Vizcarrondo-Lebrón, María I.

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    Redesign of a signalized intersection using non-conventional left turn treatments to optimize level of service and delays: Western Plaza case study
    (2016) Vizcarrondo-Lebrón, María I.; Cruzado-Vélez, Ivette; College of Engineering; Valdés Díaz, Didier; Perdomo, José L.; Department of Civil Engineering; Vicente Velez, Nancy Vanessa
    Congestion and safety problems at intersections have been on the rise due to the increased traffic volumes throughout mainline corridors in Puerto Rico, as well as in the United States. As a result, new and innovative intersection designs have baeen developed in order to mitigate these problems. Michigan Lefts include the elimination of direct left turns at intersections by removing left turn phases, which in turn will reduce delays and travel times. A congested intersection in the municipality of Mayagüez, Puerto Rico was chosen as the study site in order to determine the benefits of changing it from a traditional intersection to a Michigan Left intersection. Traffic volume counts were collected at the study intersection as well as at the upstream and downstream intersections. A simulation model was developed in order to compare the delays across the study scenarios. The different scenarios studied included: the existing intersection geometry, Michigan Left applied to the mainline, Michigan Left applied to the side street, and Michigan Left applied to both the mainline and side street. Because the intersection currently has six approaches, it needs various phases in order to adequately service all the vehicles. The study intersection continued to operate under failing levels of service across all scenarios because of the need of numerous phases. Hence, a new model was developed that would essentially incorporate the Michigan Left principles by completely eliminating eastbound and westbound through movements. The new model separated the mainline roadway and the service road that runs parallel to the east, thus reducing signal phases from 7 to 4 at each intersection. In the last scenario, delays were greatly reduced, all approaches operated under acceptable levels of service during both peak hours, and queues were significantly reduced. Numerous signal phases at signalized intersections may cause substantial delays and queues along the roadways, especially along arterials with heavy volumes. Hence, congested intersections may be studied in order to determine if a non-traditional intersection design would improve capacity and overall intersection operation.