CE 572 - Intersection Traffic Operations
Spring 2007

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The Course Materials page includes information on the schedule for class topics, assignments, and examinations.

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What is Intersection Traffic Operations
There are three basic types of intersections, each defined by the type of control that is used: (1) signal controlled, (2) stop or yield sign controlled, and (3) uncontrolled.  Each intersection type is most appropriately used for a given set of traffic volume and intersection geometry conditions.  During this class, we will study the first type, intersections that are controlled by traffic signals.

There are nearly 300,000 signalized intersections in the United States today.  While a recent national report card gave many traffic signal systems poor grades, there are a number of expert engineers and technicians who understand how to efficiently time the signals for which they are responsible.   But there are too many who have not been adequately trained or who don’t understand the basics of signal timing and operations.  Further, our nation’s universities are not doing their part in providing the education and training on traffic signal systems. 

This deficit is understandable in part when you look at the resources that are currently available that document how signal systems operate and the good practices that ensure efficient operations and good service quality for users of the system.  Many states and local jurisdictions do have standards that guide their signal timing design and practices.  However, many of these standards are based on experience and not on good theory or science.  Other books or articles touch on parts of signal systems.  But none provide the kind of broad perspective and specific details on traffic signal operation.  This book/course is an attempt to fill at least a part of this gap.

We have established two objectives in preparing this material.  First, it is important to understand the traffic control system and its four components, how they work together, and how each of these components functions individually.  Second, it is important to be able to design the components of the system to be able to operate in a defined/specific environment.

What is the traffic control system?  For isolated traffic control systems, the system is composed of four components or subsystems:  the users of the system, the detection or sensor subsystem, the control subsystem, and the display subsystem.  These components work together in pairs, in a linear fashion.  Each is connected directly with two of the other subsystems, dependent on or responsive to one and directly influencing the other. 

• The detection subsystem detects (responds to the presence of) the users:  A user approaches the intersection and is detected by the detection system.
• The control subsystem responds to the input provided by the detection system: the detection system places an active call to the control system.
• The display subsystem responds to the status of the control subsystem: The control system, based on its current state, sends information to the display system.
• Users respond to the display subsystem.

This Course
This course will focus on the operation of the signalized intersection, really the system that we call the traffic signal control system.  We will focus our work on the isolated intersection, or one that is not connected to other intersections.  During this semester you will learn about four subsystems described above and how they interact.

I have established two fundamental learning objectives for you during this semester:

• You will understand the traffic signal control system, its four subsystems, and how each subsystem relates to each of the other subsystems.
• You will be able to design the components of the system and its four subsystems for a specific set of conditions (traffic flow and geometric conditions).

Within these two learning objectives, I have identified a set of skills and abilities that I hope that you will have by the end of this semester. These skills and abilities, phrased in terms of learning objectives, are listed below:

The Traffic Signal Control System and Its Subsystems
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Applications of the System to Problems
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Closing Thoughts
I will make every effort to make this course both challenging and enjoyable.  I will try to create experiences that invite you to learn new things and to apply what you learn to real situations. I hope that you enjoy the material that we will cover during this semester and it helps to broaden your skills and experiences in transportation.  I look forward to working with each of you.