Summary

The implementation of freeway HOV lanes has been a controversial issue since the 1970's with the Santa Monica freeway experience and continues today. While the implementation of freeway HOV lane mileage has grown, the controversy continues, particularly from the public and environmentalists, partly due to incomplete assessments, and, perhaps in some situations, to questionably implemented sites. This applied research project will provide factual evidence of the effectiveness of existing HOV freeway facilities based on field data and will deliver methodologies for predicting the effectiveness of existing and proposed HOV freeway facilities from the perspectives of both freeway performance and air quality.
Research is needed to evaluate freeways having on-freeway HOV lanes in the light of vehicle-travel, person-travel, occupancy distribution, shape and duration of the peak period, congestion patterns, and air quality. This research will examine both the HOV lanes and adjacent mixed-flow lanes of existing systems using quantitative field data and will develop methodologies for evaluating a wide range of current and proposed HOV freeway facilities in terms of an extensive set of criteria that includes air quality. The research will help to determine the most effective use of on-freeway HOV lanes and to identify situations where and when such lanes may not be cost-effective. This research will aid Caltrans in developing improved guidelines for selecting, designing, and operating HOV facilities. It will also provide insights to Caltrans staff as to how existing HOV facilities might be improved. The results of this research will be available to the general public, environmentalists, and policy makers and hopefully prove useful in the decision making process

Methodology

Two major sets of tasks will be undertaken to work toward the objective of this project. One set of tasks will be directed toward quantitative assessment of on-freeway HOV lanes through an extensive field data assembly effort of a significant number of California HOV freeway facilities. The other set of tasks will be directed toward developing methodologies for assessing a wide variety of current and proposed HOV freeway facilities

1. Task 1: Comprehensive Literature Review and Synthesis of Current Knowledge As an important initial step, the research team will review and take advantage of any previous and current related research. This initial effort would also include interviewing experts in the field with particular attention given to selected CALTRANS staff members and members of the TRB's Committee on HOV Systems.
   
   
2. Task 2: Assemble and Analyze Historical and Current Field Data of HOV Facilities An extensive effort will be undertaken to assemble and analyze historical and current freeway performance data on a significant number of California HOV freeway facilities. The freeway performance data would include vehicle-travel, person-travel, occupancy distribution, and congestion both in the HOV lane and the adjacent mixed-flow lane.
   
   
3. Task 3: Assessment and Development of Methodologies for Estimating Air Quality Two methodologies will be developed for estimating air quality consequences of HOV lanes on freeways. One methodology will be based on the use of the FREQ simulation model and will be used to update that model's air quality module. The other methodology will be based on the use of the PeMS database and will be developed off-line.
   
   
4. Task 4: Application of Modified FREQ Model to Evaluate HOV Lanes The modified FREQ model will be applied to two freeway study sections for the purpose of demonstrating and providing an assessment of the effectiveness of HOV lanes and their impact on air quality. One site will represent typical northern California practice (peak-period only, unlimited access operations, and associated cut-off levels) while the other site will represent typical southern California practice (24/7, limited access operating policies, and associated cut-off levels). The assessment will include vehicular-and person-travel in the HOV lane and adjacent mixed-flow lanes as well as air quality consequence.
   
   
5. Task 5: Application of Off-Line Modified PeMS Database to Evaluate HOV Lanes The modified off-line methodology for estimating air quality based on the PeMS database will be applied to the two study sections and evaluated for vehicular- and person-travel for selected time periods of the day as well as air quality consequences.
   
   
6. Task 6: Documentation and Presentation of the Effectiveness of HOV Lanes The final task of the research will be to develop a document that summarizes the effectiveness of HOV lanes in terms of vehicular- and person-travel in the HOV lane(s) and adjacent lanes, and the consequences to air quality. This document will be based on the literature search and synthesis, the analysis of field data, developed air quality modeling, the modified FREQ model demonstration applications, and the off-line modified PeMS demonstration applications. The document will also include executive summaries developed specifically for the general public, environmentalists, and policy makers.