Gilbert Chlewicki, P.E., Division Director at ATS/American is the “father of the DDI” and is considered the national expert on the DDI. As you will read in the history section, Chlewicki came up with the idea of the DDI back in 2000 and wrote a term paper on the idea. The name “diverging diamond interchange” was his creation. Six months after developing the design, he was on vacation in France when he surprisingly went through a “diverging diamond” on his tour bus to Versailles. Chlewicki came back home determined more than ever that this was a great concept worth studying and reporting. He then wrote and presented the ground-breaking paper on the DDI at a Transportation Research Board (TRB) sponsored conference in 2003.

Chlewicki has a dozen (12) years of experience in regards to the DDI, examining every issue such as geometric design, signal placements, traffic design, driver acceptability, pedestrian and bicycle issues, and locations for implementation. Chlewicki was the primary designer of the first DDI that was proposed in Maryland that ultimately was not selected as the preferred alternative due to the low traffic volumes that made any alternative viable.  He has also written a new paper on the DDI related to the signal and crossover design that was presented at the 2010 annual TRB meeting.  He also presented a paper in the summer of 2010 at the ITE annual meeting that examines variations of the DDI.  His 2011 paper that was published in Transportation Research Record shows why the DDI should be initially investigated for all interchange improvements.  He has several other papers on the DDI that have yet to be submitted for publication, but hopes to get them out in the near future. Chlewicki has now given presentations on the interchange in over a dozen different states/provinces in various formats to various audiences (DOTs, TRB, ITE, general public).

Chlewicki went to the ribbon cutting ceremony for the first DDI in the United States in Springfield, Missouri. While there he spent a lot of time with the project manager discussing all the aspects of the interchange. Chlewicki evaluated the design and observed firsthand how traffic behaved within the new interchange.

Chlewicki has expertise in other alternative intersection and interchange designs. He has several new geometric designs that will be introduced over the next several years and has great knowledge on the new designs that are currently out there.  But Chlewicki is a jack of all trades when it comes to transportation. He has experience in transportation planning, traffic design and geometric (final roadway) design. He has expertise on maintenance of traffic issues. He has worked on projects in all of its stages which include planning, design, design-build, and even construction inspection. He has significant knowledge on diverse subjects such as traffic calming and transportation demand management.  He has even done some transit planning.  He finds transportation solutions that work, which often saves money at the same time. 

Mr. Chlewicki is the director of Advanced Transportation Solutions, a division of American Consulting that specializes in solving difficult transportation issues to improve safety, reduce congestion, and find cost efficient solutions through best practices and innovation. Chlewicki is also a member of the Operational Effects of Geometrics Committee at TRB and the Management & Operations/ITS Council at ITE. He is leading a new working group at TRB on Alternative Intersections. His involvement at TRB and ITE is an outward example of how he wants to advance the transportation profession as well as improve transportation issues to better the world we live in.

Please feel free to contact Chlewicki at for information, a presentation, and/or assistance on the diverging diamond interchange or any of your transportation needs.

Publications on the DDI by Chlewicki:

  1. Chlewicki, G., New Interchange and Intersection Designs: The Synchronized Split-Phasing Intersection and the Diverging Diamond Interchange. Presented at 2nd Urban Street Symposium, Anaheim, California, 2003 and Published on Compilation CD.
  2. Chlewicki, G., Operational Effects of the Diverging Diamond Interchange. 89th Transportation Research Board Annual Meeting DVD, Washington, D.C., 2010.
  3. Chlewicki G., Variations of the Diverging Diamond Interchange. Presented and Published at the 2010 ITE Annual Meeting, Vancouver, British Columbia, August, 2010.
  4. Chlewicki G., Should the Diverging Diamond Interchange Always Be Considered. Transportation Research Record Volume 2223, p.88, Washington, D.C., 2011