Traffic Engineering

Contents
Preface xiii
1 Introduction to Traffic Engineering 1
1.1 Traffic Engineering as a Profession 1
1.1.1 Safety: The Primary Objective 1
1.1.2 Other Objectives 2
1.1.3 Responsibility, Ethics, and Liability in Traffic Engineering 2
1.2 Transportation Systems and Their Function 3
1.2.1 The Nature of Transportation Demand 4
1.2.2 Concepts of Mobility and Accessibility 5
1.2.3 People, Goods, and Vehicles 6
1.2.4 Transportation Modes 6
1.3 Highway Legislation and History in the United States 8
1.3.1 The National Pike and the States’ Rights Issue 8
1.3.2 Key Legislative Milestones 9
1.3.3 The National System of Interstate and Defense Highways 11
1.4 Elements of Traffic Engineering 12
1.5 Modern Problems for the Traffic Engineer 13
1.6 Standard References for the Traffic Engineer 14
1.7 Metric versus U.S. Units 15
1.8 Closing Comments 15
References 15

Part 1 Traffic Components and Characteristics 16
2 Road User and Vehicle Characteristics 17
2.1 Overview of Traffic Stream Components 17
2.1.1 Dealing with Diversity 17
2.1.2 Addressing Diversity through Uniformity 18
2.2 Road Users 18
2.2.1 Visual Characteristics of Drivers 19
2.2.2 Important Visual Deficits 20
2.2.3 Perception-Reaction Time 20
2.2.4 Pedestrian Characteristics 22
2.2.5 Impacts of Drugs and Alcohol on Road Users 24
2.2.6 Impacts of Aging on Road Users 25
2.2.7 Psychological, Personality, and Related Factors 25
2.3 Vehicles 25
2.3.1 Concept of the Design Vehicle 26
2.3.2 Turning Characteristics of Vehicles 27
2.3.3 Braking Characteristics 29
2.3.4 Acceleration Characteristics 30
2.4 Total Stopping Distance and Applications 31
2.4.1 Safe Stopping Sight Distance 31
2.4.2 Decision Sight Distance 32
2.4.3 Other Sight Distance Applications 33
2.4.4 Change (Yellow) and Clearance (All Red) Intervals for a Traffic Signal 33
2.5 Closing Comments 33
References 33
Problems 34

3 Roadways and Their Geometric Characteristics 35
3.1 Highway Functions and Classification 35
3.1.1 Trip Functions 35
3.1.2 Highway Classification 36
3.1.3 Preserving the Function of a Facility 38
3.2 Introduction to Highway Design Elements 39
3.2.1 Horizontal Alignment 39
3.2.2 Vertical Alignment 39
3.2.3 Cross-Sectional Elements 40
3.2.4 Surveying and Stationing 40
3.3 Horizontal Alignment of Highways 40
3.3.1 Quantifying the Severity of Horizontal Curves: Radius and Degree of Curvature 40
3.3.2 Review of Trigonometric Functions 41
3.3.3 Critical Characteristics of Horizontal Curves 41
3.3.4 Superelevation of Horizontal Curves 44
3.3.5 Spiral Transition Curves 47
3.3.6 Sight Distance on Horizontal Curves 51
3.3.7 Compound Horizontal Curves 52
3.3.8 Reverse Horizontal Curves 52
3.4 Vertical Alignment of Highways 53
3.4.1 Grades 53
3.4.2 Geometric Characteristics of Vertical Curves 56
3.4.3 Sight Distance on Vertical Curves 58
3.4.4 Other Minimum Controls on Length of Vertical Curves 59
3.4.5 Some Design Guidelines for Vertical Curves 59
3.5 Cross-Section Elements of Highways 60
3.5.1 Travel Lanes and Pavement 60
3.5.2 Shoulders 61
3.5.3 Side-Slopes for Cuts and Embankments 61
3.5.4 Guardrail 61
3.6 Closing Comments 62
References 63
Problems 64

