Polytechnic Institute of New York University
Elena S. Prassas, Ph.D.
William R. McShane, Ph.D., P.E., P.T.O.E. President, KLD Engineering, PC.
Professor Emeritus Polytechnic Institute of New York University
PEARSON
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Library of Congress Cataloging-in-Publication Data
Roess, Roger P. Traffic engineering / Roger P. Roess, Elena S. Prassas, William R. McShane. - 4th ed.
p. cm.
HE355.M43 20H
Profession 1
Function 3
United States 8
Engineering 12 1
Engineer 13 Standard References for the Traffic
Engineer 14 Metric versus U.S. Units 15
Closing Comments 15
3 .1 Highway Functions and
Classification 35
Design Elements 39 3
.6 Closing Comments 62 References 63
Problems 64
1 . 6
1 . 7
1 . 8
References 15
2 Road User and Vehicle
Characteristics 17
Components 17 2
Applications 31 2
Problems 34
Devices 65
4 .5 Special Types of Control 93
4 .6 Summary and Conclusion 94
References 94
Problems 94
Speed, and Density 103 5
.4 Closing Comments 105 References 105
Problems 105
iv CONTENTS
i i
Theory 107 6 .1 Basic Models of Uninterrupted Flow 107
6 .2 Queueing Theory 112
6 .3 Shock-Wave Theory and Applications 117
6 .4 Characteristics of Interrupted Flow 119
6 .5 Closing Comments 119
References 120
Problems 120
7 .1 Overview of Probability Functions
and Statistics 123
Applications 125 7
7 . 5 Addition of Random Variables 129
7 . 6 The Binomial Distribution Related to the
Bernoulli and Normal Distributions 131
7 . 7 The Poisson Distribution 133
7 .8 Hypothesis Testing 134
7 .9 Summary and Closing Comments 144
References 146
Problems 146
Methodologies 148 8 .1 Applications of Traffic Data 148
8 .2 Types of Studies 149
83 Data Collection Methodologies 150 8
. 4 Data Reduction 159
8 .6 Aerial Photography and Digitizing
Technology 159 8
References 163
Problems 163
9 .
9 . 3 Volume Characteristics 169
9 . 4 Intersection Volume Studies 174 c
9 . 5 Limited Network Volume Studies 176
9 .6 Statewide Counting Programs 184
9 .7 Specialized Counting Studies 189
9 .8 Closing Comments 195
References 195
Problems 195
10.1 Introduction 198
10.2 Spot Speed Studies 199 10.3 Travel-Time Studies 211
10.4 Intersection Delay Studies 218 10.5 Closing Comments 222 References 222
Problems 223
Statistics, and Programs 225 11.1 Introduction 225
11.2 Approaches to Highway Safety 227 11.3 Accident Data Collection and Record
Systems 230 11.4 Accident Statistics 234
11.5 Site Analysis 240 1
*
Problems 248
12 Parking 250 12.1 Introduction 250
12.2 Parking Generation and Supply Needs 250 12.3 Parking Studies and Characteristics 254 12.4 Design Aspects of Parking Facilities 263 12.5 Parking Programs 270 12.6 Closing Comments 271 References 272
Problems 272
13 Fundamental Concepts for Uninterrupted Flow Facilities 275
13.1 Types of Uninterrupted Flow Facilities 275 13.2 The Highway Capacity Manual 276 13.3 The Capacity Concept 277 13.4 The Level of Service Concept 278 13.5 Service Flow Rates and Service Volumes 281
