In the United States, an average of one-quarter of traffic fatalities and roughly half of all traffic injuries occur at intersections. The Federal Highway Administration (FHWA) describes intersections as “planned points of conflict in any roadway system” where vehicles, pedestrians and bicyclists cross, separate or join paths ( These planned, and sometimes unplanned, interactions make intersections a high priority in addressing roadway safety to reduce injuries and fatalities.

A number of conventional approaches can be taken to improve intersection safety, from traffic control devices such as signs, markings, and signals, to geometric designs such as roundabouts. Yet many arterials and interchanges remain terribly congested, and conventional measures often provide little relief. Unconventional designs, such as superstreets, median u-turns, and diverging diamond interchanges, are strong alternatives to improving those congested corridors and intersections.

Join instructor Joe Hummer to discuss the best of the unconventional intersection and interchange options.  Joe is a foremost authority on unconventional intersection and interchange design, having invented several designs and worked closely with the FHWA as lead investigator on a number of reports and research projects. He will guide the class in an exploration of the history, planning, design, and operation of the major designs including continuous flow, quadrant roadway, and grade-separated intersections.  By the end of the class, students will understand which design has a realistic chance to help in a particular spot.

“Unconventional intersections are not a blanket replacement for conventional intersections,” Hummer explained. “Good planners and engineers make informed decisions about the best design for a specific location taking into account the capabilities of different types of intersections to address specific issues. Research shows that, when placed in an appropriate location, unconventional intersections are safe, reduce travel time, and increase traffic capacity, helping to reduce congestion down the road.”

The workshop should be of interest to any planners, designers, and operations professionals who work on intersections and interchanges.  No prior knowledge of intersection or interchange design or operations is needed.  Only basic math skills are needed to follow the examples used in the workshop.  The workshop should be helpful to DOT, city, and county staff members as well as to consultants.

This hybrid online class will combine both live instruction and independent online work that you will complete during the day.  Independent work will include quizzes, readings, videos and short assignments.  Access to a computer with a webcam (either a camera that is built into your laptop or one that connects via USB), a reliable internet connection and a workspace that is free from distraction and noise will set you up for success.

For additional information on unconventional intersections, you can find FHWA informational guides at Guidebooks are available for:

  • Diverging diamond interchanges
  • Displaced left turn intersections
  • Median U-turn intersections
  • Restricted crossing U-turn intersections (primary author: Joe Hummer)

To register go to:

About the Instructor
The class and laboratory instructor, Joseph E. Hummer, PhD, PE, is the state traffic management engineer in the mobility and safety division of the NCDOT.  Joe began researching unconventional designs in 1990, has published numerous articles about them, and has invented several new intersection and interchange designs.  His two-part series in the ITE Journal in 1998 helped spark interest in the area.  More recently, he was a co-author of the FHWA informational report on six of the most promising designs, he was the principal investigator of the FHWA research project investigating the effects of diverging diamond interchanges, and he was the primary author of the FHWA guidebook on superstreets.  Joe was a professor at North Carolina State University and was chair of the department of civil and environmental engineering at Wayne State University before joining NCDOT in May 2016.  Since joining NCDOT he has contributed to over 50 Transportation Improvement Projects.

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