Submitted by Sabra, Wang & Associates



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December 30, 2003

Table of Contents


December 30, 2003 1

Table of Contents 2

1 Introduction 3

1.1 Purpose 3

1.2 Signal Timing Overview 3

1.3 Report Outline 4

2 Existing Signal Timing Process 6

2.1 Trigger Event 6

2.2 Field Adjustments 6

2.3 System Retiming 8

3 Host Hardware Environment 20

3.1 Traffic Signal Controller Development 20

3.2 Basic Timing Parameters 22

3.3 Coordination Timing Parameters 23

3.4 NTCIP 24

3.5 Universal Traffic Data Format 25

3.6 Hardware Environment Summary 26

4 Literature Review 28

4.1 Signal Timing Process 28

4.2 Signal Timing Optimization 29

4.3 Field Deployment 30

4.4 Performance Evaluation 33

4.5 Data Management 34

4.6 Documentation 37

5 Future Research 38

5.1 Data Collection 38

5.2 Data Management 41

5.3 Data Structure 47

5.4 Intersection Performance Evaluation 49

6 Conclusions 52

6.1 Extended Signal Timing Manual (Project 8) 52

6.2 Short Count Procedures (Project 1) 52



6.3 Estimate Turning Movements from Detectors (Project 3) 53



1 Introduction


Establishing, implementing, and maintaining optimally timed traffic signals is not a simple task. Even when the process is applied to a single, isolated controller, the path to optimum signal timing is paved with problems. One area of the process has been the focus of much academic research over the years, signal timing optimization. As a result, the practicing Traffic Engineer has many optimization models to choose from when retiming traffic signal. Transyt-7F, Passer II, and Synchro are examples of these models. The advent of the Closed Loop System (CLS) and all modern, area-wide traffic signal systems provide the capability of downloading traffic controller timing parameters which has helped problems associated with deployment of new signal settings. Other areas have had less success; data collection and data management are two areas that exhibit opportunities for improvements to the process.
This report considers the entire signal timing process, defines specific areas where progress has been made, identifies the interfaces between these areas, and identifies specific areas where additional research may be expected to improve the signal timing process. This background provides the basis for the identification of specific areas for improvement. Specifically, this report identifies five distinct procedures (Optimization, Deployment, Evaluation, Data Management, and Documentation) associated with the signal timing process. Each of these procedures is examined and evaluated. As important as each of the five procedures is to the process, the interface between each of these procedures is at least equally important and likely provide fruitful opportunities to improve the overall Signal Timing Process.

1.1 Purpose


The purpose of this report is to identify the steps that are required to time traffic signals, and to identify areas that will result in improved traffic signal timing. These steps define a continuing process that may be manual, semi-automated, or fully automated. In the abstract, the process is as applicable to a single isolated controller as it is to a fully integrates city-wide traffic signal system. The process itself can be defined as a series of procedures (steps). This report defines these procedures, identifies the inputs and outputs used by each procedure, examines the boundaries between each procedure, and identifies opportunities for improvements in the process.

1.2 Signal Timing Overview


It is useful to consider the Signal Timing as a process that uses four distinct procedures and one interrelated procedure: Data Management, Signal Timing Optimization, Field Deployment, and Performance Evaluation are the four quadrant procedures of the Signal Timing process. Documentation is the common element that encompasses the other four procedures. This concept is shown graphically on Figure 1.
The four quadrants are depicted simplistically as independent bubbles in Figure 1. Each quadrant receives data from one bubble and sends data to another bubble. The center bubble, Documentation, is central to the process and serves as the repository of information regarding the process.
This structure is used to provide a framework for this analysis. We are able to focus on specific elements of the process without losing the overall perspective. Our emphasis is on not only the four quadrants, but also on the interface between them. In fact, the boundaries between the quadrants are areas that are likely to provide the most potential benefit.



Figure 1. Signal Timing Process.



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