4 Introduction to Traffic Control Devices 65
4.1 The Manual on Uniform Traffic Control Devices 65
4.1.1 History and Background 65
4.1.2 General Principles of the MUTCD 66
4.1.3 Contents of the MUTCD 67
4.1.4 Legal Aspects of the MUTCD 67
4.1.5 Communicating with the Driver 68
4.2 Traffic Markings 69
4.2.1 Colors and Patterns 69
4.2.2 Longitudinal Markings 69
4.2.3 Transverse Markings 71
4.2.4 Object Markers 73
4.2.5 Delineators 73
4.3 Traffic Signs 74
4.3.1 Regulatory Signs 75
4.3.2 Warning Signs 78
4.3.3 Guide Signs 80
4.4 Traffic Signals 87
4.4.1 Traffic Control Signals 87
4.4.2 Pedestrian Signals 91
4.4.3 Other Traffic Signals 93
4.4.4 Traffic Signal Controllers 93
4.5 Special Types of Control 93
4.6 Summary and Conclusion 94
References 94
Problems 94

5 Traffic Stream Characteristics 95
5.1 Types of Facilities 95
5.2 Traffic Stream Parameters 96
5.2.1 Volume and Rate of Flow 96
5.2.2 Speed and Travel Time 100
5.2.3 Density and Occupancy 101
5.2.4 Spacing and Headway: Microscopic Parameters 102
5.3 Relationships among Flow Rate, Speed, and Density 103
5.4 Closing Comments 105
References 105
Problems 105

6 Introduction to Traffic Flow Theory 107
6.1 Basic Models of Uninterrupted Flow 107
6.1.1 Historical Background 107
6.1.2 Deriving Speed–Flow and Density–Flow Curves from a Speed-Density Curve 108
6.1.3 Determining Capacity from Speed-Flow-Density Relationships 109
6.1.4 Modern Uninterrupted Flow Characteristics 109
6.1.5 Calibrating a Speed-Flow-Density Relationship 111
6.1.6 Curve Fitting 112
6.2 Queueing Theory 112
6.2.1 One Capacity or Two? An Illustration Using Deterministic Queueing 113
6.2.2 A Problem with Deterministic Queueing 114
6.2.3 The Basic Approach to Queueing Analysis: Random Patterns 115
6.3 Shock-Wave Theory and Applications 117
6.3.1 Different Flow-Density Curves 117
6.3.2 Rate of growth 118
6.4 Characteristics of Interrupted Flow 119
6.5 Closing Comments 119
References 120
Problems 120

Part 2 Traffic Studies and Programs 121
7 Statistical Applications in Traffic Engineering 122
7.1 Overview of Probability Functions and Statistics 123
7.1.1 Discrete versus Continuous Functions 123
7.1.2 Randomness and Distributions Describing Randomness 123
7.1.3 Organizing Data 123
7.1.4 Common Statistical Estimators 124
7.2 The Normal Distribution and Its Applications 125
7.2.1 The Standard Normal Distribution 126
7.2.2 Important Characteristics of the Normal Distribution Function 128
7.3 Confidence Bounds 128
7.4 Sample Size Computations 129
7.5 Addition of Random Variables 129
7.5.1 The Central Limit Theorem 130
7.6 The Binomial Distribution Related to the Bernoulli and Normal Distributions 131
7.6.1 Bernoulli and the Binomial Distribution 131
7.6.2 Asking People Questions: Survey Results 133
7.6.3 The Binomial and the Normal Distributions 133
7.7 The Poisson Distribution 133
7.8 Hypothesis Testing 134
7.8.1 Before-and-After Tests with Two Distinct Choices 135
7.8.2 Before-and-After Tests with Generalized Alternative Hypothesis 137
7.8.3 Other Useful Statistical Tests 138
7.9 Summary and Closing Comments 144
References 146
Problems 146

