Safety Implications of Managed Lane Cross Sectional Elements
CHAPTER 1: INTRODUCTION
This report is part of a Federal Highway Administration (FHWA) research project entitled "Synthesis of Operational Aspects and Safety Implications of Reduced Cross Sectional Elements (Buffer Width vs. Shoulder Width vs. Lane Width)."
Managed lanes (ML) are designated lanes and roadway facilities located on or adjacent to controlled access urban highways that are actively operated and managed to preserve preferential service over comparable general traffic lanes. Preferential service often implies faster travel speeds and better reliability than would be observed on adjacent general-purpose (GP) lanes that are not subject to the same level of active management. Various geometric strategies are employed to preserve these benefits such as wider lane widths or wider buffer widths with or without pylons.
The objective of this project was to identify managed lane facilities that are currently employed in the United States in order to inventory the array of strategies regarding lane, buffer, and shoulder (inside and outside) widths. Selected strategies were then to be evaluated to determine the impacts of narrowed widths on safety.
The research was conducted in a series of tasks as follows:
- Task A—Project Initiation. The research team met with FHWA staff to discuss the project direction, scope, and work plan.
- Task B—Collect, Review, and Evaluate Available Literature and Practices. The research team reviewed existing literature on freeway and managed lane safety. Geometric information was obtained for a sample of existing managed lanes. This information was used to aid in identifying potential study locations. The team also identified the availability of crash data suitable for the study.
- Task C—High Occupancy Vehicle/Managed Use Lane Pooled Fund Study Panel Discussion to Develop a Short List of Candidate Facilities for Detailed Evaluation. This task involved meeting with the High Occupancy Vehicle (HOV)/Managed Use Lane (MUL) Pooled Fund Study panel to identify a short list of approximately 12 sites that will be evaluated as part of Task E. More than 12 sites were included in the study to expand the potential of finding statistical relationships between cross section width and crashes.
- Task D—Develop Methodology for Evaluation. This task involved the development of an evaluation methodology that was followed in Task E.
- Task E—Evaluation of Safety and Operational Implications of Reduced Cross-Sectional Elements. This task involved the review and analysis of the crash data and site data to identify potential relationships between cross section (lane, shoulder, and buffer) width and crash frequency or severity.
- Task F—Research Report. This task involved the development of this research report to document aspects of the study's activities and findings.
- Task G—Project Meetings and Teleconference. This task included participation in the following project meetings and teleconferences: kick-off meeting/teleconference, teleconferences spaced throughout the project, and HOV/MUL Pooled Fund Study Annual Meeting held April 2015.
This report includes the following chapters: