Highway Engineering

Martin Rogers, PhD, is a Transport Planning Practitioner and Senior Lecturer in the School of Transport and Civil Engineering, Technological University Dublin, Ireland. He is a Transport Planning Professional (TPS), a Chartered Civil Engineer (ICE) and Chartered Town Planner (RTPI), with extensive experience in both the private and public sectors, including membership in the Dublin Transport Initiative Study Team that devised the Dublin city region’s first integrated transportation plan. Bernard Enright, PhD, is a Lecturer in the School of Transport and Civil Engineering, Technological University Dublin, Ireland. He has considerable experience in the engineering and information technology industries and has published extensively on highway engineering and related subjects.

About the Companion Website xv

1 The Transportation Planning Process 1

1.1 Why Are Highways So Important? 1

1.2 The Administration of Highway Schemes 1

1.3 Sources of Funding 2

1.4 Highway Planning 3

1.4.1 Introduction 3

1.4.2 Travel Data 4

1.4.3 Highway Planning Strategies 6

1.4.3.1 Land-Use Transportation Approach 6

1.4.3.2 The Demand Management Approach 6

1.4.3.3 The Car-Centred Approach 7

1.4.3.4 The Public Transport-Centred Approach 7

1.4.4 Transportation Studies 7

1.4.4.1 Transportation Survey 7

1.4.4.2 Production and Use of Mathematical Models 8

1.5 The Decision-Making Process in Highway and Transport Planning 8

1.5.1 Introduction 8

1.5.2 Economic Assessment 10

1.5.3 Environmental Assessment 11

1.5.4 Public Consultation 12

1.6 Summary 13

References 13

2 Forecasting Future Traffic Flows 15

2.1 Basic Principles of Traffic Demand Analysis 15

2.2 Demand Modelling 16

2.3 Land-Use Models 18

2.4 Trip Generation 18

2.4.1 TRICS ® Database 23

2.5 Trip Distribution 24

2.5.1 Introduction 24

2.5.2 The Gravity Model 25

2.5.3 Growth Factor Models 30

2.5.4 The Furness Method 31

2.6 Modal Split 36

2.7 Traffic Assignment 41

2.8 A Full Example of the Four-Stage Transportation Modelling Process 46

2.8.1 Trip Production 46

2.8.2 Trip Distribution 47

2.8.3 Modal Split 50

2.8.4 Trip Assignment 52

2.9 ‘Decide and Provide’ Versus ‘Predict and Provide’ 53

2.10 Concluding Comments 54

Additional Problems 54

References 57

3 Scheme Appraisal for Highway Projects 59

3.1 Introduction 59

3.2 Economic Appraisal of Highway Schemes 60

3.3 Cba 61

3.3.1 Introduction 61

3.3.2 Identifying the Main Project Options 61

3.3.3 Identifying all Relevant Costs and Benefits 62

3.3.3.1 Reductions in VOCs 63

3.3.3.2 Savings in Time 63

3.3.3.3 Reduction in the Frequency of Accidents 64

3.3.4 Economic Life, Residual Value, and the Discount Rate 64

3.3.5 Use of Economic Indicators to Assess Basic Economic Viability 65

3.3.6 Highway CBA Worked Example 67

3.3.6.1 Introduction 67

3.3.6.2 Computation of Discounted Benefits and Costs 68

3.3.6.3 Npv 70

3.3.6.4 Benefit-Cost Ratio 70

3.3.6.5 Irr 70

3.3.6.6 Summary 70

3.3.7 Coba 70

3.3.8 Advantages and Disadvantages of CBA 71

3.4 Payback Analysis 73

3.5 Environmental Appraisal of Highway Schemes 75

3.6 The New Approach to Appraisal 80

3.6.1 Environment 81

3.6.1.1 Noise 81

3.6.1.2 Local Air Quality 81

3.6.1.3 Landscape 82

3.6.1.4 Biodiversity 82

3.6.1.5 Heritage 82

3.6.1.6 Water 82

3.6.1.7 Safety 83

3.6.1.8 Economy 83

3.6.1.9 Journey Times and VOCs 83

3.6.1.10 Costs 83

3.6.1.11 Reliability 83

3.6.1.12 Regeneration 83

3.6.1.13 Accessibility 84

3.6.1.14 Pedestrians, Cyclists, and Equestrians 84

3.6.1.15 Access to Public Transport 85

3.6.1.16 Community Severance 85

3.6.1.17 Integration 85

3.7 NATA Refresh 86

3.7.1 Changes to the AST 86

3.7.2 Enhanced Presentation of Monetary Impacts 87

3.7.3 More Detailed Relationship Between Benefit-Cost Ratio and Value for Money 87

3.8 Transport Analysis Guidance: The Transport Appraisal Process 87

3.9 Project Management Guidelines 89

3.10 Common Appraisal Framework for Transport Projects and Programmes 90

3.11 Summary 91

References 91

4 Basic Elements of Highway Traffic Analysis 93

4.1 Introduction 93

4.2 Surveying Road Traffic 93

4.2.1 Introduction 93

4.2.2 Vehicle Surveys 94

4.2.2.1 Introduction 94

4.2.2.2 Manual Counts 94

4.2.2.3 Automatic Counts 94

4.2.3 Speed Surveys 95

4.2.4 Delay/Queuing Surveys 96

4.2.5 Area-Wide Surveys 96

4.2.5.1 Introduction 96

4.2.5.2 Roadside Interview Surveys 97

4.2.5.3 Self-Completion Forms 97

4.2.5.4 Registration Plate Surveys 97

4.3 Journey Speed and Travel Time Surveys 98

4.3.1 Introduction 98

4.3.2 The Moving Observer Method 98

4.4 Speed, Flow, and Density of a Stream of Traffic 103

4.4.1 Speed–Density Relationship 103

4.4.2 Flow–Density Relationship 104

4.4.3 Speed–Flow Relationship 105

4.5 Headway Distributions in Highway Traffic Flow 109

4.5.1 Introduction 109

4.5.2 Negative Exponential Headway Distribution 110

4.5.3 Limitations of the Poisson System for Modelling Headway 114

4.6 Queuing Analysis 114

4.6.1 Introduction 114

4.6.2 The D/D/1 Queuing Model 114

4.6.3 The M/D/1 Queuing Model 118

4.6.4 The M/M/1 Queuing Model 119

4.6.5 The M/M/N Queuing Model 120

Additional Problems 123

References 128

5 Determining the Capacity of a Highway 129

5.1 Introduction 129

5.2 The ‘Level of Service’ Approach Using the Transportation Research Board 129

5.2.1 Introduction 129

5.2.2 Some Definitions 131

5.2.3 Maximum Service Flow Rates for Multilane Highways 131

5.2.4 Maximum Service Flow Rates for Two-Lane Highways 137

5.2.5 Sizing a Road Using the Highway Capacity Manual Approach 140

5.3 The 2010 Highway Capacity Manual – Analysis of Capacity and Level of Service for Multi-Lane and Two-Lane Highways 143

