Estimating the Impacts of Access Management Techniques: Final Results

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Abstract:

Frawley, W., W. Eisele, and C. Dusza, Research Report FHWA/TX-04/0-4221-2: Estimating the Impacts of Access Management Techniques: Final Results, prepared by the Texas Transportation Institute for the Texas Department of Transportation, Austin, TX, (2004)
This report summarizes the research activities and findings of an investigation into the impacts of access management treatments. The operational impacts of access management techniques were first estimated through field data collection at selected sites in Texas and simulation of traffic performance. The safety benefits of access management treatments were estimated by investigating crash data from select corridors where access management treatments have been installed.
Three case studies were analyzed regarding travel time and delay, and theoretical corridors were used to provide further insight into corridor performance with changes in median type, driveway density, and traffic volume. Key considerations for using micro-simulation (VISSIM) to investigate access management treatments were identified. A variation was noticed in travel time (and relatively small changes in speed were observed) when comparing a corridor with a two-way left-turn lane (TWLTL) with the installation of a raised median along the three case study corridors and three theoretical corridors.
The research found that the number of conflict points was significantly reduced for corridors with access management treatments; with reductions of up to 60 percent for the case studies and up to 75 percent for the theoretical corridors. The reduction in conflict points illustrates the potential safety impacts of access management. The assessment of crash information used in the analysis identified a relationship between increasing access point density and increasing crash rates. The research also identified a reduction in crashes and crash severity when comparing corridors with a TWLTL to those with a raised median.

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