8 Traffic Data Collection and Reduction Methodologies 148
8.1 Applications of Traffic Data 148
8.2 Types of Studies 149
8.3 Data Collection Methodologies 150
8.3.1 Manual Data Collection Techniques 150
8.3.2 Portable Traffic Data Equipment/Semiautomated Studies 155
8.3.3 Permanent Detectors 156
8.4 Data Reduction 159
8.5 Cell Phones 159
8.6 Aerial Photography and Digitizing Technology 159
8.7 Interview Studies 162
8.7.1 Comprehensive Home Interview Studies 162
8.7.2 Roadside Interview Studies 162
8.7.3 Destination-Based Interview Studies 162
8.7.4 Statistical Issues 163
8.8 Concluding Comments 163
References 163
Problems 163

9 Volume Studies and Characteristics 165
9.1 Critical Parameters 165
9.2 Volume, Demand, and Capacity 166
9.3 Volume Characteristics 169
9.3.1 Hourly Traffic Variation Patterns: The Phenomenon of the Peak Hour 169
9.3.2 Subhourly Variation Patterns: Flow Rates Versus Volumes 172
9.3.3 Daily Variation Patterns 172
9.3.4 Monthly or Seasonal Variation Patterns 172
9.3.5 Some Final Thoughts on Volume Variation Patterns 172
9.4 Intersection Volume Studies 174
9.4.1 Arrival Versus Departure Volumes: A Key Issue for Intersection Studies 174
9.4.2 Special Considerations for Signalized Intersections 176
9.4.3 Presentation of Intersection Volume Data 176
9.5 Limited Network Volume Studies 176
9.5.1 Control Counts 178
9.5.2 Coverage Counts 179
9.5.3 An Illustrative Study 179
9.6 Statewide Counting Programs 184
9.6.1 Calibrating Daily Variation Factors 185
9.6.2 Calibrating Monthly Variation Factors 185
9.6.3 Grouping Data from Control Count Locations 187
9.6.4 Using the Results 187
9.7 Specialized Counting Studies 189
9.7.1 Origin and Destination Counts 189
9.7.2 Cordon Counts 192
9.7.3 Screen-Line Counts 193
9.8 Closing Comments 194
References 194
Problems 194

10 Speed, Travel Time, and Delay Studies 197
10.1 Introduction 197
10.2 Spot Speed Studies 198
10.2.1 Speed Definitions of Interest 198
10.2.2 Uses of Spot Speed Data 198
10.2.3 Analysis of Spot Speed Data 199
10.3 Travel-Time Studies 210
10.3.1 Travel-Time Data Along an Arterial: An Example of the Statistics of Travel Times 211
10.3.2 Overriding Default Values: Another Example of Statistical Analysis of Travel-Time Data 213
10.3.3 Travel-Time Displays 215
10.4 Intersection Delay Studies 216
10.5 Closing Comments 220
References 220
Problems 220

11 Highway Traffic Safety: Studies, Statistics, and Programs 222
11.1 Introduction 222
11.2 Approaches to Highway Safety 224
11.2.1 Exposure Control 224
11.2.2 Accident Risk Control/Accident Prevention 225
11.2.3 Behavior Modification 225
11.2.4 Injury Control 225
11.2.5 Postinjury Management 226
11.2.6 Planning Actions to Implement Policy Strategies 226
11.2.7 National Policy Initiatives 227
11.3 Accident Data Collection and Record Systems 227
11.3.1 Accident Reporting 228
11.3.2 Manual Filing Systems 228
11.3.3 Computer Record Systems 229
11.4 Accident Statistics 231
11.4.1 Types of Statistics 231
11.4.2 Accident Rates 231
11.4.3 Statistical Displays and Their Use 233
11.4.4 Identifying High-Accident Locations 234
11.4.5 Before-and-After Accident Analysis 235
11.5 Site Analysis 237
11.5.1 Collision Diagrams 238
11.5.2 Condition Diagrams 239
11.5.3 Interpretation of Condition and Collision Diagrams 240
11.6 Development of Countermeasures 241
11.7 Closing Comments 241
References 241
Problems 245

12 Parking 247
12.1 Introduction 247
12.2 Parking Generation and Supply Needs 247
12.2.1 Parking Generation 248
12.2.2 Zoning Regulations 251
12.3 Parking Studies and Characteristics 251
12.3.1 Proximity: How Far Will Parkers Walk? 251
12.3.2 Parking Inventories 254
12.3.3 Accumulation and Duration 256
12.3.4 Other Types of Parking Studies 259
12.4 Design Aspects of Parking Facilities 260
12.4.1 Some Basic Parking Dimensions 261
12.4.2 Parking Modules 262
12.4.3 Separating Small and Large Vehicle Areas 263
12.4.4 Parking Garages 266
12.5 Parking Programs 267
12.6 Closing Comments 268
References 269
Problems 269

Part 3 Freeways and Rural Highways 270
13 Fundamental Concepts for Uninterrupted Flow Facilities 271
13.1 Types of Uninterrupted Flow Facilities 271
13.2 The Highway Capacity Manual 272
13.3 The Capacity Concept 273
13.3.1 The Current Definition 273
13.3.2 Historical Background 273
13.3.3 Current Values of Capacity for Uninterrupted Flow Facilities 274
13.4 The Level of Service Concept 274
13.4.1 Historical Development of the Level of Service Concept 274
13.4.2 The Fourth Edition of the HCM (2000): The Current Definition 275
13.4.3 Incorporating Road User Perceptions into Levels of Service 276
13.5 Service Flow Rates and Service Volumes 277
13.6 The v/c Ratio and Its Use in Capacity Analysis 278
13.7 Problems in Use of Level of Service 279
13.8 Closing Comments 279
References 279
Problems 280

14 Basic Freeway Segments and Multilane Highways 281
14.1 Facility Types 281
14.2 Basic Freeway and Multilane Highway Characteristics 282
14.2.1 Speed-Flow Characteristics 282
14.2.2 Levels of Service 282
14.2.3 Service Flow Rates and Capacity 286
14.3 Analysis Methodologies for Basic Freeway Sections and Multilane Highways 287
14.3.1 Types of Analysis 287
14.3.2 Determining the Free-Flow Speed 289
14.3.3 Determining the Heavy-Vehicle Factor 292
14.3.4 Determining the Driver Population Factor 299
14.4 Sample Problems 299
14.5 Calibration Speed-Flow-Density Curves 305
14.6 Calibrating Passenger Car Equivalents 305
14.6.1 Driver-Determined Equivalence 306
14.6.2 Equivalence Based on Constant Spacing 307
14.6.3 Equivalence Based on Constant Speed 308
14.6.4 Macroscopic Calibration of the Heavy-Vehicle Factor 308
14.6.5 Additional References on Heavy Vehicle Factors 308
14.7 Calibrating the Driver Population Factor 308
14.8 Adjustment Factors to Free-Flow Speed 309
14.9 Software 309
14.10 Source Documents 309
References 309
Problems 310

15 Weaving, Merging, and Diverging Movements on Freeways and Multilane Highways 312
15.1 Turbulence Areas on Freeways and Multilane Highways 312
15.2 Level-of-Service Criteria 313
15.3 A Common Point: Converting Demand Volumes 315
15.4 Weaving Segments: Basic Characteristics and Variables 315
15.4.1 Flows in a Weaving Area 316
15.4.2 Critical Geometric Variables 317
15.5 Computational Procedures for Weaving Area Analysis 321
15.5.1 Parameters Used in Weaving Segment Analysis 321
15.5.2 Volume Adjustment (Step 2) 321
15.5.3 Determining Configuration Characteristics (Step 3) 321
15.5.4 Determining the Maximum Weaving Length (Step 4) 323
15.5.5 Determine the Capacity of the Weaving Segment (Step 5) 324
15.5.6 Determining Total Lane-Changing Rates Within the Weaving Segment (Step 6) 325
15.5.7 Determining the Average Speed of Vehicles Within a Weaving Segment (Step 7) 327
15.5.8 Determining Density and Level of Service in a Weaving Segment (Step 8) 328
15.6 Basic Characteristics of Merge and Diverge Segment Analysis 328
15.7 Computational Procedures for Merge and Diverge Segments 329
15.7.1 Overview 329
15.7.2 Estimating Demand Flow Rates in Lanes 1 and 2 (Step 2) 331
15.7.3 Capacity Considerations 334
15.7.4 Determining Density and Level of Service in the Ramp Influence Area 335
15.7.5 Determining Expected Speed Measures 336
15.7.6 Special Cases 336
15.8 Sample Problems in Weaving, Merging, and Diverging Analysis 337
15.9 Analysis of Freeway Facilities 346
15.9.1 Segmenting the Freeway 346
15.9.2 Analysis Models 346
References 348
Problems 348