5.3.1 Introduction 143

5.3.2 Capacity and Level of Service of Multilane Highways (2010 Highway Capacity Manual) 143

5.3.2.1 Flow Characteristics Under Base Conditions 143

5.3.2.2 Capacity of Multilane Highway Segments 144

5.3.2.3 Level of Service (LOS) for Multilane Highway Segments 144

5.3.2.4 Required Data for the LOS Computation 144

5.3.2.5 Computing LOS for a Multilane Highway 145

5.3.3 Capacity and Level of Service of Two-Lane Highways 150

5.3.3.1 Flow Characteristics Under Base Conditions 150

5.3.3.2 Capacity and Level of Service 150

5.3.3.3 Required Input Data and Default Values 151

5.3.3.4 Demand Volumes and Flow Rates 152

5.3.3.5 Computing LOS and Capacity for a Two-Lane Highway 152

5.3.3.6 Determining Level of Service for Class 1 Two-Lane Highways 154

5.3.3.7 Determining the Level of Service for Class 2 Two-Lane Highways 161

5.3.3.8 Determining the Level of service for Class 3 Two-Lane Highways 166

5.4 The 2016 Highway Capacity Manual – Analysis of Capacity and Level of Service for Multi-Lane Highways 167

5.4.1 Introduction 167

5.4.2 Capacity and Level of Service of Multilane Highways (2016 Highway Capacity Manual) 167

5.4.2.1 Speed Versus Flow 167

5.4.2.2 Baseline Conditions and Capacity 167

5.4.2.3 Determining Free-Flow Speed 168

5.4.2.4 Determination of Incident Flow Rate 168

5.4.2.5 Calculation of Density and Determination of Level of Service 168

5.5 The UK Approach for Rural Roads 170

5.5.1 Introduction 170

5.5.2 Estimation of AADT for a Rural Road in Its Year of Opening 171

5.6 The UK Approach to Urban Roads 173

5.6.1 Introduction 173

5.6.2 Forecast Flows on Urban Roads 174

5.7 Expansion of 12- and 16-Hour Traffic Counts into AADT Flows 177

5.8 Concluding Comments 178

Additional Problems 179

References 181

6 The Design of Highway Intersections 183

6.1 Introduction 183

6.2 Deriving DRFs from Baseline Traffic Figures 184

6.2.1 Existing Junctions 184

6.2.2 New Junctions 184

6.2.3 Short-Term Variations in Flow 184

6.2.4 Conversion of AADT to Highest Hourly Flows 185

6.3 Major/Minor Priority Intersections 185

6.3.1 Introduction 185

6.3.2 Equations for Determining Capacities and Delays 189

6.3.3 Geometric Layout Details 196

6.3.3.1 Horizontal Alignment 196

6.3.3.2 Vertical Alignment 196

6.3.3.3 Visibility 196

6.3.3.4 Dedicated Lane on the Major Road for Right-Turning Vehicles 196

6.4 Roundabout Intersections 197

6.4.1 Introduction 197

6.4.2 Types of a Roundabout 199

6.4.2.1 Mini-Roundabout 199

6.4.2.2 Normal Roundabout 200

6.4.2.3 Double Roundabout 200

6.4.2.4 Other Forms 201

6.4.3 Traffic Capacity at Roundabouts 203

6.4.3.1 Drf 205

6.4.4 Geometric Details 209

6.4.4.1 Entry Width 209

6.4.4.2 Entry Angle 209

6.4.4.3 Entry Radius 209

6.4.4.4 Entry Deflection/Entry Path Radius 210

6.4.4.5 Icd 210

6.4.4.6 Circulatory Carriageway 210

6.4.4.7 Main Central Island 210

6.5 Basics of Traffic Signal Control: Optimisation and Delays 210

6.5.1 Introduction 210

6.5.2 Phasing at a Signalised Intersection 212

6.5.3 Saturation Flow 212

6.5.4 Effective Green Time 217

6.5.5 Optimum Cycle Time 217

6.5.6 Average Vehicle Delays at the Approach to a Signalised Intersection 220

6.5.7 Average Queue Lengths at the Approach to a Signalised Intersection 222

6.5.8 Signal Linkage 223

6.6 Concluding Remarks 228

Additional Problems 228

References 230

7 Geometric Alignment and Design 233

7.1 Basic Physical Elements of a Highway 233

7.1.1 Main Carriageway 233

7.1.2 Central Reservation 233

7.1.3 Hard Shoulders/Hard Strips/Verges 234

7.2 Design Speed and Stopping and Overtaking Sight Distances 237

7.2.1 Introduction 237

7.2.2 Urban Roads 238

7.2.3 Rural Roads 239

7.2.3.1 Statutory Constraint 239

7.2.3.2 Layout Constraint 239

7.2.3.3 Alignment Constraint 240

7.2.3.4 New/Upgraded Rural Roads 242

7.3 Geometric Parameters Dependent on Design Speed 244

7.4 Sight Distances 244

7.4.1 Introduction 244

7.4.2 Stopping Sight Distance 245

7.4.3 Overtaking Sight Distance 246

7.5 Horizontal Alignment 248

7.5.1 General 248

