Fundamentals of Road Design

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Fundamentals of Road Design

W. KühnGermany

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W. KühnGermany

Acknowledgements

I would like to take this opportunity of thanking my student helpers, who were involved in preparing the figures and tables in this book to a significant degree. Thanks also go to the secretaries, who were involved in text editing. Last but not least, I would like to thank David Strauss who supported the process of translating the book into English. Special thanks go to my wife, Heike Kühn, who often had to spend her free time alone while work was progressing on the book. As a result, I would like to dedicate the book to her.

About the Author

Wolfgang Kühn studied transportation engineering at the “Friedrich List” University of Transportation and Traffic Sciences (HfV) in Dresden and completed his degree as a “Diplomingenieur” (graduate engineer) in 1977. After obtaining a qualification to teach at a university, he obtained his doctorate (Dr.-Ing) in 1981. He was a design engineer, estimator and construction manager at various planning offices and construction companies at different levels during the period 1981 – 1990. He founded the DELTA-PLAN GmbH planning office in 1990 and he has been successfully managing

this as the senior partner for 22 years. He completed his university teaching qualification by obtaining his Dr.-Ing. Habilitatus degree at the Technical University of Dresden in 2002. He was university professor at the University of Leipzig from 2004 until 2008 and he has been professor at the Institute of Transportation Systems Engineering at the University of Applied Sciences Zwickau since 1 March 2008.

During his many years of research work in the field of road design, he has produced 4 dissertations, 70 publications in professional journals and given 98 lectures at specialist conferences. He has also provided support for a number of students writing their degree dissertations or taking their master’s degree or doctoral theses. He has played a significant role in further developing the body of rules and regulations as head of the “Visualization” working group and a member of the “Designing new roads” working group at the German Road and Transportation Research Association (FGSV). He was awarded

the Friedrich List Prize in 2002 for his academic achievements in the field of developing new kinds of models and procedures for road design. Due to his institutional activities in transportation research he was appointed members of both the Geometric Design Committee and the Visualization in Transportation Committee of the TRB (Transportation Research Board). In 2011 Wolfgang received an outstanding paper award at the 4th International Geometric Design Symposium in Valencia (Spain).

Contents 

Preface ............................................................................................................................. xv

Chapter 1 Introduction ................................................................................................. 1

1.1 Overview ................................................................................................................. 1 1.2 General Matters ....................................................................................................... 1 1.3 Subdisciplines ......................................................................................................... 4

1.3.1 Road planning ................................................................................................. 4 1.3.2 Road design .................................................................................................... 4 1.3.3 Road building .................................................................................................. 4 1.3.4 Road operations .............................................................................................. 4

1.4 Rules and Regulations ............................................................................................. 5 1.5 Historical Developments ......................................................................................... 5

1.5.1 Introduction ..................................................................................................... 5 1.5.2 Antiquity ......................................................................................................... 5 1.5.3 The Middle Ages ............................................................................................. 6 1.5.4 The modern era ............................................................................................... 7

1.6 Questions ................................................................................................................. 7

Chapter 2 Classification and Standardization ............................................................ 9

2.1 Classes of Roads ..................................................................................................... 9 2.2 Road Categorization .............................................................................................. 10

2.2.1 Function of the road ...................................................................................... 10 2.2.2 Category groups ............................................................................................. 11 2.2.3 Connecting function level ............................................................................. 12 2.2.4 Road category ............................................................................................... 13

2.3 Questions ............................................................................................................... 20

Chapter 3 Driver – Vehicle – Road Interaction ........................................................ 21

3.1 Driving Area .......................................................................................................... 21 3.2 Absorbing Information .......................................................................................... 22

3.2.1 Basic assumptions ......................................................................................... 22 3.2.2 Properties of the human eye .......................................................................... 22 3.2.3 Classification of the driving area .................................................................. 24 3.2.4 Visual behavior ............................................................................................. 26 3.2.5 Proprioception ............................................................................................... 27

3.3 Drivers’ Ability to React ....................................................................................... 28

3.4 Questions ............................................................................................................... 29

Chapter 4 Vehicle Kinematics and Dynamics ........................................................... 31

4.1 Introduction ........................................................................................................... 31 4.2 Vehicle Kinematics ................................................................................................ 32

