The National Academies

NCHRP 03-55(4) [Final]

Performance Measures and Levels of Service in the Year 2000 Highway Capacity Manual

  Project Data
Funds: $159,250
Research Agency: JHK & Associates/TransCore
Principal Investigator: Adolf D. May
Effective Date: 1/8/1996
Completion Date: 10/31/1997

The Transportation Research Board (TRB) Committee on Highway Capacity and Quality of Service (HCQS) intended to publish a new version of the Highway Capacity Manual by the year 2000 (HCM 2000). There was a critical need to enhance the system of performance measures, measures of effectiveness (MOEs), and levels of service (LOSs) to be provided in the new version of the Manual.

The objective of this research was to recommend appropriate MOEs and additional performance measures, methods for estimating them, and LOS structures for use in the HCM 2000. All recommendations considered the special nature of oversaturated conditions and consistency of performance measures to allow facility comparison and aggregation across systems.

The final report was received and approved by the panel. It will not be published but was distributed to the TRB HCQS Committee for their use in developing the Year 2000 Highway Capacity Manual.

The research consisted of the following tasks: (1) For each facility type included in the current HCM, identify, evaluate, and recommend performance measures. Definitions of performance measures must be consistent among different facility types. At least one of the recommended performance measures shall be a time-dimension-related measure. Some of the performance measures should allow route, network, or other combined facility performance assessment. Discussion of the performance measures should include the statistical considerations in collecting performance-measure data in the field. As many performance measures as practical should be recommended to provide additional information about traffic operations and to provide useful data for broader evaluations, such as environmental, economic, or safety analyses, and demand forecasting. (2) For each performance measure recommended, identify, evaluate, and recommend methods that can be used to estimate them, in undersaturated and oversaturated conditions. If applicable, the analysis period should be included as an input to the method. Discussion of the methods should include the reliability of the estimated measures. (3) Recommend one MOE for each facility type with appropriate thresholds for use in determining LOS A to E. The MOE must be related to the facility user's perception of the facility's quality of service. (4) For each facility type included in the current HCM, recommend a structure for LOS F that will better express to technical and nontechnical people the impact of oversaturation on the traveler. LOS F for the HCM 2000 is defined to occur when either the MOE (preferably, the one used for LOS A to E) exceeds some predefined threshold or when demand exceeds capacity. The recommended structure might include some measure of the duration and extent of the oversaturation. (5) Submit an interim report documenting the results of Tasks 1 through 4 and assist in conducting a joint workshop on the interim report for the NCHRP Panel and the TRB HCQS Committee in conjunction with the 1996 Mid-Year Meeting of the TRB HCQS Committee. Revise the report recommendations based on the results of the workshop. (6) Develop several case studies that demonstrate how the recommended performance measures can be used in typical analyses. The case studies must include multifacility and intermodal types of system analyses as well as key facility types. The case studies may be hypothetical or based on actual field data and situations. The case studies should be suitable for inclusion in the HCM 2000 as example problems. (7) Submit a draft final report documenting the entire research effort. In addition to the revised recommendations and the case studies, the report must include recommendations on needed research on methods of estimating performance measures. (8) Conduct additional research to determine how oversaturated conditions should be handled in the HCM 2000. Finalize these recommendations after presenting them to the panel and TRB HCQS Committee at their 1997 summer meeting.

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