13.6 The v/c Ratio and Its Use in Capacity Analysis 282
ONTENTS v
13.8 Closing Comments 283 References 283
Problems 284
14.1 Facility Types 285 14.2 Basic Freeway and Multilane Highway
Characteristics 286
14.3 Analysis Methodologies for Basic Freeway Sections and Multilane Highways 291 .
14.4 Sample Problems 303 14.5 Calibration Speed-Flow-Density Curves 309 14.6 Calibrating Passenger-Car Equivalents 309 14.7 Calibrating the Driver Population Factor 312 14.8 Adjustment Factors to Free-Row Speed 313 14.9 Software 313
14.10 Source Documents 313
References 313
Problems 314
5 Weaving, Merging, and Diverging Movements on Freeways and Multilane Highways 316
15.1 Turbulence Areas on Freeways and Multilane Highways 316
15.2 Level-of-Service Criteria 317
15.6 Basic Characteristics of Merge and Diverge Segment Analysis 333
15.7 Computational Procedures for Merge and Diverge Segments 335
15.8 Sample Problems in Weaving, Merging, and Diverging Analysis 342
15.9 Analysis of Freeway Facilities 352 References 353
Problems 354
16.2 Design Standards 363 16.3 Passing Sight Distance on Two-Lane
Highways 365
16.4 Capacity and Level-of-Service Analysis of Two-Lane Rural Highways 366
16.5 Sample Problems in Analysis of Rural Two-Lane Highways 37T
16.6 The Impact of Passing and Truck Climbing Lanes 384
16.7 Summary 387 References 387
Problems 387
17 Signing and Marking for Freeways and Rural Highways 389
17.1 Traffic Markings on Freeways and Rural Highways 389
1-7 .2 Establishing and Posting of Speed Limits 394
17.3 Guide Signing of Freeways and Rural Highways 396
17.4 Other Signs on Freeways and Rural Highways 404
References 405
Problems 407
Part 4 The Intersection 409
( Ts ) The Hierarchy of Intersection ,v \ V9 v> Control 410 v-' L'
18.1 Level I Control: Basic Rules
of the Road 411
Control 413
Control Signals 417 18.4 Closing Comments 432 References 432
Problems 432
19.1 Intersection Design Objectives and Considerations 437
19.2 A Basic Starting Point: Sizing the Intersection 438
19 3 Intersection Channelization 441
19.4 Special Situations at Intersections 443 19.5 Street Hardware for Signalized
Intersections 454
Problems 459
v t Signalization 461 20.1 Terms and Definitions 461
20.2 Discharge Headways, Saturation Flow, Lost Times, and Capacity 465
20.3 The Critical-Lane and Time-Budget Concepts 469
20.4 The Concept of Left-Turn (and Right-Tum) Equivalency 474
20.5 Delay as a Measure of Effectiveness 476 20.6 Overview 485
References 486
Problems 486
Fundamentals of Signal Timing and Design: Pretimed Signals 489
21.1 Development of Signal Phase Plans 490 21.2 Determining Vehicular Signal
Requirements 503 21.3 Determining Pedestrian Signal
Requirements 508 21.4 Compound Signal Timing 511 21.5 Sample Signal Timing Applications 511 21.6 References 522
References 522
Problems 522
Fundamentals of Signal Timing: Actuated Signals 526
22.1 Types of Actuated Control 527 22.2 Detectors and Detection 528
22.3 Actuated Control Features and
Operation 529 22.4 Actuated Signal Timing and Design 531 22.5 Examples in Actuated Signal
Design and Timing 537 References 542
Problems 542
23 Critical Movement Analysis of Signalized Intersections 545
23.1 The TRB Circular 212 Methodology 546 23.2 A Critical Movement Approach to Signalized
Intersection Analysis 546 23.3 Sample Problems Using Critical Movement
Analysis 558 23.4 Closing Comments 570 References 570
Problems 571
24.3 The Basic Model 579
24.4 A "Simple" Sample Problem 598 24.5 Complexities 605 24.6 Calibration Issues 610
24.7 Summary 615 References 615
Problems 615
25 Intelligent Transportation Systems in Support of Traffic Management and Control 620
25.1 ITS Standards 621
25.3 ITS Organizations and Sources of Information 622
25,4 ITS-Related Commercial Routing and Delivery 623
25.5 Sensing Traffic by Virtual and Other Detectors 623
25.6 Traffic Control in an ITS
Environment 624
25.7 How Fast Is Fast Enough? 629 25.8 Emerging Issues 630 25.9 Summary 631 Problems 631
26 Signal Coordination for Arterials and Networks: Undersatu rated
Conditions 632
26.3 Bandwidth Concepts 636 26.4 The Effect of Queued Vehicles
at Signals 638 26.5 Signal Progression for Two-Way Streets
and Networks 640
26.6 Common Types of Progression 646 26.7 Software for Doing Signal
Progression 650 26.8 Closing Comments 656 References 657 o
Problems 658
ONTENTS vii
Conditions 663
27.2 Root Causes of Congestion and Oversaturation 664
27.3 Overall Approaches to Address Oversaturation 665
27.4 Classification 666
27.5 Metering Plans 667 27.6 Signal Remedies 669 27.7 Variations in Demand
and Capacity 673 27.8 Summary and Further
Readings 676 References 677
28.1 Arterial Planning Issues and Approaches 678
28.2 Multimodal Performance
Problems 684
29 Planning, Design, and Operation of Streets and Artenals 686
29.1 Kramer's Concept of an Ideal Suburban
Arterial 687
29.2 Principles Guiding Local Streets 688 29.3 Access Management 688 29.4 Balanced Streets and Complete Streets 691 29.5 Traffic Calming 694 29.6 Roundabouts 698
29.7 Netwoik Issues 698
Problems 707
30 Traffic Impact Analysis 708
30.1 Scope of This Chapter 709 30.2 An Overview of the Process 709
30.3 Tools, Methods, and Metrics 712
30.4 Case Sliidy 1: Driveway Location 714 30.5 Case Study 2: Most Segments of a Traffic
Impact Analysis 715 30.6 Summay 726 References 726
Problems 726
Index 728
'
s
"lifeblood circulation system." Our complex system of roads and highways, railroads, airports and airlines, waterways, and urban transit systems provides for the movement of people and goods within and between our densest urban cities and the most remote outposts of the nation. Without the ability to travel and to transport goods, society must be stmctured around small self-sufficient communities, each of which produces food and material for all of its needs locally and disposes of its wastes in a similar manner. The benefits of economic specialization and mass production are possible only where transportation exists to move needed materials of production to centralized loca- tions, and finished products to widely dispersed consumers.
