Idaho 55 / Banks Lowman Road Intersection Study

The intersection of State Highway 55 and Banks Lowman Road is located approximately 41 miles north of Boise and provides access to a variety of recreational opportunities in the surrounding public lands. On weekends during the summer, the area experiences an influx of recreational traffic resulting in congestion and lengthy delays for vehicles along Banks Lowman Road. During busy days, the Idaho Transportation Department (ITD) has implemented temporary flagging control to help control and alleviate congestion. As traffic volumes continue to increase, however, the existing strategy is inadequate to meet the growing demands at the intersection.

After collecting traffic data and observing vehicle queuing and turning movements in the field, RPA used a multi-step approach to evaluate existing and projected traffic conditions, including both deterministic and microsimulation analyses. To address operational and safety conditions at the site, RPA analyzed multiple alternatives included maintaining the existing two-way stop control, implementing flagging control more frequently, installing a traffic signal, and installing a single-lane roundabout.

While the existing stop control and peak day flagging operation is viable in the short term, the configuration is not sustainable for the long-term. The flagging operation is shown to help alleviate existing congestion concerns, however, the option offers minor capacity increases and would need to be implemented more frequently during the peak season. Automated flagging control was identified as an interim solution while designs for a more permanent solution are developed. Based on the results of the evaluation process, a traffic signal was identified as the preferred alternative for the intersection. Compared to the other traffic control scenarios, the roundabout was shown to provide the lowest capacity and shortest anticipated life. Conversely, the traffic signal provides the greatest life of all alternatives and the best operational performance under future growth scenarios.

Gallatin County has experienced significant growth over the past 40 years. The county has consistently outpaced the population growth of other Montana counties. This growth can be attributed to the evolving economies of the county’s largest cities, Bozeman and Belgrade, the continued expansion of Montana State University in Bozeman, and in-migration resulting from the high quality of life that the county offers. As Gallatin County continues to grow, it is important to understand growth trends to properly accommodate and prepare for the county’s current and future transportation needs.

The last regional county transportation plan was completed in 2007 with more recent updates completed for the urban areas of Bozeman and Belgrade. A new, comprehensive look at the transportation system in the growing suburban area was needed to understand system needs and investment opportunities over the next 20 years.

The Greater Triangle Area Transportation Plan (GTATP) provides a comprehensive and integrated strategy for transportation infrastructure and service improvements within the greater triangle area between Bozeman, Belgrade, Four Corners, and Gallatin Gateway. The GTATP focuses on strengthened roadway connections to facilitate safe and efficient travel between these quickly growing communities within the county. The plan addresses regional transportation issues, overall travel convenience, traffic safety, sustainability, funding, and multimodal connections. The GTATP includes recommendations for short-term improvements as well as long-term modifications and capital improvements to major roadways.

The GTATP serves as a guide for development of and investment in the region’s transportation system in a comprehensive manner. The GTATP was developed through a collaborative approach with county, state, and city staff, elected officials, and local residents. The plan provides a blueprint for guiding transportation infrastructure investments based on system needs and associated decision-making principles. The GTATP integrates previously completed planning efforts, includes detailed analysis of existing and projected transportation conditions, incorporates meaningful input from citizens and local officials, and provides a framework for future efforts within the context of state and federal rules, regulations, and funding allocations.

US Highway 93 (US 93) is an important highway corridor and supports local, regional, and nationwide transportation. The Ninepipe segment extends from Reference Post (RP) 40.0 to 44.5 south of Ronan, MT in Mission Valley. The corridor is situated in a highly sensitive ecological and cultural environment through federal and tribal lands designated for wildlife management, environmental protection, and cultural preservation. Improvements to the corridor are needed to address poor existing traffic operations, projected increases in traffic volumes, multiple safety concerns, and a lack of dedicated pedestrian and bicycle facilities.

Building from an alternative identified in previous environmental documentation, RPA worked collaboratively with the Montana Department of Transportation (MDT), the Confederated Salish and Kootenai Tribes (CSKT), and multiple environmental resource agencies to identify a feasible reconstruction concept that would optimize benefits and reduce impacts. The study evaluated geotechnical constraints, hydraulic considerations, wetland impacts, cultural influences, and right-of-way needs to evaluate improvement options in terms of impacts, construction costs, and feasibility considerations. Findings from this study will be used to assist MDT in project development decisions and will support a future environmental re-evaluation.

The study area is situated in the heart of Helena and provides access to the Downtown, Capitol, Helena College, and Helena Middle School. The area includes primary commercial, business, and residential districts and serves multiple transportation modes including passenger vehicles, freight, bicycles, pedestrians, transit, and rail. The study corridors and five-point intersections each have unique character, settings, and configurations, each with their own set of issues and needs. The two five-point intersections have non-standard layouts and geometrics. The configurations can cause driver confusion and have poor operating efficiency, particularly during peak hours. The study identified concerns regarding safety, a lack of suitable non-motorized infrastructure, undesirable aesthetics and lack of gateway signage, and access to commercial and residential areas.

The traffic study considered all previously completed planning efforts, assessed existing and projected transportation and environmental conditions, provided an in-depth analysis of feasible improvement options, and identified recommendations to be implemented over the next 20 years. Through a comprehensive evaluation of transportation and environmental conditions and a wide-ranging public and stakeholder outreach process, the traffic study identified a set of 16 recommendations to address multimodal safety, connectivity, access, mobility, aesthetics, wayfinding, and economic vitality for the adjacent areas. The recommended improvements offer a range of potential short- and long-term strategies to address areas of concern, including streetscaping enhancements, sidewalk improvements, ADA curb ramps, enhanced crosswalks, traffic signal timing adjustments, bike lane extensions, intersection realignment, a grade-separated rail crossing, trail extension, and intersection reconstruction.

Extensive public and stakeholder involvement occurred throughout the planning process. Before a study scope was developed, introductory visioning workshops were held with the community and key stakeholders to understand their concerns and needs prior to contract execution. During the plan development, our team held both in-person outreach activities (with small groups, and by appointment) and virtual opportunities. We developed presentation videos, high-quality graphic renderings, and other easy to understand public-facing materials. There was also extensive coordination with MDT, the Downtown Business Improvement District, two TIF districts, adjacent businesses, school district, and the City.