Print this page Intersection Geometric Design
Gregory J. Taylor, P.E.
Course Outline
This four-hour course summarizes and highlights the geometric design process for modern roadway intersections.
The main objective of intersection design is to facilitate the roadway user and enhance efficient vehicle movement. The course will give engineers and designers an in-depth look at the principles to be considered when selecting and designing for intersections. Topics covered include: human factors; traffic considerations; physical elements; and economic factors.
This course includes a multiple-choice quiz at the end, which is designed to enhance the understanding of the course materials.
Learning Objective
At the conclusion of this course, the participant will understand:
- General intersection design considerations – function, objectives, capacity;
- Alignment and profile;
- Sight distance – sight triangles, skew;
- Turning roadways – channelization, islands, superelevation;
- Auxiliary lanes;
- Median openings – control radii, lengths, skew;
- Left turns and U-turns;
- Roundabouts;
- Miscellaneous considerations – pedestrians, traffic control, frontage roads; and
- Railroad crossings – alignments, sight distance.
Intended Audience
This course is intended for civil engineers and contractors.
Benefit for Attendee
Attendees of this course will be given an in-depth look at design principles to be considered for at-grade roadway intersections.
Course Introduction
Intersections are unique roadway elements where conflicting vehicle streams (and sometimes non-motorized users) share the same space. There are clearly many considerations, including costs, maintenance, adjacent land uses, operational and safety impacts, environmental impacts, and infrastructure needs. The designer’s task requires balancing trade-offs in order to provide safe, efficient, and cost-effective transportation of people and goods. This course will show the participant how to use A Policy on Geometric Design of Highways and Streets (“Green Book”) – Chapter 9 to plan and design effective intersections.
Course Content
The course content is contained in the following PDF file:
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Course Summary
This course summarized and highlighted the basic elements of at-grade intersection design. There are clearly many considerations, including costs, maintenance, adjacent land uses, operational and safety impacts, environmental impacts, and infrastructure needs. The designer’s task requires balancing trade-offs in order to provide safe, efficient, and cost-effective transportation of people and goods.
Intersections are similar to other major infrastructure projects by consuming valuable resources and often adversely affecting the users or those in close proximity to them. All parties charged with resource protection normally expect any adverse effects to be addressed in the planning and design of highways.
The mere application of design standards and criteria to ‘solve’ a problem is inadequate. The various complex safety and operational relationships behind the design guidelines and criteria must be clearly understood. Designers must be prepared to present the reasons for a design, and be prepared to develop any alternatives. This is possible only if the designer understands how all elements of the roadway (horizontal and vertical alignment, cross section, intersections, and interchanges) contribute to its safety and operation.
The contents of this course were intended to serve as guidance and not as an absolute rule. It was written to help you learn to use the AASHTO “Green Book” more effectively for designing at-grade roadway intersections.
Related Links and References
The following reference books were used by the author in the preparation of this course:
American Association of State Highway and Transportation Officials www.transportation.com
Quiz
Once you finish studying the above course content, you need to take a quiz to obtain the PDH credits.
DISCLAIMER: The materials contained in the online course are not intended as a representation or warranty on the part of PDH Center or any other person/organization named herein. The materials are for general information only. They are not a substitute for competent professional advice. Application of this information to a specific project should be reviewed by a registered architect and/or professional engineer/surveyor. Anyone making use of the information set forth herein does so at their own risk and assumes any and all resulting liability arising therefrom.
