
West Site Access
Intersection Control Two-Way Stop Controlled (EB/WB)
North 27th Avenue &
Honor Lane
Intersection Control Two-Way Stop Controlled (EB/WB)
E Valley Center Road &
Honor Lane
Intersection Control One-Way Stop Controlled (NB)
Westlake Road &
East Site Access
Intersection Control One-Way Stop Controlled (NB)
Catamount Street &
Warbler Way/Site Access
Davis Lane &
Site Access
Billings Clinic-Bozeman TIS 24
Mitigation Alternatives
Sanderson Stewart evaluated a variety of potential mitigation improvement options to address projected impacts for study area
streets and intersections. The following paragraphs provide details on that analysis.
The Bozeman TMP recommends improvements to several streets and intersections in the study area. Corridor improvement
recommendations include:
1. East Valley Center Road widened to a three-lane urban principal arterial standard west of North 27th Avenue
2. Davis Lane widened to a five-lane urban minor arterial standard between Baxter Lane and East Valley Center Road
3. North 27th Avenue widened to a three-lane urban collector standard between Baxter Lane and East Valley Center
Road
4. Cattail Street widened to a three-lane urban collector between Davis Lane and Harper Puckett Road and between
North 19th Avenue and North 27th Avenue
5. Catamount Street improvements from North 27th Avenue to Valley Center Road to a two- lane urban minor arterial
standard
Intersection improvements recommended in the Bozeman TMP include:
1. Installation of a single-lane roundabout or traffic signal (with additional geometric improvements) when warrants are
met at the intersections of Davis Lane/Catamount Street and Davis Lane/Cattail Street
2. Installation of a traffic signal when warrants are met at the intersection of Davis Lane/East Valley Center Road, with
a recommended lane configuration to include northbound left and right-turn bays, a westbound left-turn bay, and an
eastbound right-turn lane
3. Installation of a traffic signal at North 27th Avenue/Valley Center Road (with additional geometric improvements)
when warrants are met, with potential lane configuration modifications including the addition of an eastbound right-
turn lane
Pedestrian/bicycle improvements recommended in the Bozeman TMP include:
1. Installation of a crosswalk and Rectangular Rapid Flashing Beacons (RRFB) at the intersection of Davis Lane/Cattail
Street
2. Installation of bike lanes on North 19th Avenue south of East Valley Center Drive
3. Installation of a shared use path along East Valley Center Drive between North 19th Avenue and Catamount Street
None of these improvement projects are designed or programmed for construction as of this writing. As such, the baseline
condition for analysis was that the improvements will not be in place by 2040. However, the recommended project
improvements were considered as potential mitigation alternatives through our analysis.
Auxiliary turn lane warrants were evaluated for study area intersections that exhibited peak hour intersection capacity
deficiencies and/or high turning movement demands for the Existing Conditions (2020), Phase 1 (2021), and Full Buildout
(2040) scenarios. The analysis was completed using the methodology outlined in MDT’s Traffic Engineering Manual
(November 2007). Table 8 on the following page shows the results of the analysis for the study area intersections where
auxiliary turn lane warrants were found to be met. Auxiliary turn lane warrant worksheets for those intersections are included
in Appendix E. Additionally, it is recommended in the Bozeman TMP that auxiliary left-turn and right-turn lanes be
Billings Clinic-Bozeman TIS 25
constructed on the northbound approach at the intersection of Davis Lane/East Valley Center Road, a westbound left-turn
lane bay and eastbound right-turn lane as a future capital improvements project. Our analysis also confirms a warranted
eastbound right-turn lane at Davis Lane/East Valley Center Road for existing conditions. With Phase 1 projections a
westbound left-turn lane is warranted at the intersection of East Valley Center Road/Street B (site access).
Traffic signal warrants were also evaluated for the four unsignalized study area intersections experiencing LOS deficiencies
based on Full Buildout (2040) scenario traffic volume projections using the criteria outlined in the Manual on Uniform Traffic
Control Devices (MUTCD). The MUTCD presents several warrants that can be considered based on traffic volumes, school
crossings, crash history, and other considerations. For the purposes of this analysis, all but Warrants 4, 5, and 9 (Pedestrian
Volume, School Crossing, and Intersection Near a Grade Crossing) were evaluated. Those warrants were not evaluated
because there are no schools or railroad crossings near the site, and pedestrian demand at the intersections are very light even
during peak hours compared to what would be required to meet the warrant. The results of the traffic signal warrant analyses
are shown in Table 9 on page 27. Traffic signal warrant worksheets for the Full Buildout (2040) scenario are included in
Appendix E.
The traffic signal warrants analysis results showed that three of the volume-based traffic signal warrants are projected to be
met for the intersections of East Valley Center Road with Davis Lane, North 27th Avenue and Catamount Street for the Full
Buildout (2040) scenario. However, for the East Valley Center Road/Catamount Street intersection, a majority (nearly 95%)
of the traffic demand on the higher-volume minor (eastbound) approach are right-turn movements. Although there is not
currently an auxiliary right-turn bay on that approach now, the addition of a dedicated right-turn lane would invoke the
subjective question of whether or not the eastbound right-turn movement demands should be included in the warrant analysis.
The MUTCD directs that the engineer should use discretion in this determination based on whether or not a right-turn
movement in a dedicated lane can be made with “low conflict.” In prior studies completed for and by MDT, when this
situation has arisen, the typical approach has been to evaluate warrants under three conditions: 1) with no reduction in right
AM PM AM PM AM PM AM PM AM PM AM PM
EB Right-Turn Lane YES YES NO NO
EB Left-Turn Lane
WB Right-Turn Lane
WB Left-Turn Lane NO NO
NB Right-Turn Lane NO NO NO NO
NB Left-Turn Lane NO NO
SB Right-Turn Lane NO NO NO NO
SB Left-Turn Lane NO NO
EB Right-Turn Lane YES YES NO NO NO NO
EB Left-Turn Lane
WB Right-Turn Lane
WB Left-Turn Lane NO NO YES YES
NB Right-Turn Lane NO NO NO YES
NB Left-Turn Lane NO NO NO NO
SB Right-Turn Lane NO NO NO NO NO NO
SB Left-Turn Lane NO NO
EB Right-Turn Lane YES YES YES YES YES NO
EB Left-Turn Lane
WB Right-Turn Lane
WB Left-Turn Lane NO NO YES NO
NB Right-Turn Lane NO NO NO YES
NB Left-Turn Lane NO NO NO NO
SB Right-Turn Lane NO NO NO YES NO NO
SB Left-Turn Lane NO NO
TURN LANE WARRANTS
Davis Lane &
E Valley Center Rd
N 27th Ave &
Site Access
2021
2040
2020
E Valley Center Rd &
Catamount Street
Davis Lane &
Cattail Street
N 27th Ave &
E Valley Center Rd
E Valley Center Rd &
Street B
Table 8: Full Buildout (2040) Auxiliary Turn Lane Warrant Summary
Billings Clinic-Bozeman TIS 26
turns; 2) with a 50% reduction in right turns; and 3) with a 100% reduction in right-turns. For the East Valley Center
Road/Catamount Street intersection, the complete removal of right-turns would result in very few of the MUTCD traffic
signal warrants being met, but with no reduction and even 50% reduction of right-turn movements, the four and eight-hour
volumes would meet warrants. In this case, given that the warrants are met for four and eight-hour future projected traffic
demand, Sanderson Stewart would consider that the volume-based traffic signal warrants would be met for the East Valley
Center Road/Catamount Street intersection.
Only the Peak Hour warrant is projected to be met for the intersection of Davis Lane and Cattail Street. The Peak Hour
warrant is generally intended for application for intersections near a facility that discharges a high volume of traffic in a very
short duration (such as a school or a factory with shift-based operations). As such, most jurisdictions are hesitant to install a
traffic signal on the basis of only the Peak Hour warrant being met unless those special conditions exist, which in this case,
they do not. Therefore, although the Peak Hour warrant is projected to be met, Sanderson Stewart does not consider traffic
signal warrants to be met for the Davis Lane/Cattail Street intersection.
Since multiple traffic signal warrants are projected to be met for the East Valley Center Road/Davis Lane intersection for the
Full Buildout (2040) analysis scenario, Sanderson Stewart performed signalized intersection capacity calculations for that
intersection to gauge performance of those potential improvements and to evaluate lane configurations and signal phasing that
would be appropriate for the intersections with signalized control. The calculations results showed that traffic signals with
basic two-phased, semi-actuated control and existing lane configurations would result in LOS B or better operations on all
approaches for the intersection. Sanderson Stewart also evaluated roundabout operations for the intersection with the analysis
results showing the intersection would operate well as a single-lane roundabout. All approaches were predicted to be
operating at LOS A in AM peak hour and all approaches in PM peak hour would operate at LOS A with exception of
eastbound East Valley Center Road, which would operate at LOS C.
