HomeMy WebLinkAbout030_Appendix AC - SUD PH3 Block 3_Arnold & 19th Intersection Memo
851 Bridger Dr., #1, Bozeman, MT 59715 | phone: 406-522-8594
www.seaeng.com
Engineers and Land Surveyors
August 27, 2026
City of Bozeman Engineering Department
20 E. Olive, PO Box 1230
Bozeman, MT 59771-1230
RE: Arnold & 19th Intersection – ¾ Access Determination
Taylor,
The purpose of this memorandum is to summarize the additional information provided by Sanbell
regarding the Traffic Signal Warrant Analysis completed for the Arnold Street and South 19th Avenue
intersection, located at the southwest corner of the SUD Phase 3, Block 3 property.
As discussed during our August 12, 2026 meeting, the additional analysis indicates that restricting the SUD
Phase 3, Block 3 approach at Arnold Street and South 19th Avenue to ¾ access is not warranted at this
time. Sanbell evaluated several additional future-condition scenarios to better understand the operational
effects associated with construction of the Arnold Street connection, development of Block 3, and
potential access restrictions.
The results of the additional intersection operational analyses are summarized in Table 1 below. A brief
discussion of each scenario follows.
Table 1. Future (2031) Arnold Street & South 19th Avenue Operational Analysis
Page | 2
Additional Future-Condition Scenarios
Scenario 3 – No Arnold Street Connection / No Block 3 Development
Operations are very similar to existing conditions.
Scenario 4 – Arnold Street Connection / No Block 3 Development
Operations are very similar to those projected under the full-buildout scenario. Because the number of
trips generated by Block 3 is relatively low, the analysis indicates that the change in intersection
operations is primarily attributable to the addition of the fourth leg of the intersection rather than traffic
generated by Block 3 itself. The four-leg configuration introduces additional conflicts affecting the existing
west leg regardless of whether Block 3 is developed.
Scenario 5 – Eastbound (West Leg) Approach Restricted to ¾ Access
Operations improve because eastbound left-turn movements are eliminated. However, these trips would
be redistributed to the surrounding street network, including potentially to the South 19th Avenue/Stucky
Road intersection.
Scenario 6 – Westbound (East Leg) Approach Restricted to ¾ Access
Operations on the eastbound approach remain generally consistent with the full-access condition because
eastbound left turns remain permitted. Westbound operations improve only marginally due to the
relatively low number of westbound left-turn movements being removed.
Scenario 7 – Effects on South 19th Avenue/Stucky Road and South 19th Avenue/Graf Street
Sanbell also reviewed the potential effects of restricting movements at Arnold Street on the nearby Stucky
Road and Graf Street intersections. Graf Street showed no significant impact is anticipated due to existing
travel patterns and available street connections. Stucky Road showed that restricting eastbound left turns
at Arnold Street could shift additional traffic to Stucky Road, where the eastbound approach is already
projected to operate poorly. Because improvements to Stucky Road are planned, no additional detailed
analysis was completed at this time
Conclusion
Based on Sanbell’s additional analysis and our August 12, 2026 discussion, a ¾-access restriction on the
SUD Phase 3, Block 3 approach at Arnold Street and South 19th Avenue is not warranted at this time. The
Block 3 approach may therefore be designed and constructed as a full-access connection.
Please feel free to contact us with any questions or if additional information is required.
Sincerely,
Jared Fabian, PE
Stahly Engineering & Associates