Managed lane strategies are “the evolution of traditional lane management strategies, with the primary difference being the idea of active management over the life of the facility”. Kuhn et al. (2005) identified the following as the different types of managed-lanes operational strategies: High Occupancy Vehicle (HOV) lanes, High Occupancy /Toll (HOT) lanes, exclusive lanes, mixed-flow separation/bypass lanes, lane restrictions, and dual facilities. HOV lanes are reserved for vehicles with a driver and one or more passengers. In some cases, other vehicles such as motorcycles, transit buses, and emergency vehicles are permitted in the HOV lanes. When single occupancy vehicles (SOVs) are permitted to use the HOV lanes with a toll, the facilities are known as high-occupancy toll (HOT) lanes. Since their inception in late 1960s, HOV lanes have been increasingly implemented across the United States. Several FDOT projects using managed lanes are currently under consideration in various Districts, including SR-826 in Miami, I-4 in Orlando and the Pensacola Bay Bridge. In addition to encouraging carpooling and increasing person throughput, the HOV facilities help alleviate congestion, improve travel time reliability, and benefit air quality. At the same time design elements of HOV/HOT facilities such as orientation (i.e., contra-flow or concurrent flow), lane access type (i.e., continuous or limited), and lateral separation from general purpose lanes (i.e., buffer or barrier) can also impact the safety of the facility. The Highway Safety Manual (HSM) provides the transportation industry with a methodology to predict crashes and quantify the safety benefits of various design features on various highway types excluding freeway facilities. The recently completed NCHRP Project 17-45, “Enhanced Safety Prediction Methodology and Analysis Tool for Freeways and Interchanges” produced a set of safety prediction methods for basic freeway facilities. Neither of these studies address freeway facilities with managed lanes. Given the increase in the number of managed lane facilities and the lack of systematic methods to analyze their safety, this study aims to develop methods to estimate the expected crash frequency of freeway facilities with HOV or HOT lanes. The scope of the research will be limited to urban freeways, where most of such facilities are situated. In consideration of the data availability issues, this study examines only freeway segments and not ramps or interchange areas. Among the design elements, the focus is on the type of separation between the managed and general purpose lanes. Overall, this research provides procedures that will help FDOT consider safety in decisions about planning and designing freeways with HOV or HOT lanes. The rest of this report is organized as follows. Chapter 2 presents a review of literature on the safety of freeways with managed lanes. Chapter 3 presents a detailed overview of the data assembled and the procedures involved. Chapter 4 presents the safety performance functions estimated. Chapter 5 presents an overall summary of this effort and identifies the major conclusions and areas for future work. Along with this report, spreadsheet implementations of the models presented in Chapter 4 are also available. These may be used by analysts to apply the developed equations for crash frequency estimation of freeway segments with HOV or HOT lanes. (Author/publisher)
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