4.2.1 Equations of motion ...................................................................................... 32 4.2.2 Braking path .................................................................................................. 39

4.3 Vehicle Dynamics .................................................................................................. 45 4.3.1 Driving resistance ......................................................................................... 45 4.3.2 Vehicle-road adhesion ................................................................................... 48 4.3.3 Vehicle motion .............................................................................................. 51 4.3.4 Cornering ...................................................................................................... 51

4.4 Questions ............................................................................................................... 57

Chapter 5 Speed Terminology .................................................................................... 59

5.1 Overview ............................................................................................................... 59 5.2 Design Speed ve ..................................................................................................... 59 5.3 Speed v85 ............................................................................................................... 60 5.4 Average Assessment Speed vB ............................................................................... 65 5.5 Actual Cruising Speed vR....................................................................................... 65 5.6 Intersection Speed vK ............................................................................................. 65 5.7 Questions ............................................................................................................... 67

Chapter 6 Sight Distances ........................................................................................... 69

6.1 Principles ............................................................................................................... 69 6.2 Meteorological Sight Distance .............................................................................. 69 6.3 Physiological and Psychological Perception of Sight Distance ............................. 69 6.4 Geometrical Sight Distances ................................................................................. 70

6.4.1 Overview ....................................................................................................... 70 6.4.2 Stopping sight distance ................................................................................. 70 6.4.3 Passing sight distance ................................................................................... 72

6.5 Existing Sight Distances ........................................................................................ 77 6.6 Questions ............................................................................................................... 78

Chapter 7 Alignment ................................................................................................... 79

7.1 Principles ............................................................................................................... 79 7.2 Design Elements on the Horizontal Projection ...................................................... 80

7.2.1 Review .......................................................................................................... 80 7.2.2 Straights ........................................................................................................ 81 7.2.3 Circular arcs principles ................................................................................. 82 7.2.4 Transition curve principles ............................................................................ 85 7.2.5 The clothoid as a standard transition curve ................................................... 88 7.2.6 Horizontal alignment curves ......................................................................... 92 7.2.7 Combined curves .......................................................................................... 93 7.2.8 Apex clothoids .............................................................................................. 97 7.2.9 Inflection lines principles .............................................................................. 99 7.2.10 Egg-shaped line principles ........................................................................ 103 7.2.11 Calculation examples (Weise, Kühn, et al., 1980) ..................................... 105

7.3 Design Elements on the Vertical Projection ......................................................... 119

7.3.1 General issues .............................................................................................. 119 7.3.2 Gradients on roads ...................................................................................... 122 7.3.3 Quadratic parabolas .................................................................................... 124 7.3.4 Example: calculations on the vertical projection (Weise, Kuhn, et al., 1980) ......................................................................... 128

7.4 Three-Dimensional Alignment ............................................................................ 130 7.4.1 General issues ............................................................................................. 130 7.4.2 Rules, guidelines, and criteria ..................................................................... 131 7.4.3 Checking methodology using quantitative parameters and qualitative criteria ....................................................................................... 132 7.4.4 Checking procedures ................................................................................... 147 7.4.5 Example ...................................................................................................... 150

7.5 Questions ............................................................................................................. 157

Chapter 8 Cross Section ............................................................................................ 159

8.1 Constituent Parts ................................................................................................. 159 8.2 Terms ................................................................................................................... 159 8.3 Determining Factors and Principles .................................................................... 161 8.4 Elements .............................................................................................................. 161 8.5 Standard Cross Sections ...................................................................................... 163 8.6 Selecting a Standard Cross Section ..................................................................... 165

8.6.1 Working stages ............................................................................................ 165 8.6.2 Example ...................................................................................................... 167

8.7 Footpaths and Cycle Paths .................................................................................. 176 8.8 Shoulders ............................................................................................................. 178 8.9 Developing the Cross Section ............................................................................. 179 8.10 Camber of Cross Section Elements ................................................................... 181

8.10.1 General matters ......................................................................................... 181 8.10.2 Camber in straights ................................................................................... 181 8.10.3 Camber in circular arcs ............................................................................. 182

8.11 Diagonal Gradient ............................................................................................. 183 8.12 Raised and Lowered Edges of Roads and Torsion............................................. 184