As was previously reported, traffic signal warrants are met based on Design Year (2040) traffic volume projections for the
intersection of East Valley Center Road and Catamount Street with 100% and 50% of reported right-turns. No auxiliary turn
lane improvements are projected to be warranted for that intersection, but an eastbound (minor approach) right-turn bay may
be advisable due to the high demand for that movement. Projected turning movement volumes are not well-balanced between
the mainline and minor approaches, so all-way stop control would likely not be an appropriate fix, except possibly as a short-
term interim solution. Intersection capacity calculations did show that a single-lane roundabout would operate very well at the
intersection, resulting in all approaches operating at LOS A. It is also expected that a traffic signal with semi-actuated control
to give substantial priority to mainline traffic would also operate very well for this intersection.
Traffic signal warrants are also not considered to be met based on Design Year (2040) traffic volume projections for the
intersection of Davis Lane and Cattail Street. The addition of warranted auxiliary northbound and southbound right-turn
lanes for the intersection is also not projected to substantially improve peak hour LOS conditions. The Bozeman TMP
recommended the widening of Davis Lane to a five-lane urban section, which was modeled and found to provide little
improvement to capacity/LOS conditions, with the minor legs still experiencing LOS E and F during the PM peak hour. Here
again, projected turning movement volumes are not well-balanced between the mainline and minor approaches, so all-way
stop control would likely not be an appropriate fix, except possibly as a short-term interim solution. Intersection capacity
calculations showed that a single-lane roundabout would operate very well at the intersection as well, resulting in all
approaches operating at LOS A with exception to southbound PM peak traffic on Davis Lane, operating at LOS B. It is also
expected that a traffic signal with semi-actuated control to give substantial priority to mainline traffic would also operate very
well for this intersection.
Billings Clinic-Bozeman TIS 27
The signalized intersection of North 19th Avenue and Cattail Street is projected to experience substandard LOS during the
AM and PM peak hours. Several timing and phasing alternatives were evaluated to assess whether they would improve LOS
and queuing. One alternative was to alter the west (eastbound) approach to provide a dedicated right-turn bay (thereby
separating left-turn, thru, and right-turn movements), and to implement a right-turn overlap phase for that approach. Doing so
improved operational metrics considerably, particularly for the eastbound approach, but the intersection as a whole and two of
the four approaches are still projected to operate at LOS D during the PM peak hour. Only the addition of thru lanes on the
northbound and southbound approaches is projected to improve overall AM peak hour capacity to LOS C and LOS D for
PM peak hour. However, even those minor improvements in LOS that would require an extensive lane expansion/corridor
widening project for the North 19th Avenue corridor.
The signalized intersection of North 19th Avenue and East Valley Center Road is projected to experience substandard LOS
during the AM and PM peak hours. Several timing and phasing alternatives were evaluated to assess whether they would
improve LOS and queuing. One alternative was to alter the west (eastbound) approach to provide two eastbound left-turn
bays (thereby separating left-turn, thru, and right-turn movements). Doing so improved operational metrics particularly during
the AM peak hour and for the intersection as a whole during the AM and PM peak hours, though three of the four approaches
are still projected to operate at LOS D or E during the PM peak hour.
The intersection capacity calculation results for the above-described mitigation improvement analyses are summarized in Table
10 on the following page. Detailed capacity calculation worksheets for these scenarios, as well as the calculation worksheets
with warranted turn lanes modeled, are included in Appendix F.
