Seminars - ABSTRACT
David A. Stroud, P.E., AICP, Traffic Engineer and Planner, RS&H
Jaimison Sloboden, P.E., Transportation Engineer, RS&H
Title: Justification and Fine Tuning the Design of Managed Lanes Using Microsimulation to Assess Freeway Operations: The I-95 Express Experience in South Florida
Introduction: The Florida Department of Transportation (FDOT), in partnership with local transit authorities, has developed a project to manage congestion and provide travel options in South Florida. The project, called 95 Express, is a combined Bus Rapid Transit (BRT) and Managed Lanes project. To avoid widening the corridor, existing lane and shoulder widths will be slightly reduced so that an additional lane can be provided on Interstate 95 (I-95) in each direction. The two existing High Occupancy Vehicle (HOV) lanes and two new lanes on I-95 will be converted to limited access Managed Lanes. The project begins in Miami-Dade County, Fla., and extends 20 miles to Broward County, Florida.
Issues: The introduction of managed lanes to the inside (left-side) of a freeway system requires drivers to execute complex maneuvers. The impact of these maneuvers on the existing system must be clearly understood and assessed to justify that the addition of the managed lanes do not degrade overall system performance and safety. The left-side managed lanes introduce cross freeway weaving and weaving within the general purpose lanes that impact the operational performance of the general purpose lanes. The impact of these maneuvers depend on three critical design features, the managed lane ingress/egress design, location of the managed lane access points and their proximity to local access interchanges, and congestion that exists on the freeway system.
The Traffic Analysis Toolbox Volume IV: Guidelines for Applying CORSIM Microsimulation Modeling Software was followed to model the freeway system. CORSIM models with and without the managed lanes were developed. The models were compared to evaluate the operational impacts of introducing the managed lanes. Innovative tools and exhibits were used to convey the operational changes and identify impact.
Conclusions: The traffic analysis performed justified the managed lane project and provided information that resulted in design changes to the managed lanes. The primary design change was elimination of an intermediate managed lane access point to avoid a significant operational problem. Other design changes involved modifications at the managed lane terminal points to improve lane continuity and traffic flow. By following this methodology the analysis provided the justification necessary for project approval and construction. The mythology and tools used are applicable to any managed lane project.
[Stroud and Sloboden Bios]
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