16 Two-Lane Highways 355
16.1 Introduction 355
16.2 Design Standards 357
16.3 Passing Sight Distance on Two-Lane Highways 359
16.4 Capacity and Level-of-Service Analysis of Two-Lane Rural Highways 360
16.4.1 Capacity 361
16.4.2 Level of Service 361
16.4.3 Types of Analysis 362
16.4.4 Free-Flow Speed 363
16.4.5 Estimating Demand Flow Rate 364
16.4.6 Estimating Average Travel Speed 371
16.4.7 Determining Percent Time Spent Following 371
16.5 Sample Problems in Analysis of Rural Two-Lane Highways 371
16.5.1 Analysis of a Class I Rural Two-Lane Highway in Rolling Terrain 371
16.5.2 Single-Direction Analysis of a Specific Grade 377
16.6 The Impact of Passing and Truck Climbing Lanes 378
16.6.1 Evaluating the Impact of Passing Lanes 378
16.6.2 Evaluating the Impact of Climbing Lanes 380
16.7 Summary 381
References 381
Problems 381

17 Signing and Marking for Freeways and Rural Highways 383
17.1 Traffic Markings on Freeways and Rural Highways 383
17.1.1 Freeway Markings 383
17.1.2 Rural Highway Markings 383
17.1.3 Ramp Junction Markings 385
17.2 Establishing and Posting of Speed Limits 388
17.3 Guide Signing of Freeways and Rural Highways 390
17.3.1 Reference Location Posts 390
17.3.2 Numbered Highway Systems 390
17.3.3 Exit Numbering Systems 392
17.3.4 Route Sign Assemblies 393
17.3.5 Freeway and Expressway Guide Signing 394
17.3.6 Guide Signing for Conventional Roads 397
17.4 Other Signs on Freeways and Rural Highways 398
References 399
Problems 401

Part 4 The Intersection 403
18 The Hierarchy of Intersection Control 404
18.1 Level I Control: Basic Rules of the Road 405
18.2 Level II Control: YIELD and STOP Control 407
18.2.1 Two-Way Stop Control 408
18.2.2 Yield Control 410
18.2.3 Multiway Stop Control 410
18.3 Level III Control: Traffic Control Signals 411
18.3.1 Advantages of Traffic Signal Control 411
18.3.2 Disadvantages of Traffic Signal Control 412
18.3.3 Warrants for Traffic Signals 412
18.3.4 Summary 421
18.3.5 A Sample Problem in Application of Signal Warrants 422
18.4 Closing Comments 426
References 426
Problems 426

19 Elements of Intersection Design and Layout 431
19.1 Intersection Design Objectives and Considerations 431
19.2 A Basic Starting Point: Sizing the Intersection 432
19.2.1 Unsignalized Intersections 432
19.2.2 Signalized Intersections 433
19.3 Intersection Channelization 435
19.3.1 General Principles 435
19.3.2 Some Examples 435
19.3.3 Channelizing Right Turns 437
19.4 Special Situations at Intersections 437
19.4.1 Intersections at Skewed Angles 437
19.4.2 T-Intersections: Opportunities for Creativity 440
19.4.3 Offset Intersections 441
19.4.4 Special Treatments for Heavy Left-Turn Movements 445
19.5 Street Hardware for Signalized Intersections 448
19.6 Closing Comments 453
References 453
Problems 453