CONCLUSIONS & RECOMMENDATIONS
Conclusions
The preceding analysis has shown that the Billings Clinic-Bozeman site development project will generate a substantial volume
of new traffic demand for area streets and intersections once the subdivision is fully developed. The conceptual development
plan proposes construction of approximately 695,250 square-feet of medical office and hospital facilities, 100,000 square-feet
of commercial space, and 94 apartment-style residential dwelling units. A multi-level parking garage and a public transit station,
as well as development of 9.5 acres of park/open space is also proposed. Full buildout and occupancy of the entire project is
projected for completion by approximately 2040. The proposed land uses associated with Phase 1 of the project (medical
x x
x
x
-- -- -- -- -- --
-- -- -- -- -- --
x x x x x x
x x x x x x
x
-- -- -- -- -- --
Yes
No x x
8. Roadway Network
Signals Warranted
1. Eight-Hour Vehicular Volume
2. Four-Hour Vehicular Volume
3. Peak Hour
4. Pedestrian Volume
5. School Crossing
6. Coordinated Signal System
7. Crash History
9. Intersection Near a Grade Crossing
East Valley Center Road
& Catamount Street
(100% EB RTs)
Davis Lane
& Cattail Street
E Valley Center Road
& Davis Lane
Full Buildout (2040)
TRAFFIC SIGNAL WARRANTS East Valley Center Road
& Catamount Street
(50% EB RTs)
East Valley Center Road
& Catamount Street
(0% EB RTs)
E Valley Center Road
& N 27th Ave
Table 9: Full Buildout (2040) Traffic Signal Warrant Summary
Billings Clinic-Bozeman TIS 28
Avg
Delay
(s/veh) LOS
95th %
Queue
(veh)
Avg
Delay
(s/veh) LOS
95th %
Queue
(veh)
EB 7.8 A 12 15.4 B 13
WB 3.7 A 3 12.1 B 14
NB 12.8 B 5 16.8 B 7
Intersection 12.8 B -- 14.4 B --
EB 9.2 A 6 7.4 A 4
WB 4.9 A 1 16.7 C 11
NB 7.9 A 2 9.7 A 3
Intersection 8.3 A -- 11.6 B --
EB 5.2 A 6 7.6 A 10
WB 4.7 A 4 6.7 A 7
NB 12.5 B 2 14.1 B 5
Intersection 5.4 A -- 8.6 A --
EB 8.1 A 4 8.1 A 4
WB 6.6 A 3 9.3 A 4
NB 5.7 A 1 10.2 B 3
Intersection 7.3 A -- 9.0 A --
Intersection Control
EB 10.5 B 2 13.1 B 2
WB 9.3 A 2 11.5 B 2
NB 5.5 A 3 5.3 A 3
SB 5.4 A 3 4.9 A 3
Intersection 6.2 A -- 6.1 A --
Intersection Control
EB 7.1 A 1 7.8 A 1
WB 5.6 A 1 6.0 A 1
NB 4.8 A 2 5.6 A 2
SB 5.5 A 2 6.4 A 2
Intersection 5.4 A -- 6.1 A --
Intersection Control
EB 8.4 A 3 13.0 B 6
WB 8.2 A 2 13.1 B 6
NB 6.9 A 5 7.6 A 10
SB 6.4 A 4 6.8 A 8
Intersection 7.1 A -- 8.7 A --
Intersection Control
EB 5.2 A 1 8.1 A 2
WB 5.2 A 1 8.8 A 2
NB 6.4 A 2 10.8 B 5
SB 5.3 A 2 9.4 A 4
Intersection 5.7 A -- 9.7 A --
Intersection Control
EB 32.1 C 4 30.9 C 12
WB 38.1 D 3 41.0 D 6
NB 40.8 D 9 46.5 D 18
SB 19.9 B 12 23.8 C 21
Intersection 30.4 C -- 36.8 D --
Intersection Control
EB 48.4 D 13 40.4 D 17
WB 34.8 C 2 62.2 E 2
NB 21.2 C 7 8.4 A 12
SB 31.1 C 14 50.2 D 15
Intersection 33.5 C -- 33.5 C --
Davis Lane &
Cattail Street
East Valley Center Road &
Davis Lane
Intersection Control Approach
Full Buildout (2040) Improved
AM Peak PM Peak
Intersection Control Signalized
Intersection Control Roundabout
East Valley Center Road &
Davis Lane
Intersection Control Signalized
East Valley Center Road &
North 27th Avenue
Intersection Control Roundabout
East Valley Center Road &
North 27th Avenue
East Valley Center Road &
Catamount Street
East Valley Center Road &
Catamount Street
Davis Lane &
Cattail Street
Addition of 2 EB left-turn bays, NB/SB thru lanes
North 19th Avenue &
East Valley Center Road
North 19th Avenue &
Cattail Street
Signalized
Roundabout
Signalized
Roundabout
Addition of EB right & left-turn bays, NB/SB thru lanes
Table 10: Full Buildout (2040) – Improved Capacity Calculations
Billings Clinic-Bozeman TIS 29
office and ambulatory surgery facilities) would account for approximately 20-25% of the full buildout trip generation with a
projected buildout and occupancy time frame of late 2021.
