Abstract Manager

When looking at improving overcapacity intersections, a typical approach involves adding through lanes or turn lanes and then considering grade separated interchange options.  With the growing acceptance of innovative intersection treatments such as restricted crossing u-turns, continuous flow intersections, and a myriad of mix and match combinations of at-grade innovative elements, practitioners have far more options to add capacity without grade separations.  These treatments vary significantly in footprint, capacity, friendliness to active transportation modes, maintainability, and applicability to any given location.  Even with innovative options in hand, there are times when at-grade options simply aren’t enough.

The traditional approach once at-grade options are exhausted is to go to a fully grade separated interchange with at least one of the two intersecting roadways becoming free flow with ramps providing access to and from the intersecting roadway.  These interchanges can create their own problems when neither roadway is a fully access-controlled facility such as merging and weaving issues with adjacent intersections or driveways.  Free-flowing high-volume treatments can also be challenging for active transportation users and often require significant compromises to accommodate transit stops.  Conversion of an at-grade intersection to a traditional interchange, even one with a small footprint, can be cost-prohibitive or overly impactful in a built urban environment.

This presentation will cover partially grade-separated options that involve less structure, smaller footprints, and blend elements from at-grade innovative treatments to create site-specific solutions that do not require creating a freeway “feel” and the subsequent multimodal challenges associated with free-flowing traffic.

One of the case studies that will be covered includes the 2^nd echelon intersection built in the US which grade separates half of the movements at an intersection.  Lessons learned will include alternatives development, traffic analysis, and staging.

The second case study will cover the intersection of John Young Parkway and Pleasant Hill Road in Kissimmee, Florida, an intersection that includes a grade separation of just one through movement and utilizes a blend of at-grade intersection treatments to fix a highly constrained, high-volume intersection that currently creates nearly a half-hour of delay per vehicle today.  The proposed improvement is entering the final design phase and provides the needed capacity while doing so with minimal widening and right-of-way impacts by blending the single-direction grade separation with a displaced left turn and median U-turns.  Lessons learned will cover the thought process behind the development of the concept that can be applied at other locations.