20 Basic Principles of Intersection Signalization 455
20.1 Terms and Definitions 455
20.1.1 Components of a Signal Cycle 456
20.1.2 Types of Signal Operation 456
20.1.3 Treatment of Left Turns and Right Turns 457
20.2 Discharge Headways, Saturation Flow, Lost Times, and Capacity 459
20.2.1 Saturation Headway and Saturation Flow Rate 460
20.2.2 Start-Up Lost Time 460
20.2.3 Clearance Lost Time 460
20.2.4 Total Lost Time and the Concept of Effective GREEN Time 460
20.2.5 Capacity of an Intersection Lane or Lane Group 461
20.2.6 Notable Studies on Saturation Headways, Flow Rates, and Lost Times 462
20.3 The Critical-Lane and Time-Budget Concepts 463
20.3.1 The Maximum Sum of Critical-Lane Volumes: One View of Signalized Intersection Capacity 464
20.3.2 Finding an Appropriate Cycle Length 465
20.4 The Concept of Left-Turn (and Right-Turn) Equivalency 468
20.5 Delay as a Measure of Effectiveness 470
20.5.1 Types of Delay 470
20.5.2 Basic Theoretical Models of Delay 471
20.5.3 Inconsistencies in Random and Overflow Delay 477
20.5.4 Delay Models in the HCM 478
20.5.5 Examples in Delay Estimation 478
20.6 Overview 479
References 480
Problems 480

21 Fundamentals of Signal Timing and Design: Pretimed Signals 483
21.1 Development of Signal Phase Plans 484
21.1.1 Treatment of Left Turns 484
21.1.2 General Considerations in Signal Phasing 486
21.1.3 Phase and Ring Diagrams 486
21.1.4 Common Phase Plans and Their Use 486
21.1.5 Summary and Conclusion 496
21.2 Determining Vehicular Signal Requirements 496
21.2.1 Change and Clearance Intervals 496
21.2.2 Determining Lost Times 498
21.2.3 Determining the Sum of Critical-Lane Volumes 498
21.2.4 Determining the Desired Cycle Length 500
21.2.5 Splitting the Green 501
21.3 Determining Pedestrian Signal Requirements 501
21.4 Compound Signal Timing 503
21.5 Sample Signal Timing Applications 504
21.6 References 515
References 515
Problems 515

22 Fundamentals of Signal Timing: Actuated Signals 519
22.1 Types of Actuated Control 520
22.2 Detectors and Detection 521
22.3 Actuated Control Features and Operation 522
22.3.1 Actuated Controller Features 522
22.3.2 Actuated Controller Operation 523
22.4 Actuated Signal Timing and Design 524
22.4.1 Phase Plans 525
22.4.2 Minimum Green Times 525
22.4.3 Passage Time 526
22.4.4 Detector Location 527
22.4.5 Yellow and All-Red Intervals 527
22.4.6 Maximum Green Times and the Critical Cycle 528
22.4.7 Pedestrian Requirements for Actuated Signals 529
22.4.8 Dual-Entry Feature 529
22.4.9 Recall Features 529
22.5 Examples in Actuated Signal Design and Timing 530
References 535
Problems 535

23 Critical Movement Analysis of Signalized Intersections 538
23.1 The TRB Circular 212 Methodology 539
23.2 A Planning Approach to Signalized Intersection Analysis 539
23.2.1 Step 1: Identify Lane Geometry 539
23.2.2 Step 2: Identify Demand Volumes 539
23.2.3 Step 3: Identify Phasing 540
23.2.4 Step 4: Left-Turn Check 540
23.2.5 Step 5: Assignment of Lane Volumes 540
23.2.6 Step 6: Determining Critical-Lane Volumes and the Sum of Critical-Lane Volumes 541
23.2.7 Step 7: Determine Probable Level of Service 541
23.2.8 Sample Problem: Planning Application 541
23.3 An Operations and Design Approach to Signalized Intersection Analysis 544
23.3.1 Steps 1 Through 3 545
23.3.2 Step 4: Convert Demand Volumes to Equivalent Passenger-Car Volumes 545
23.3.3 Step 5: Convert Passenger-Car Equivalents to Through-Car Equivalents 546
23.3.4 Step 6: Converting Through-Car Equivalents Under Prevailing Conditions to Through-Car Equivalents Under Ideal Conditions 547
23.3.5 Assigning Lane Flow Rates 548
23.3.6 Finding Critical-Lane Flow Rates for Each Signal Phase 548
23.3.7 Capacity and v/c Ratios 549
23.3.8 Delay and Level of Service 550
23.3.9 A Worksheet for Critical Movement Analysis 552
23.3.10 Summary 556
23.4 Sample Problems Using Critical Movement Analysis 556
23.4.1 Sample Problem 1: A Relatively Simple Problem 556
23.4.2 Sample Problem 2: Example with Compound Phasing 564
23.5 Closing Comments 568
References 568
Problems 569

