CE 572 - Intersection Traffic Operations
Spring 2007

Objectives for today:

• Understand traffic controller subsystem

Topics:

• How a phase terminates
• Designing a basic signal controller and timing processes

Assignment:
The purpose of Assignment 9 is to develop the logic for a basic traffic signal controller and to verify that your logic works within signal controller emulator using Visual Basic for Applications.  Assignment 9 is due on Thursday, April 12th.

You will be given a spreadsheet with the shell for the controller emulator.  This shell includes the following components:

• The controller emulator interface
• The start and stop buttons for the emulator, and the code that reacts to these buttons
• Code that reacts to the detectors being activated

When your signal controller emulator is complete, it must meet the following requirements:

• Accepts input for the three system inputs: minimum green, maximum green, and passage time.
• Starts the emulator when the start button is clicked.
• Stops the emulator when the stop button is clicked.
• Displays the correct indications (red, yellow, green) for the NB and WB signal displays.
• Change the detector status to active when the detector buttons ("NB detector" and "WB detector") are clicked.
• Correctly displays Phase 1 and Phase 2 controller status (timers): minimum green timer, maximum green timer, passage time, and detector status.
• Correctly displays "Phase Timer", the duration of the current green interval.

The following tasks are suggested to structure your design for assignment 9:

• List the input variables already assumed in the VB code that you have been given? (ActivePhase, ActivePhaseCall, ConflictingPhaseCall).
• Develop pseudo code for the phase timing process for each direction, including a list of variables and the logic that both times and terminates the phase.
• Develop a list of tasks that initialize variables, set and change display indication color, and that reset variables as needed during various parts of the process; prepare pseudo code that implements these tasks.

Reading assignment: In preparation for class 21, please complete the following reading assignment:

Traffic Signal State Transition Logic Using Enhanced Sensor Information, (precedence diagrams and scheduling concepts), pp 96-112.
Modeling Traffic Signal Operations using Precedence Graphs by Larry Head, Doug Gettman, Tom Urbanik, and Darcy Bullock.

Please be ready to discuss the following study questions at our next class, based on these readings:

1. What is a priority request server and what are its three parts?
2. What is a precedence diagram and its major components?
3. What are the elements of the precedence network model?

Class notes:
Slides
Written notes

Questions on today's class:
None.