7.5.2 Deriving the Minimum Radius Equation 248

7.5.3 Horizontal Curves and Sight Distances 251

7.5.3.1 Alternative Method for Computing Ms 253

7.5.4 Transitions 254

7.5.4.1 Shift 255

7.6 Vertical Alignment 258

7.6.1 General 258

7.6.2 K Values 259

7.6.3 Visibility and Comfort Criteria 260

7.6.4 Parabolic Formula 260

7.6.5 Crossfalls 263

7.6.6 Vertical Crest Curve Design and Sight Distance Requirements 264

7.6.6.1 Derivation of Crest Curve Formulae 265

7.6.7 Vertical Sag Curve Design and Sight Distance Requirements 269

7.6.7.1 Driver Comfort 269

7.6.7.2 Clearance from Structures 269

7.6.7.3 Sag Curves in Night-Time Conditions 270

Additional Problems 271

References 274

8 Highway Pavement Materials 275

8.1 Introduction 275

8.2 Pavement Components: Terminology 275

8.3 Soils at Subformation Level 279

8.4 Materials in Foundations 279

8.5 Materials in Flexible Pavements 280

8.5.1 Bitumen 280

8.5.2 Asphalt Concrete (Coated Macadams) 281

8.5.3 Hot Rolled Asphalt 282

8.5.4 Aggregates 282

8.5.5 Designation of Asphalt Materials Used in Flexible Pavements 282

8.6 Concrete in Rigid Pavements 284

8.7 Surfacing Materials 285

8.7.1 Surface Dressing and Modified Binders 285

8.7.1.1 Cutback Bitumen 285

8.7.1.2 Bituminous Emulsions 285

8.7.1.3 Chippings 286

8.8 Stiffness Modulus 286

8.9 Measurement and Testing of Material and Pavement Properties 289

8.9.1 CBR Test 289

8.9.2 Determination of CBR Using Plasticity Index 292

8.9.2.1 Liquid Limit 292

8.9.2.2 Plastic Limit 292

8.9.2.3 Plasticity Index 292

8.9.2.4 Using I P and Soil Type to Derive CBR 292

8.9.3 Using CBR to Estimate Stiffness Modulus 293

8.9.4 Falling Weight Deflectometer (FWD) 293

8.9.5 Light Weight Deflectometer (LWD) 297

8.9.6 Dynamic Cone Penetrometer (DCP) 298

8.9.7 Penetration Test for Bitumen 298

8.9.8 Softening Point of Bitumen 299

8.9.9 Polished Stone Value (PSV) 300

8.9.10 Aggregate Abrasion Value (AAV) 300

8.9.11 Patch Test 300

Additional Problems 301

References 302

Design Manual for Roads and Bridges 302

Standards 302

Other Government Publications 303

Other References 303

9 Design and Construction of Highway Pavements 305

9.1 Introduction and Design Approach 305

9.2 Sustainability and Good Road Design 306

9.3 Whole-Life Cost Analysis 307

9.4 Traffic Loading 307

9.4.1.1 Commercial Vehicle Flow (F) 309

9.4.1.2 Growth Factor (G) 309

9.4.1.3 Wear Factor (W) 310

9.4.1.4 Design Period (Y) 310

9.4.1.5 Percentage of Vehicles in the Heaviest Loaded Lane (P) 311

9.5 Foundation Design 314

9.5.1 Introduction 314

9.5.2 Restricted Foundation Design Method 316

9.5.3 Performance Design Method 319

9.5.3.1 Design Charts for Foundation Layer Thickness: Performance Design 321

9.5.3.2 Testing Foundation Surface Modulus on Demonstration Area and During Construction 322

9.5.4 Drainage and Frost 323

9.6 Pavement Design 324

9.6.1 Design of Flexible Pavements 325

9.6.2 Design of Rigid Pavements 328

9.6.2.1 Continuously Reinforced Concrete 328

9.6.2.2 Roller Compacted Concrete 331

9.6.2.3 Jointed Concrete Pavements 332

9.7 Construction of Flexible Pavements 334

9.7.1 Construction of Bituminous Road Surfacings 334

9.7.1.1 Transporting and Placing 335

9.7.1.2 Compaction of the Bituminous mix 336

9.7.1.3 Application of Coated Chippings to Smooth Surfacings 336

9.8 Construction of Rigid Pavements 336

9.8.1 Concrete Slab and Joint Details 336

9.8.1.1 Joints in Concrete Pavements 337

9.8.2 Reinforcement 339

Additional Problems 339

References 340

Design Manual for Roads and Bridges 340

Standards 341

Other Government Publications 341

Other References 342

10 Pavement Maintenance 343

10.1 Introduction 343

10.2 Pavement Deterioration 343

10.3 Compiling Information on the Pavement’s Condition 345

10.3.1 Introduction 345

10.3.2 Traffic-Speed Surveys of Surface and Structural Condition 346

10.3.3 Traffic-Speed Surveys of Skidding Resistance 348

10.3.3.1 Skidding Resistance 348

10.3.3.2 Measurement of Skidding Resistance 349

10.3.4 Visual Condition Surveys 350

10.3.5 Cores 351

10.3.6 Dynamic Cone Penetrometer 351