24 Analysis of Signalized Intersections 571
24.1 Introduction 571
24.2 Conceptual Framework for the HCM 2010 Methodology 572
24.2.1 The Critical-Lane Group Concept 572
24.2.2 The v/s Ratio as a Measure of Demand 573
24.2.3 Capacity and Saturation Flow Rate Concepts 573
24.2.4 Level-of-Service Concepts and Criteria 575
24.2.5 Effective Green Times and Lost Times 576
24.3 The Basic Model 577
24.3.1 Model Structure 577
24.3.2 Analysis Time Periods 577
24.3.3 Input 579
24.3.4 Movement Groups, Lane Groups, and Demand Volume Adjustment 583
24.3.5 Estimating the Saturation Flow Rate for Each Lane Group 583
24.3.6 Determine Lane Group Capacities and v/c Ratios 589
24.3.7 Estimating Delay and Level of Service 591
24.3.8 Interpreting the Results of Signalized Intersection Analysis 595
24.4 A “Simple” Sample Problem 596
24.4.1 Input 597
24.4.2 Volume Adjustment 597
24.4.3 Saturation Flow Rate Estimation 597
24.4.4 Capacity Analysis 598
24.4.5 Delay Estimation and Level of Service 599
24.4.6 Analysis 601
24.4.7 What If There Is a d3? 601
24.5 Complexities 603
24.5.1 Permitted Left Turns 603
24.5.2 Modeling Compound Phasing 606
24.5.3 Altering Signal Timings Based on v/s Ratios 606
24.5.4 Analysis of Actuated Signals 608
24.6 Calibration Issues 608
24.6.1 Measuring Prevailing Saturation Flow Rates 609
24.6.2 Measuring Base Saturation Flow Rates 609
24.6.3 Measuring Startup Lost Time 609
24.6.4 An Example of Measuring Saturation Flow Rates and Startup Lost Times 609
24.6.5 Calibrating Adjustment Factors 611
24.6.6 Normalizing Signalized Intersection Analysis 612
24.7 Summary 613
References 613
Problems 613

25 Intelligent Transportation Systems in Support of Traffic Management and Control 618
25.1 ITS Standards 619
25.2 National ITS Architecture 620
25.3 ITS Organizations and Sources of Information 620
25.4 ITS-Related Commercial Routing and Delivery 621
25.5 Sensing Traffic by Virtual and Other Detectors 621
25.6 Traffic Control in an ITS Environment 622
25.7 How Fast Is Fast Enough? 627
25.8 Emerging Issues 628
25.9 Summary 629
Problems 629

26 Signal Coordination for Arterials and Networks: Undersaturated Conditions 630
26.1 Basic Principles of Signal Coordination 630
26.1.1 A Key Requirement: Common Cycle Length 630
26.1.2 The Time-Space Diagram and Ideal Offsets 630
26.2 Signal Progression on One-Way Streets 632
26.2.1 Determining Ideal Offsets 632
26.2.2 Potential Problems 634
26.3 Bandwidth Concepts 634
26.3.1 Bandwidth Efficiency 635
26.3.2 Bandwidth Capacity 635
26.4 The Effect of Queued Vehicles at Signals 636
26.5 Signal Progression for Two-Way Streets and Networks 638
26.5.1 Offsets on a Two-Way Street 639
26.5.2 Network Closure 640
26.5.3 Finding Compromise Solutions 642
26.6 Common Types of Progression 644
26.6.1 Progression Terminology 644
26.6.2 The Alternate Progression 645
26.6.3 The Double-Alternating Progression 646
26.6.4 The Simultaneous Progression 646
26.6.5 Insights from the Importance of Signal Spacing and Cycle Length 647
26.7 Software for Doing Signal Progression 648
26.7.1 Bandwidth-Based Solutions 649
26.7.2 Synchro 652
26.8 Closing Comments 654
References 655
Problems 656

