CHAPTER TWO: LITERATURE REVIEW
The literature review serves several purposes: 1) to guide professionals in the implementation of emergency vehicle preemption; 2) to enable the reader to establish a good foundation of relevant knowledge and raise an awareness of most of the issues,pitfalls and the solutions surrounding EVP implementation and operation; 3) to facilitate communication between stakeholders when EVP planning, designing and implementing details are considered; and 4) to provide balanced information to both the traffic engineer and the fire and rescue communities in order to enhance their knowledge about the possible benefits, alternative approaches, and issues concerning EVP. It is often seen that different groups have different perspective on the significance and consequences of EVP. This broader knowledge will encourage better understanding among the communities and their decision makers.
OVERVIEW OF TRAFFIC SIGNAL FUNDAMENTALS
Background ñ What is Emergency Vehicle Preemption?
Emergency vehicle preemption is an operational strategy that facilitates the movement of the emergency vehicle through the traffic signal controlled intersection. This strategy may lead to reduction in EV response times, and improvements in EV safety. EVP interrupts the normal signal plan and results in an immediate green interval being provided for emergency vehicles including fire and rescue. An emergency vehicle preemption system includes a device or devices that allow a traffic control signal to respond uniquely to the approach of a particular type of vehicle or the occurrence of an unusual condition at or near a signalized intersection. Such systems are designed to increase safety and reduce emergency response times. In cases where the signal provides preferential treatment to other vehicles such as buses, the term signal priority is used because of the conditional nature of the preferential treatment.(Johnson, Mirmiran and Thompson, MHSA 2000)
Why do we need Emergency Vehicle Preemption?
Some factors that contribute to the need for EVP are as follows (Johnson, Mirmiran and Thompson, MHSA 2000):
1) EVP is needed where there is significant congestion and queuing at intersection approaches. Generally it has been suggested that the need for EVP is most needed when the LOS is poor and the during the peak hours. High volume/capacity ratios at the intersection suggest congestion. Thus, volume/capacity and the time of the day are the two main factors, which contribute to delays.
2) Number of accidents involving emergency vehicles is a clear indication of need for EVP, but the absence of accidents does not necessarily indicate that EVP should not be considered (Appendix A5 shows the number of emergency related fatalities as generated from Fatality Analysis Reporting System (FARS) WebBased Encyclopedia).
3) Lack of shoulders and auxiliary lanes does not enable the motorists to pull out and provide a clear path to the emergency vehicle. In some instances, motorists may use the right and left turn lanes, when the queue length in these lanes are not very long.
4) High numbers of emergency vehicle runs per day indicates the likelihood of delays and unsafe conditions to emergency vehicles and the need for EVP.
5) The large size of some of the emergency vehicle causes difficulty for the emergency vehicle driver to maneuver. Larger vehicles normally have a low acceleration rate, in which case providing EVP may help.
6) Inadequate sight distance may support the need for EVP, particularly when the emergency vehicle run is on the side street entering a major roadway or arterial.
7) Complex or unusual intersections with severe skewness may make the safe movement of the emergency vehicle difficult. EVP may be definitely useful in such a case (Johnson, Mirmiran and Thompson, MHSA 2000).
Priority vs. Preemption
Priority and Preemption are often used synonymously, when in reality they are different processes as indicated above. Priority and preemption may utilize similar equipment (e.g. optical emitters and detectors) and may appear similar in operation to an observer. Actually, preemption interrupts the normal process for special events including emergency vehicle while signal priority modifies the normal signal operations process to better accommodate vehicles such as buses.Other preemption has been used traditionally where a high degree of preferential treatment is warranted for safety and other performance reasons. When a signal is preempted, there is less consideration for affecting the existing timing plans such that coordination can be maintained between adjacent traffic signals. In signal priority, more concern for coordination and other factors may be considered. (An Introductory Guide to Transit Signal Priority, 2001)
TABLE OF CONTENTS
LIST OF TABLES
LIST OF FIGURES
CHAPTER ONE: INTRODUCTION
1.1 PROBLEM OVERVIEW
1.2 RESEARCH OBJECTIVES
1.3 RESEARCH APPROACH
1.4 THESIS CONTRIBUTIONS
1.5 THESIS ORGANIZATION
CHAPTER TWO: LITERATURE REVIEW
2.2 OVERVIEW OF EMERGENCY VEHICLE PREEMPTION FUNDAMENTALS
2.2.1 Background- What is Emergency Vehicle Preemption?
2.2.2 Why do we need Emergency Vehicle Preemption?
2.2.3 Priority Vs Preemption
2.2.4 Preemption Scheme and Strategies
2.2.5 System Components
2.2.6 How the System Works?
2.3 SYSTEM ARCHITECHTURE
2.3.1 Logical Architecture
2.3.2 Physical Architecture
2.4 PLANNING AND DEPLOYMENT OF EMERGENCY VEHICLE PREEMPTION
2.4.2 Regional Management and Coordination of Emergency Vehicle Preemption Issue
2.4.3 Types of Technology
2.5 EMERGENCY VEHICLE PREEMPTION OPERATION AND MAINTAINENECE ISSUES
2.5.2 Hardware and Software
2.6 ADVANTAGES AND DISADVANTAGES OF EMERGENCY VEHICLE PREEMPTION
2.7 SIMULATION STUDY
2.8 NEXT GENERATION
2.8.1 Monrovia, California Experience
CHAPTER THREE: A CASE STUDY OF SOUTHGATE DRIVE.
3.2 EMERGENCY VEHICLE CHARACTERISTICS
3.2.1 Temporal Distribution of Emergency Calls
3.2.2 Diurnal distribution of emergency call
3.2.3 Types of emergency vehicle responding to emergency call
3.2.4 Size of platoon of emergency vehicle
3.2.5 Types of emergency vehicles
3.2.6 Analysis of log data
3.3 AN ANALYTICAL METHOD TO EVALUATE THE IMPACTS OF EMERGENCY VEHICLE PREEMPTION
3.3.1 Emergency Vehicle Preemption Evaluation
3.3.2 Definition of terms
3.3.3 Scoring Criteria
3.3.4 Conflict Scores
3.3.5 Mixed message score definition
3.3.6 Delay definition
3.4 VIDEO DATA COLLECTION & ANALYSIS
3.4.1 Data collection form
3.4.2 Case I: Concurrent
3.4.3 Case II: Perpendicular
3.4.4 Case III: Parallel Opposite
3.5.3 Number of confused drivers
3.5.4 Queue Length
3.5.5 Recovery Strategy
CHAPTER FOUR: CONCLUSIONS AND RECOMMENDATIONS
4.2 RECOMMENDATIONS FOR FURTHER RESEARCH