KLK570 Measures to Alleviate Congestion at Rural Intersections – Case Study: SH-55/Banks-Lowman Hwy Intersection
ITD Research Project 242; Task Order Number UI-14-01
Principal Investigators:
- Ahmed Abdel-Rahim
ITD Project Manager
- Kevin Sablan
FHWA Project Advisor:
- Lance Johnson
Research Problem Statement:
Many state highways experience a surge in traffic flow levels on certain “high-travel” days during the year such as Memorial Day weekend, Thanksgiving holiday, as well as other major seasonal travel activities. This causes excessive delays to vehicles on the minor approach attempting to turn left on to the major highway due to the platooned nature of the high volume traffic traveling on the highway. If the minor approach is also experiencing high levels of traffic demand, vehicles will experience significant congestion and a deteriorated level of service. A typical example of such congestion is at the SH-55/Banks-Lowman Hwy Intersection. During holiday weekends, ITD controls the intersection by flagging operations to allow Banks-Lowman traffic an opportunity to get onto the highway. Without flagger control, there is insufficient available gap side street traffic to enter the highway and traffic backs up for miles resulting in long delays that can lead to motorists’ impatience taking shorter gaps to enter the highway causing safety concerns and potential crashes. During non-holiday summer weekends, recreational traffic has increased to the point where insufficient available gaps is causing extensive side street delays as well as very long queues on Idaho 55.
Project Objectives:
The objective of this project is to investigate measures to alleviate such congestion at rural intersections and recommend a set of measures to Idaho Transportation Department that can reduce congestion and improve the level of service for motorists at SH-55/Banks-Lowman Hwy Intersection as well as any other intersections experiencing similar level of congestion.
Project Tasks:
Task 1: Document the operational and geometric characteristics at the SH-55/Banks-Lowman Hwy Intersection. This task will also include a short interview with ITD district traffic engineers to identify any other rural intersections experiencing such high levels of congestion [Months 1 and Month 2]
Task 2: Literature review to document the state of the practice in the area of rural intersection congestion mitigation alternatives. [Months 1 and Month 2]
Task 3: Develop a set of alternatives to alleviate the rural congestion at SH-55/Banks-Lowman Hwy Intersection [Months 3 and Month 4]
Task 4: Test the effectiveness of the proposed alternatives in a microscopic simulation environment [Months 3 and Month 4]
Task 5: Develop a white paper to document proposed alternatives and their potential cost and impact [Month 5]
Task 6: Conduct field data collection at SH-55/Banks-Lowman Hwy Intersection during high-travel season, including a typical summer weekend and holiday weekend, to document the magnitude of the problem and verify the validity of some of the proposed measures. [Months 5 and Month 6]
Task 7: Update microscopic simulation analysis and results using field data [Months 6 and Month 7]
Task 8: Project final report [Months 8 and Month 9]
Project Communication Schedule:
Monthly project progress report (ITD 771).
Quarterly project meeting with the project's technical oversight committee.
Needs and Requirements:
SH55 is the only link for the communities between Boise and McCall and the Garden Valley area as well as a heavily used recreational route. Heavy congestion at this intersection creates excessive delays and safety concerns at and upstream from the intersection. Improvements at this intersection will improve safety, mobility, and economic opportunities for these rural communities.
Required Outputs:
- Report outlining existing traffic conditions and roadway geometric constraints including any operational safety challenges.
- Short, medium and long term recommendations for improving intersection operations.
- Basic concept-level roadway plans and cost estimates for intersection modifications in each of the 3 terms noted above.
Implementation:
Depending on the complexity of the proposed solutions, research results/recommendations will either be implemented by ITD maintenance forces or put out to bid for construction by a private contractor.
Expected Outcomes/Savings to ITD:
Currently, the intersection is controlled by flaggers during holiday weekends and it is anticipated that the need exists for similar intersection control during most summer weekends. It is expected that this research project will propose improvements that will eliminate the need for flagger control at the intersection eliminating the man-hour costs for flagging and better intersection operations leading to minimizing delays and motorists’ frustrations, leading to a safer roadway environment. The outcome of the project should eliminate/minimize traffic congestion/delays at the intersection in particular during summer and holiday weekends.