10.3.7 Deflectograph 351

10.3.8 Ground-Penetrating Radar (GPR) 353

10.3.9 Falling Weight Deflectometer (FWD) 354

10.3.10 Other Investigation Techniques 354

10.4 Forms of Maintenance 354

10.4.1 Flexible Pavements 355

10.4.2 Rigid Pavements 357

References 359

11 The Highway Engineer and the Development Process 361

11.1 Introduction 361

11.2 Transport Assessments 362

11.2.1 Introduction 362

11.2.2 Identifying the Need for an Assessment 362

11.2.3 Preparing a TA 363

11.2.3.1 Description of On-Site Existing Baseline Conditions 364

11.2.3.2 Definition of the Proposed Development 365

11.2.3.3 Setting the Assessment Years for Which Capacity Analyses Are Carried Out 365

11.2.3.4 Setting the Analysis Periods for Which Capacity Analyses Are Carried Out 365

11.2.3.5 Estimation of Trips Generated by the Proposal 366

11.2.4 Final Comment 367

11.3 Travel Plans 367

11.3.1 Introduction 367

11.3.2 Thresholds 367

11.3.3 When Is a Travel Plan Required? 368

11.3.4 What Information Should Be Included Within a Travel Plan? 369

11.3.4.1 Appointment of a Travel Plan Coordinator 369

11.3.4.2 Initial Monitoring Process 369

11.3.4.3 Setting Targets for Modal Split 370

11.3.4.4 Monitoring How Things Have Changed 370

11.3.5 Mobility Management Plans in Ireland 371

11.4 Road Safety Audits 372

11.4.1 Principles Underlying the Road Safety Audit Process 372

11.4.2 Definition of Road Safety Audit 373

11.4.3 Stages Within Road Safety Audits 374

11.4.4 Road Safety Audit Response Report 375

11.4.5 Checklists for Use Within the RSA Process 376

11.4.6 Risk Analysis 378

11.4.7 Conclusions 381

References 381

12 Defining Sustainability in Transportation Engineering 383

12.1 Introduction 383

12.2 Social Sustainability 383

12.3 Environmental Sustainability 383

12.4 Economic Sustainability 384

12.5 The Four Pillars of Sustainable Transport Planning 384

12.5.1 Put Appropriate Governance in Place 385

12.5.2 Provide Efficient Long-Term Finance 385

12.5.3 Make Strategic Investments in Major Infrastructure 385

12.5.4 Support Investments Through Local Design 386

12.5.5 Concluding Comments 386

12.6 How Will Urban Areas Adapt to the Need for Increased Sustainability? 386

12.7 The Role of the Street in Sustainable Transport Planning 387

12.7.1 Street Classification System 387

12.7.2 Designing an Individual Street 387

12.7.2.1 Introduction 387

12.7.2.2 A Rational Approach to Speed in Urban Areas 389

12.7.3 The Pedestrian Environment 390

12.7.3.1 General Design Principles of Footpaths 390

12.7.4 Design for Cycling 392

12.7.4.1 Cycling Design Criteria 392

12.7.4.2 Design Guidelines 393

12.7.5 Carriageway Widths on Urban Roads and Streets 396

12.7.6 Surfaces 396

12.7.7 Junction Design in an Urban Setting 398

12.7.8 Forward Visibility/Visibility Splays 399

12.8 Public Transport 400

12.8.1 Bus and Rail Services in Cities 400

12.8.2 Design of Street Network to Accommodate Bus Services 401

12.9 Using Performance Indicators to Ensure a More Balanced Transport Policy 402

12.9.1 The Traditional Approach 402

12.9.2 Using LOS to Measure the Quality of Pedestrian Facilities 402

12.9.2.1 Introduction 402

12.9.2.2 Formulae for Estimation of Link-Based Pedestrian LOS 404

12.9.2.3 Free-Flow Walking Speed 405

12.9.2.4 Average Pedestrian Space 405

12.9.2.5 Pedestrian LOS Score (I p, link) 405

12.9.2.6 Determining Link-Based Pedestrian LOS 406

12.9.3 Using LOS to Measure the Quality of Cycling Facilities 408

12.9.3.1 Formulae for Estimation of Link-Based Bicycle LOS 408

12.9.3.2 Determining Link-Based Bicycle LOS 410

12.9.4 Measuring the Quality of Public Transport Using LOS 412

12.9.4.1 Acceleration-Deceleration Delay 414

12.9.4.2 Delay Due to Serving Passengers 414

12.9.4.3 Re-entry Delay (d re) 414

12.10 A Sustainable Parking Policy 419

12.10.1 Introduction 419

12.10.2 Seminal Work of Donald Shoup in the United States 419

12.10.3 The Pioneering ABC Location Policy in the Netherlands 420

12.10.4 Possible Future Sustainable Parking Strategies 421

References 422

Index 423