The Existing Conditions (2020) traffic scenario analysis showed that all study area non-signalized intersections currently
operate at LOS C or better during both peak periods. Cattail Street/North 19th Avenue and North 19th Avenue/East Valley
Center Road both predict LOS D or E on east and west bound approaches during the AM and PM peak hours. North 19th
Avenue and East Valley Center Road intersection also has queueing on the northbound approach in the PM peak hour.
Although the intersections have no delay deficiencies, there is an eastbound right-turn lane warranted during the PM peak
hour at the intersection of Davis Lane/East Valley Center Road for Existing Conditions (2020).
The crash and severity rates for the existing study area intersections were found to be identical to or less than HSM predicted
rates, implying that from a crash frequency standpoint, there may not be any particularly concerning trends or patterns within
the study area. The analysis results did show a high number of rear end crashes reported at the intersection of North 19th
Avenue/Cattail Street, which could be caused in part by relatively high speeds (40 mph) in the corridor, or inadequate yellow
change intervals (as compared with ITE-recommended design values), or other factors less controllable such as poor roadway
conditions during inclement weather periods.
Phase 1 development is expected to be complete by the end of 2021. An analysis of projected intersection capacity for the
Phase 1 (2021) traffic projection scenario showed that most study area unsignalized intersections would operate at LOS C or
better during both the AM and PM peak hour periods. The exceptions to this were Davis Lane at East Valley Center Road,
which had a PM peak queue in the northbound direction, and Davis Lane/Cattail Street, which had a PM peak LOS D on the
east and westbound approaches. Both existing signalized intersections at Cattail Street/North 19th Avenue and East Valley
Center Road/North 19th Avenue had east and westbound delays (LOS D or E) in the AM and/or PM peak hours, with the
latter intersection also having PM peak delays in the northbound direction. There were several warranted auxiliary turn lanes
at study area intersections for Phase 1 year (2021). The intersection of Davis Lane/East Valley Center Road had an eastbound
right-turn lane warranted during both peak hours and at Davis Lane/Cattail Street a northbound right-turn lane was warranted
from PM peak hour. At East Valley Center Road/Street B (site access) a left-turn lane was warranted from both AM and PM
peak hours. Implementation of those turn lanes with proper geometric design would further improve operational conditions
and would likely augment safety conditions as well.
Full buildout and occupancy of the Billings Clinic-Bozeman development is projected to be complete by approximately 2040.
An analysis of Full Buildout (2040) scenario intersection capacity showed that substandard LOS and queuing conditions are
expected for multiple approaches at four (currently) unsignalized and two signalized study area intersections. An evaluation of
auxiliary turn lane and traffic signal warrants for study area intersections showed that a traffic signal is projected to be
warranted for the intersection of East Valley Center Road/Davis Lane, East Valley Center Road/North 27th Avenue and East
Valley Center Road/Catamount Street. Sanderson Stewart does not consider a traffic signal to be warranted for the
intersection of Davis Lane with Cattail Street though it is projected to have substantial capacity deficiencies during PM peak
traffic periods on the east and west bound approaches. Additional auxiliary turn lanes were shown to be need for the Design
Year (2040) scenario. The intersection of Davis Lane/Cattail Street had northbound and southbound right-turn lanes
warranted during the PM peak hour, and North 27th Avenue and East Valley Center Road had a warranted right lane in AM
and PM peak hour. The proposed intersection of East Valley Center Road with Street B was projected to warrant a
westbound left-turn lane in the PM peak hour and a right-turn lane for AM peak hour. Implementation of those turn lanes
with proper geometric design would further improve operational conditions and would likely augment safety conditions as
well.
Billings Clinic-Bozeman TIS 30
Additional Design Year (2040) intersection capacity calculations were performed for select intersections to gauge the impacts
of geometric and traffic control improvements. It was found that the warranted turn lanes had little effect on capacity at the
failing intersection approaches but that implementing traffic signals or roundabouts would improve capacity to an acceptable
LOS at the intersections of East Valley Center Road/Davis Lane, East Valley Center Road/Catamount Street, and Davis
Lane/Cattail Street (noting again that the latter intersection is not projected to have traffic signal warrants be met). The
recommended reconstruction of Davis Lane to a five-lane arterial section was also implemented as part of the Full Buildout
(2040) mitigation improvements capacity analysis, but the additional lanes on the major street were found to have little
improvement on minor approach LOS.
