Session 5D: Innovative Interchanges and Intersections

Session Description: See descriptions of individual presentations below.

Moderator: Brian Krul, PE, PTOE, TranSystems

  • Reduced Left-Turn Conflict Intersections, David Petrucci, Jr., PE, PTOE, Safety and Design Technical Service Team, United States Department of Transportation(USDOT) — Federal Highway Administration(FHWA) — Resource Center

This presentation highlights the benefits of reducing left-turn conflicts at traditional intersections and pursuing innovative applications of restricted-crossing and median U-turn designs and concepts, in rural, suburban and urban contexts. The Restricted Crossing U-turn (RCUT) and Median U-turn (MUT) are innovative intersection designs that improve safety and operations via the thoughtful relocation of left turning traffic to downstream median openings, or other locations serving u-turning traffic, which helps to reduce the number and complexity of conflicts between motor vehicle traffic, pedestrians, and bicyclists. Throughout the nation, these innovative intersection designs have been found to reduce crashes (especially more severe crash types), lower travel times, facilitate transit and heavy vehicle traffic, and improve operations.

  • Travel Time Reliability and Innovative Design, Smith Siromaskul, PE, P. Eng, Senior Professional Associate, HDR

Travel time reliability is a measure of effectiveness that is being transitioned in as a required criteria when determining the most appropriate improvement for a project. Reliability is closely related to capacity and can be thought of as a measure of sensitivity. The closer to capacity you are, the less reliable a facility will be. Pushback against innovative solutions often comes in the form of driver expectancy regardless of what before and after studies and field data may indicate. Innovative solutions are often thought of as a last resort. “Concept A works, and our drivers are familiar with it. Why should we try something new?” Travel time reliability as an MOE may help make the argument that something new may be the better choice as it may be less sensitive to traffic volumes. Incorporating reliability is not as straightforward as it seems.

A project is underway in Florida to create a protocol for implementing travel time reliability as a performance measure for future projects by incorporating tools and methodologies developed in the SHRP2 LO4 project. While the SHRP2 project laid the foundation, implementing it is requiring creative use of big data, both historical and current, covering everything from weather data and rain intensity automated from video feeds to interpolated speed and density from side fire radar, loop detection, etc. The goal is the creation of a process to use microsimulation to predict the future variability of traffic operations and the reliability of a facility. Implementation of this process will yield more informed decision making and a better argument for implementation of innovative concepts as something other than a last resort.

The first DDI in Pennsylvania opened to traffic in September 2016, becoming the 73rd DDI to open in the United States. With the success of that DDI project, along with the promotion of DDIs and other innovative intersections by The Federal Highway Administration (FHWA) in recent years, PennDOT is exploring many more locations for DDIs and other innovative designs to improve operations and safety at a lower cost than more “conventional” approaches. But with PennDOT being relatively new to innovative geometric design, the Department sought more guidance for locations where these designs are being considered.

This presentation will explore several projects in eastern Pennsylvania that are proposing DDIs at existing interchanges. These projects went through peer reviews to improve the operations and safety aspects of the design for all users. Additionally, any closely spaced intersections adjacent to the DDI were also evaluated and in some cases, various innovative improvements were recommended.

Speaker Bios:

David Petrucci is a safety engineer with the USDOT Federal Highway Administration’s Resource Center, stationed out of the Baltimore, MD regional office. Mr. Petrucci has 16 years of traffic engineering experience in consulting and government while specializing in transportation operations and design, safety studies, traffic analysis, and simulation modeling. He is a member of the FHWA Intersection, Pedestrian, and Bicycle Safety teams, and provides technical assistance to state, local, and tribal governments throughout the United States and its territories. Mr. Petrucci is an active member of the Institute of Transportation Engineers (ITE) and serves as vice chairperson of the ITE Transportation Safety Council. Mr. Petrucci is an NHI certified instructor, licensed professional engineer, and certified professional traffic operations engineer.

Smith Siromaskul is a senior professional associate with HDR’s office in Portland, Oregon with a background in both traffic engineering and roadway design. Smith has worked on diverging diamond interchanges for over nine years from concept development to final design and construction support. He was a member of the committee that developed the Utah DDI design guidelines and was on the project team that performed the evaluation study of the first DDI in the United States. He has worked on DDIs on over 100 sites across the country and has facilitated DDI design and analysis workshops for various agencies. Smith is a national resource within HDR for innovative intersection and interchange design and analysis.

Gil Chlewicki is an internationally recognized expert and leader on DDIs and other innovative intersections and interchanges. Gil introduced the DDI concept to the transportation world in 2003 and has studied, developed, and designed DDIs for nearly 20 years, along with other innovative geometric designs. He has given presentations and workshops, as well as assisted on DDI and other innovative designs in nearly every US state, Canada, Australia, and several European countries. This does not include other assistance that he has provided unknowingly through his website divergingdiamond.com. He has won two national awards for best papers/presentations which were entitled: “Lessons Learned from Six Operational DDIs in the US” and “Improving Pedestrian Operations at Innovative Geometric Designs.” Within the Transportation Research Board, Gil leads the Alternative Intersection Work Group and is Co-Chair of the Intersection Joint Subcommittee which has six parent TRB committees. Gil is the director of Advanced Transportation Solutions, which is based near Baltimore, Maryland. He is a very frequent visitor throughout the Commonwealth of Pennsylvania.

 
 

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The Thomas D. Larson Pennsylvania Transportation Institute is Penn State’s transportation research center. Since its founding in 1968, the Larson Institute has maintained a threefold mission of research, education, and service. The Institute brings together top faculty, world-class facilities and enterprising students from across the University in partnership with public and private stakeholders to address critical transportation-related problems.

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