Ingenuity Magazine Summer 2020

Pond Ingenuity Summer 2020 5 These new challenges require the examination of alternative intersection treatments. Pond has partnered with several local counties to employ these alternative intersection solutions and maximize existing infrastructure. Critical Roadway Planning Fayette County, Georgia was experiencing strong growth and increased congestion with the high volume of commuters along State Route 74. What once was a rural and underdeveloped corridor now carried over 36,000 vehicles daily. Proximity to the airport and residential development drives the increased traffic demand in this area – demand that the infrastructure was not equipped to efficiently support. By leveraging community and stakeholder input, the data revealed that access management, accessibility and mobility were primary concerns of commuters. They also requested that the 4-lane road be maintained, rather than further widening the corridor. When conducting the Fayette County’s SR 74 Comprehensive Corridor study, the team performed a thorough analysis that would establish a unified vision for the corridor, understand the long- term transportation needs, address the congestion and future growth needs, and provide capacity to maintain corridor mobility. Alternative Intersection Solutions These new challenges require the examination of alternative intersection treatments. The traditional solution of widening these corridors is increasingly difficult in urban areas due to the physical constraints of development, environmental and social considerations, and fiscal constraints. Alternative methods provide new opportunities to emphasize safety, reduce delay, control critical queues, enhance signal coordination, and improve pedestrian crossings. The most cost effective and least disruptive way to address congestion is by increasing efficiency and safety at the intersections, which are the constraint points of the corridor. Intersection improvements have been relevant since the existence of roads. As cities continue to evolve and navigate future growth, there is an increasing need to refine processes and improve traditional methods that emphasize efficiency. Implementing methods such as restricted crossing U-turns (RCUTS), median U-turns (MUTs), continuous flow intersections (CFI) center turn overpasses and two- level signalized intersections function to reduce the number of separate movements. This reconfiguration allows critical flows to occur simultaneously. Utilizing these treatments prove to be effective on intersections with high volume to capacity ratios and heavy travel volumes. Evaluating Intersection Options Understanding the benefits and limitations of each intersection innovation is important for evaluating which solution is the most suitable for a specific corridor. Each solution considers the movements that require the most “green time” and minimize the activity to increase efficiency. The first option is a restricted crossing u-turn. This kind of intersection reduces the critical movements where through volumes crossing the corridor are lighter. A median u-turn reduces critical movements where through volumes are heavier, such as a major crossroad. Alternatively, a continuous flow intersection (CFI), or a displaced left turn (DLT), eliminates left turns from the main intersection by crossing them over sooner. This results in a minimal number of movements for crossing arterials and manages high volumes with fewer potential conflict points. Another option is a center turn overpass, which removes left turns from the main intersection by elevating them to a separate intersection above or below grade. This overpass serves a similar function as a CFI but reduces critical movements vertically instead of horizontally. Finally, the lesser-known two-level signalized intersection reduces the critical movements to a two-phase intersection with through movements instead of left turns. While some of these methods have been applied widely across the US, others have yet to be installed. As agencies begin to adopt these alternative modes, planners will understand what treatments are the most effective for each specialized corridor. The team proposed the Restricted Crossing U-turn technique (RCUT), which is useful for accommodating large volumes of vehicles and serving as a safety countermeasure for unsignalized intersections. They also recommended implementing a Median U-Turn (Michigan Left) to allow for left-turns via one-way U-Turn crossovers in a wide median. The main and crossover signals are coordinated to allow vehicles to turn right to go left. The road would account for pedestrians by protecting them from left turn conflicts in the large median refuge area. Based on the results of the conducted study, a SuperStreet was recommended in Tyrone and Peachtree City. By implementing 8 signalized RCUTs, 7 unsignalized RCUTs, 1 median left turn, 1 displaced left turn and 1 continuous green turn, the improvements enhanced safety by an estimated 20 percent. The SuperStreet was able to increase efficiency during peak traffic hours, all while meeting the community’s expectations by retaining the 4-lane road. Meeting the mobility needs of an increasing population calls for innovative solutions. As communities prepare for higher volumes on congested corridors, it is beneficial to consider the significant operation and safety advantages of alternative intersections. These methods can address increasing delays and risk exposure more effectively than conventional methods. With the use of the Intersection Control Evaluation (ICE) process as an evaluation framework, transportation professionals can examine traffic patterns and reduce the amount of movements drivers must make to cross the corridor. As these alternative methods become more common, they have the potential to improve the commutes of millions of drivers and pedestrians by reducing delay and making the roads a safer place to be.  Richard Fangmann, PE, PTOE VP of Transportation Planning