Traffic engineering deals with one critical element of the transportation system: streets and highways, and their use by vehicles. This vast national system provides mobility and access for individuals in private autos and for goods in trucks of various sizes and forms, and facilitates public transport by supporting buses, bicycles, and pedestrians.
Because the transportation system is such a critical part of our public infrastmcture, the traffic engineer is involved in a wide range of issues, often in a very public setting, and must bring a wide range of skills to the table to be effective. Traffic engineers must have an appreciation for and understanding of planning, design, management, construction, operation, control, and system optimization. All of these functions involve traffic engineers at some level.
This text focuses on the key engineering skills required to practice traffic engineering in a modern setting. This is the fourth edition of this textbook. It includes material on the lat-
est standards and criteria of the Manual on Uniform Traffic Control Devices (2003 Edition and forthcoming 2010 Edition), the Policy on Geometric Design of Highways and Streets (2004 Edition), the Highway Capacity Manual (2000 Edition and forthcoming 2010 Edition),
and other critical
references. It also presents both fundamental theory and a broad range of applications to modern problems.
The text is organized in five major functional parts:
. Part I-Traffic Components and Characteristics
. Part 2-Traffic Studies and Programs
. Part 3-Freeways and Rural Highways
. Part 4-The Intersection
. Part 5-Arterials , Networks, and Systems
This text can be used for an undergraduate survey course, or
for more detailed graduate courses. At Polytechnic Institute of
"
New York University, it is used for two undergraduate courses and a series of three graduate courses.
As in previous editions, the text contains many sample problems and illustrations that can be used in conjunction with course material. A solutions manual is available
. The authors
hope that practicing professionals and students find this text useful and informative
.
What's New in This Edition
This edition of the textbook adds a significant amount of material, including,
but not limited to:
2 . New chapters on Traffic Flow Theory, Analysis of
Arterials in a Multimodal Setting, Critical Movement
Analysis of Signalized Intersections, and Traffic
Impact Studies.
3 . Material from the latest editions of key traffic engi-
neering references, including the Traffic Engineering Handbook, the Manual of Uniform Traffic Control
7
-I m
Devices, the Traffic Signal Timing Handbook; and the Policy on Geometric Design of Highways and Streets.
4 . Substantial material from forthcoming new editions
of the Highway Capacity Manual (2010) and Manual of Uniform Traffic Control Devices (2010), which were obtained from research documents, draft
materials, and other source documents has been
included. Since some of this materia! has not yet been officially adopted, it provides a preview, but not final information on these standard documents.
5 . New material on actuated signal systems and timing.
6 . New material on coordination of signal systems.
7 .
demonstration solutions using current software packages.
Roger P. Roess
Elena S. Prassas
William R . McShane
The Institute of Transportation Engineers defines traffic engineering as a subset of transportation engineering as follows []]:
Transportation engineering is the application of tech- nology and scientific principles to the planning, func- tional design, operation, and management of facilities for any mode of transportation in order to provide for the safe, rapid, comfortable, convenient, economical, and environmentally compatible movement of people and goods.
and:
Traffic engineering is that phase of transportation engi- neering which deals with the planning, geometric design and traffic operations of roads, streets, and high- ways, their networks, terminals, abutting lands, and relationships with other modes of transportation.
