OBJECTIVES
The objectives of this project were to develop methods for the performance assessment and capacity analysis of managed lanes and to develop draft material for the post-2010 Highway Capacity Manual (HCM).
BACKGROUND
Managed lanes are becoming more prevalent on freeway facilities and their operational and geometric characteristics vary greatly. While there is no nationally recognized definition of managed lanes, for the purposes of this project, managed lanes are considered to include high-occupancy vehicle (HOV) lanes, high-occupancy/toll (HOT) lanes, and express toll lanes.
The Highway Capacity Manual (HCM) includes methodologies for analyzing freeway facilities but it does not address managed lanes. Some of the reasons that HCM freeway methodologies may not apply to managed lanes are: (1) unique access patterns with general purpose lanes, (2) significant speed differentials between adjacent lanes, and (3) no opportunities for passing on single managed lanes.
A better understanding of the operational characteristics of freeway facilities with managed lanes is needed. Transportation agencies need information on the performance of the managed and general purpose lanes to plan the facility and determine the pricing strategy to manage demand. Including performance assessment and operational analysis of managed lanes in the HCM would greatly enhance its usefulness to engineers, designers, planners, and decision makers.
TASKS
Task 1. Conduct a literature review on the design and operation of managed lanes and summarize information on performance measures and operational analysis methods for managed lanes. Review the latest methods for determining speed-flow-density curves and capacities on freeway segments. Catalog the different types of managed lane designs (e.g., barrier-separated, buffer-separated, non-separated, access point design, typical sections, single lane and multi-lane, reversible).
Task 2. Develop a performance-measurement framework for freeway facilities comprising both managed and general purpose lanes. The framework should include performance measures for the managed and general purpose lanes and consider the use of composite measures for the facility. The performance-measurement framework should provide inputs to toll demand models commonly used for managed lanes and allow transportation agencies to assess the facility’s operation and convey system performance information to the public.
Task 3. Develop a data collection and analysis plan to support Tasks 6 and 7. Data from existing traffic management systems and transit vehicle locator systems on facilities with managed lanes should be used as practical, augmented by original data collection as project resources allow. Data collection sites should include facilities with single and multiple managed lanes and cover the full range of designs for separation between the general purpose and managed lanes. If adequate field data are not available or feasible to collect, validated microscopic simulation models may be used to generate synthetic data if the models are properly calibrated and the results thoroughly documented.
Task 4. Within 4 months of the contract start date, submit an interim report summarizing Tasks 1 through 3. The interim report shall also contain a detailed, updated work plan and an updated budget for the remaining tasks.
Task 5. Carry out the Task 3 data collection plan as approved at the interim meeting.
Task 6. Assess the applicability of the HCM 2010 freeway analysis methodologies to single- and multi-lane managed-lane operations, including the effects of cross-sectional elements. Determine whether these methodologies can be modified to properly model the operation of managed lanes. Discuss the results in a web conference with the panel.
Task 7. Develop methodologies for quantifying the performance measures identified in Task 2 for managed lanes, including their access points and termini. The methodologies should account for the effect of transit and other heavy vehicles on the managed lanes. The methodologies should also account for the effect slower-moving traffic in an adjacent general purpose lane has on uncongested managed-lane traffic for different types of separation. The methodologies should include speed-flow-density curves based on field data and recommend maximum service flows, recognizing that managed lanes are intended to operate uncongested. Describe limitations of the methodologies and situations where alternative analysis tools should be used.
Task 8. Develop a computational engine for the Task 7 methodologies, based on HCM 2010 requirements and building upon HCM 2010 modules as applicable. The computational engine should follow the documentation requirements for the HCM 2010.
Task 9. Prepare draft text for the HCM, either as part of the Freeway Facilities chapter or as a separate chapter.
Task 10. Submit a final report that documents the entire research effort and includes the Task 9 text as an appendix.