27 Signal Coordination for Arterials and Networks: Oversaturated Conditions 661
27.1 System Objectives for Oversaturated Conditions 661
27.2 Root Causes of Congestion and Oversaturation 662
27.3 Overall Approaches to Address Oversaturation 663
27.4 Classification 664
27.5 Metering Plans 665
27.6 Signal Remedies 667
27.6.1 Responsive/Adaptive Phase Duration Changes 667
27.6.2 Shorter Cycle Lengths 667
27.6.3 Equity Offsets 668
27.6.4 Imbalanced Split 669
27.6.5 Phase Reservice 671
27.6.6 Pedestrian Minima Provided Only Upon Request 671
27.7 Variations in Demand and Capacity 671
27.7.1 An Illustration of the Effects of Demand and Capacity Variability on Delay 672
27.7.2 Practical Implications 672
27.7.3 A Closing Note on This Topic 674
27.8 Summary and Further Readings 674
References 675

28 Analysis of Streets in a Multimodal Context 676
28.1 Arterial Planning Issues and Approaches 676
28.2 Multimodal Performance Assessment 677
28.2.1 Bicycle Level of Service 678
28.2.2 Pedestrian Level of Service 679
28.2.3 Bus Level of Service 679
28.2.4 Automobile Level of Service 679
28.2.5 Florida Quality/Level of Service Handbook 681
28.3 Summary 681
References 682
Problems 682

29 Planning, Design, and Operation of Streets and Arterials 684
29.1 Kramer’s Concept of an Ideal Suburban Arterial 685
29.2 Principles Guiding Local Streets 686
29.3 Access Management 686
29.3.1 Primary Operations Measures in Access Management 686
29.3.2 Proper Median Treatments 687
29.3.3 Control Number, Placement, and Design of Driveways 687
29.3.4 Separation of Functions 689
29.4 Balanced Streets and Complete Streets 689
29.5 Traffic Calming 692
29.5.1 Overview 692
29.5.2 Illustrative Techniques 692
29.5.3 Impacts and Effectiveness of Traffic Calming Measures 695
29.6 Roundabouts 696
29.7 Network Issues 696
29.7.1 One-Way Street Systems 696
29.7.2 Special Use Lanes 698
29.8 Special Cases 699
29.8.1 Transitions from One Signal Plan to Another 700
29.8.2 Coordinating Multiphase Signals 700
29.8.3 Multiple and Sub-Multiple Cycle Lengths 701
29.8.4 The Diamond Interchange 702
29.9 Summary 704
References 704
Problems 705

30 Traffic Impact Analysis 706
30.1 Scope of This Chapter 707
30.2 An Overview of the Process 707
30.3 Tools, Methods, and Metrics 710
30.4 Case Study 1: Driveway Location 712
30.5 Case Study 2: Most Segments of a Traffic Impact Analysis 713
30.5.1 The Project Area and the Existing Condition 713
30.5.2 Proposed Use(s) of the Two Site(s) 715
30.5.3 Local Code & Local Ordinance Requirements 718
30.5.4 Other Given Conditions 718
30.5.5 Element 1: System Cycle 720
30.5.6 Element 2: The Developer’s Favorite Access Plan 720
30.5.7 Element 3: Existing Conditions, Capacity, and LOS Analyses 721
30.5.8 Element 4: Trip Generation 722
30.5.9 Element 5: Determine the Size of the Development, Trips Generated, and Internal Circulation 723
30.5.10 Element 6: Driveway Locations and Special Arterial and Intersection Design Features 723
30.5.11 Element 7: Mitigation Measures 723
30.5.12 Element 8: Final Report and Presentation 724
30.6 Summary 724
References 724
Problems 724
Index 726

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