To mitigate the deficiencies at the signalized intersection of North 19th Avenue/Cattail Street and North 19th Avenue/East
Valley Center Road, Sanderson Stewart looked at modifications to lane configurations and traffic signal timing and phasing
plans. However, those types of improvements alone did not provide LOS C or better metrics on all approaches during peak
traffic periods. In order to achieve that standard, it was necessary to model a third thru travel lane on North 19th Avenue for
both northbound and southbound traffic. However, this plan would require major road reconstruction in the North 19th
Avenue corridor.
The site access intersections on East Valley Center Road, North 27th Avenue, Davis Lane, and Catamount Street are
anticipated to operate at acceptable levels of service with minimal queuing when modeled with single ingress/egress lanes for
all approaches for both Phase 1 (2021) and Full Buildout (2040) scenarios.
Recommendations
The following list of recommendations (organized in Phase 1 and Full Buildout categories) is based on the analysis results
from this study and the professional judgment of the author:
Phase 1
- Stop signs (R1-1) should be installed for all private site access approaches on public streets.
- A westbound auxiliary left-turn lane should be designed and constructed for the intersection of Street B/East Valley
Center Road.
- An eastbound auxiliary right-turn lane could be reviewed by the city for the intersection of East Valley Center Road
and Davis Lane. The auxiliary lane is warranted based on Existing Conditions (2020) traffic volumes as well as for
future scenarios but does not need to be built out now. Future contribution calculations could be performed as
needed.
- Northbound and southbound auxiliary right-turn lanes should be designed and constructed for the intersection of
Davis Lane and Cattail Street or a roundabout should be considered. They are warranted based on Phase 1 conditions
(2021) traffic volumes. These improvements are consistent with the city’s TMP.
- Sidewalk and/or multi-use path improvements should be constructed along Phase 1 development frontages with off-
site connections to existing facilities also planned to provide for system connectivity wherever possible.
- If the build out of any of these improvements is at the same time as Phase 1 then contribution calculations for
contribution percentages could be calculated, otherwise it could be revisited by the CIP. These improvements are
consistent with the city’s TMP and CIP.
Billings Clinic-Bozeman TIS 31
- All transportation-related improvements shall be designed in accordance with City of Bozeman standards and the
Manual on Uniform Traffic Control Devices (MUTCD).
Full Buildout
For the full buildout, improvements shall be revisited at time of future development. If these items are in the Bozeman TMP
or the City’s CIP then improvements could be implemented sooner.
- Stop signs (R1-1) should be installed for all private site access approaches public streets.
- The following modifications to signal timing/phasing and lane configurations should be considered for the North
19th Avenue/Cattail Street intersection:
o Shorter-term, the addition of an eastbound auxiliary right-turn bay with protected right-turn overlap phasing
would substantially improve operations on that approach and allow for more allocation of green time to the
mainline phases.
o Longer-term, North 19th Avenue will require additional northbound and southbound thru lanes in order to
provide LOS C or better peak hour operations. Planning for right-of-way needs and programming of
funding should be initiated now since this would represent a major corridor reconstruction project.
o A northbound dual left-turn lane configuration is also likely to be necessary at some point in the future based
on Design Year (2040) traffic projections. This improvement would also require a second receiving lane on
Cattail Street to the west of the intersection.
- The intersections that warrant a right-turn lane: Davis Lane/East Valley Center Road (eastbound), Davis/Cattail
Street (both northbound and southbound), North 27th Avenue/East Valley Center Road (eastbound and westbound)
and North 27th Avenue and the site access.
- A left-turn lane is warranted at full build out for East Valley Center Road and the Street B (site access, westbound).
- A traffic signal or roundabout should be programmed for design and construction for the intersections of East Valley
Center Road/Davis Lane and East Valley Center Road/Catamount Street.
- Traffic demand growth should be monitored for the intersection of Davis Lane/Cattail Street to determine if and
when intersection traffic control improvements (signal or roundabout) are warranted and/or necessary to maintain
safe and efficient operations.
- One or more internal intersections may require traffic control improvements as development progresses. Additional
analyses should be performed in the future to evaluate on-site lane configuration and traffic control needs based on
traffic volume demand conditions and the final street and intersection layout for the subdivision.
- Sidewalk and/or multi-use path improvements should be constructed as consistent with recommendations in the
Bozeman Transportation Master Plan (2017).
- All transportation-related improvements shall be designed in accordance with City of Bozeman standards and the
Manual on Uniform Traffic Control Devices (MUTCD).