Introducing a whole set of courses dedicated to learning about the diverging diamond interchange.  These courses have been given in the past to audiences of students, public agency officials, and consultants.  Now they are available to everyone.  To schedule a course in your area or to get more information on availability, please contact us at  Please see our other courses on other transportation topics here.

DDI 100 Series - General knowledge of the DDI and innovative geometrics

DDI 200 Series - Details within the DDI

DDI 300 Series - Expanding the DDI Concept

DDI 400 Series - DDI Seminar

(Note:  Courses are designed to be an hour long, except for the 400 series.  However, length of courses can be adjusted when needed.)

DDI 101 - Why transportation agencies are converging to the diverging diamond interchange

This is our introductory course and most popular.  In this course, you will learn the history of the DDI, how the DDI works, what are the benefits and limitations of the design, and how some of the concerns of the design are addressed.  By the end of this course, you will understand why engineers who understand the basic elements of the DDI are so excited about this design.

DDI 102 - When should I consider the DDI

Prerequisite:  DDI 101 or equivalent - The DDI works best when there is at least one heavy left turn movement and/or unbalanced thru movements.  Does that mean you shouldn't consider the DDI in other scenarios?  This course will explore when you know for sure that the DDI won't work and when you should consider it and why.  The answers may surprise you.

DDI 112 - Combination of DDI 101 and DDI 102

DDI 150 - Introduction to Innovative Geometrics

This course will explore the world of innovative geometrics.  You will learn what innovative geometrics are, what the benefits of innovative geometrics are, and why there aren't more innovative geometric designs currently in the field.  You will also get an introduction into many of the innovative intersections, interchanges, and corridor designs that currently exist.

DDI 151 - Ways to defeat the curse of the dreaded left turn (or British right turn)

Designing roads would be so much simpler if there was no worry about the dreaded left turn. One of the main goals of innovative geometry is to address different ways to deal with left turns that were not considered in the past.  This course will go into several options that address how we can handle left turns to make our systems operate more efficiently and safer.

DDI 152 - Reconsidering Left-Side Ramps on our Freeways

Left side on and off ramps are generally discouraged on fully controlled highways due to reasons such as driver expectation and safety concerns.  This course will take a closer look at whether the reasoning behind discouraging left side ramps is justified as well as look at some of the major advantages of left-side ramps that are not usually considered.

DDI 199 - Custom introductory course on the DDI or any other innovative geometric design

DDI 201 - Operational effects of the DDI

Prerequisite: DDI 101 or equivalent - This course will go into detail on the traffic operations both inside and outside of the DDI.  You will learn the different traffic flow theories of the DDI, how to optimize the traffic operations, and how the geometry of the DDI plays a part in the traffic operations.

DDI 202 - Geometric considerations of the DDI

Prerequisite: DDI 101 or equivalent - So you feel that the DDI could be the right solution, but you are worried about all the unique geometrics involved.  This is the right course for you.  You will learn many of the little details involved with designing the interchange including some critical details that would seem at first to help in the design but might actually make the design worse.

DDI 203 - Handling all modes of transportation within the DDI

Prerequisite: DDI 101 or equivalent - Cars are not the only vehicles that go through the DDI.  In this course you will learn how the DDI can handle trucks, bicycles, pedestrians of all types, and more.  You will learn the different options available to handle the different modes and the advantages and disadvantages of each option.

DDI 204 - Disagreements in the field

Prerequisite: DDI 101 or equivalent - Like any new design, there are disagreements about how to handle certain features of the DDI.  This course will take an objective look into what are some of the disagreements and what are the arguments for each opinion.  Then there will be a discussion of which opinions make sense as it relates to various situations.

DDI 205 - Safety features of the DDI

Some people find it hard to believe that the DDI is a safe design but it is.  With this course you will find out why the DDI is safer than other diamond interchange forms, some of the safety features of the design, and some of the details that are important in the design to ensure the safest DDI possible.

DDI 299 - Custom course on a specific topic related to the DDI

DDI 301 - Mutations of the DDI

Prerequisite: DDI 101 or equivalent - As great as the DDI can be, there are still limitations to the use of the design.  This course introduces new designs that combines other geometric concepts with elements of the DDI to form new designs that have other unique benefits.  The course will discuss the following designs: the diverging double roundabout interchange, expanded diverging diamond interchange, diverging windmill interchange, diverging partial cloverleaf interchange, and the synchronized split-phasing intersection.

DDI 311 - Diverging Double Roundabout Interchange

Prerequisite: DDI 301 or equivalent - The diverging double roundabout interchange (DDR) can be a nice alternative to the DDI when there are a couple of small issues preventing the DDI from being an option.  In this course you will learn how the design works, the benefits of this design, and some of the geometric and traffic consideration that are needed to build the best DDR.

DDI 312 - Expanded Diverging Diamond Interchange

Prerequisite: DDI 301 or equivalent - This design looks specifically into the issue of how to incorporate the DDI design with service roads or an intersection that is too close to the potential DDI.  This course will discuss the synchronization of the signals needed to make the expanded DDI work and a multitude of possible way to design the expanded DDI. 

DDI 313 - Diverging Windmill Interchange

Prerequisite: DDI 301 or equivalent - The diverging windmill interchange can be an excellent option when there are tight right of way constraints.  The design avoids weaving issues and can be a very cost effective option with the potential for no signalized intersections.  This course will teach how this design operates, what are the benefits and limitations, and some of the potential design features.

DDI 314 - Diverging Partial Cloverleaf Interchange

Prerequisite: DDI 301 or equivalent - This is another unique design that can potentially be built without any signalized intersections.  Learn the details about the diverging partial cloverleaf including how it works, its benefits and limitations, and the different variations of the design. 

DDI 315 - Synchronized Split-Phasing Intersection

The synchronized split-phasing intersection is the at-grade cousin of the DDI and was introduced at the same time as the DDI in 2003.  This design has been overshadowed even though it has many potential benefits in operations and safety.  This course will discuss the operations, benefits, limitations, and potential applications of this great design. 

DDI 400 - Day long seminar on the DDI

DDI 400 combines the material covered in DDI 112, DDI 201, DDI 202, DDI 203, DDI 204, DDI 205, and DDI 301 in a day long seminar.

DDI 410 - Half day seminar on mutations of the DDI

Prerequisite DDI 101 or equivalent - This course will combine the material in DDI 311, DDI 312, DDI 313, DDI 314, and DDI 315.

DDI 450 - Seminar on innovative geometric design

This seminar can be custom made in length and material on the various innovative geometric designs that are out there and go into some detail for each of these designs.