These definitions represent a broadening of the profession to include multimodal transportation systems and options, and to include a variety of objectives in addition to the traditional goals of safety and efficiency.
1 . 1 .1 Safety: The Primary Objective
The principal goal of the traffic engineer remains the provision of a safe system for highway traffic. This is no small concern.
In
recent years, fatalities on U.S. highways have ranged between 40,000 and 43,000 per year. Although this is a reduction from the highs experienced in the 1970s, when highway fatalities reached more than 55,000 per year, it continues to represent a staggering number. Rising fuel prices in 2008 and 2009 have had an impact on both fatalities and vehicle-miles travelled.
In
2008, fatalities were reduced to 37,261, the first time the number
dipped below 40,000 in many years. Some of this was due to a reduction in vehicle-miles travelled, which dipped under 3
.0 trillion miles after two years over this level. It remains to be seen whether this reduction is sustainable or whether fatalities
will rise once again when (and if) the fuel cost issues are resolved. One point, however, remains: More Americans have been killed on U.S. highways than in all of the wars in which the nation has participated, including the Civil War.
Although total highway fatalities per year have remained relatively stable over the past two decades,
accident
rates based on vehicle-miles traveled have consistently declined. That is because U.S. motorists continue to drive
more miles each year. With a stable total number of fatalities, the increasing number of annual vehicle-miles traveled pro- duces a declining fatality rate. This trend will also be affected by the decrease in vehicle use in 2008 and 2009.
1
;;r-
2 CHAPTER 1 INTRODUCTION TO TRAFFIC ENGINEERING
Improvements in fatality rates reflect a number of trends, many of which traffic engineers have been instrumental in implementing. Stronger efforts to remove dangerous drivers from the road have yielded significant dividends in safety. Driving under the influence (DUI) and driving while intoxicated (DWI) offenses are more strictly enforced, and licenses are suspended or revoked more easily as a result of DUI/DWI convictions, poor accident record, and/or poor violations record. Vehicle design has greatly improved (encouraged by several acts of Congress requiring certain improvements). Today
's vehicles
feature padded dashboards, collapsible steering columns, seat belts with shoulder harnesses, air bags (some vehicles now have as many as eight), and antilock braking systems. Highway design has improved through the development and use of advanced barrier systems for medians and roadside areas. Traffic control systems communicate better and faster, and surveillance systems can alert authorities to accidents and break- downs in the system.
Despite this, however, approximately 40,000 people per year still die in traffic accidents. The objective of safe travel is always number one and is never finished for the traffic engineer.
1 . 1
The definitions of transportation and traffic engineering high- light additional objectives:
. Speed
. Comfort
. Convenience
. Economy
. Environmental compatibility
Most of these are self-evident desires of the traveler. Most of
us want our trips to be fast, comfortable, convenient, cheap, and in harmony with the environment. All of these objectives are also relative and must be balanced against each other and against the primary objective of safety.
Although speed of travel is much to be desired, it is limited by transportation technology, human characteristics, and the need to provide safety. Comfort and convenience are generic terms and mean different things to different people. Comfort involves the physical characteristics of vehicles and roadways, and it is influenced by our perception of safety. Convenience relates more to the ease with which trips are made and the ability of transport systems to accommodate all of our travel needs at appropriate times. Economy is also relative. There is little in modem transportation systems that can be termed
"cheap. "
which are provided through general and user taxes and fees .
Nevertheless, every engineer, regardless of discipline, is called
on to provide the best possible systems for the money.
Harmony with the environment is a complex issue that has become more important over time. All transportation systems have some negative impacts on the environment
. All
produce air and noise pollution in some forms, and all utilize valuable land resources. In many modem cities
, transportation systems use as much as 25% of the total land area
. "Harmony"
is achieved when transportation systems are designed to minimize negative environmental impacts, and where system architecture provides for aesthetically pleasing facilities that "fit in" with their surroundings.
The traffic engineer is tasked with all of these goals and objectives and with making the appropriate trade-offs to opti- mize both the transportation systems and the use of public funds to build, maintain, and operate them.
1 . 1
Responsibility, Ethics, and Liability in Traffic Engineering
The traffic engineer has a very special relationship with the public at large. Perhaps more than any other type of engineer, the traffic engineer deals with the daily safety of a large seg- ment of the public. Although i t can be argued that any engineer who designs a product has this responsibility, few engineers have so many people using their product so routinely and frequently and depending on it so totally. Therefore,
the traffic
engineer also has a special obligation…