8.12.1 Summary ................................................................................................... 184 8.13 Questions ........................................................................................................... 190

Chapter 9 Intersections ............................................................................................. 191

9.1 Principles ............................................................................................................. 191 9.2 Traffic Procedures and Conflict Points ................................................................ 193 9.3 Speeds at Intersections ........................................................................................ 195 9.4 Intersection Intervals ........................................................................................... 196 9.5 At-Grade Intersections ......................................................................................... 196

9.5.1 Basic forms ................................................................................................. 196 9.5.2 Small roundabouts ...................................................................................... 199

9.6 Graded Interchanges ............................................................................................ 200 9.6.1 Planning principles ..................................................................................... 200 9.6.2 Linking ramps ............................................................................................. 202 9.6.3 Intersection areas ........................................................................................ 202 9.6.4 Intersection solutions .................................................................................. 203

9.7 Questions ............................................................................................................. 210

Chapter 10 Road Design Procedures ....................................................................... 211

10.1 Basic Principles .................................................................................................. 211 10.2 Process .............................................................................................................. 212

10.2.1 The area under examination ...................................................................... 212 10.2.2 The area of little conflict ........................................................................... 212 10.2.3 Examining options .................................................................................... 214 10.2.4 Route design methods ............................................................................... 215 10.2.5 Preliminary graphical draft with a flexible rod ......................................... 217 10.2.6 Comparing options .................................................................................... 226

10.3 Questions ........................................................................................................... 230

Chapter 11 Visualization ........................................................................................... 231

11.1 Theoretical Principles ........................................................................................ 231 11.1.1 Preface ...................................................................................................... 231

11.2 Perspective ........................................................................................................ 231 11.2.1 Definition .................................................................................................. 231 11.2.2 Central perspective .................................................................................... 232 11.2.3 Model assumptions.................................................................................... 233 11.2.4 Degree of detail ......................................................................................... 235

11.3 Computer Visualization ..................................................................................... 237 11.3.1 Process ...................................................................................................... 237 11.3.2 Kinds of images ........................................................................................ 238

11.4 Visualization Techniques ................................................................................... 241 11.4.1 Introduction ............................................................................................... 241 11.4.2 Amount of data .......................................................................................... 242

11.5 Development Stages .......................................................................................... 243 11.5.1 Freehand sketches ..................................................................................... 243 11.5.2 Physical models ........................................................................................ 243 11.5.3 Manually generated perspective images.................................................... 244 11.5.4 Computer-generated perspective images ................................................... 244 11.5.5 Animations ................................................................................................ 244 11.5.6 Real-time visualization ............................................................................. 245

11.6 Fields of Application ......................................................................................... 245 11.6.1 Review ...................................................................................................... 245 11.6.2 Project presentation ................................................................................... 246 11.6.3 Approval procedures ................................................................................. 246 11.6.4 Design checks ........................................................................................... 247 11.6.5 Results ....................................................................................................... 254

11.7 Immersive Images ............................................................................................. 255 11.8 Software Systems .............................................................................................. 258

11.8.1 Review ...................................................................................................... 258 11.8.2 Add-ons to standard CAD programs ......................................................... 258 11.8.3 Road design programs with a visualization module .................................. 260 11.8.4 Separate visualization programs ................................................................ 260

11.9 Questions ........................................................................................................... 261

Chapter 12 New Types of Model Projections .......................................................... 263

12.1 Preliminary Remarks ......................................................................................... 263 12.2 The Mathematical Model of the Flexible Rod Line .......................................... 263

12.2.1 Problems ................................................................................................... 263

12.2.2 Polynomial interpolation ........................................................................... 264 12.2.3 Spline interpolation ................................................................................... 267 12.2.4 Generalized spline functions ..................................................................... 280 12.2.5 Conclusions ............................................................................................... 288

12.3 Parameters for the route characteristic .............................................................. 289 12.3.1 Preliminary remarks .................................................................................. 289 12.3.2 Curvature, bendiness and parameters derived from this ........................... 289 12.3.3 Bendiness and parameters derived from this ............................................. 291 12.3.4 Specific route parameters (SP) .................................................................. 292 12.3.5 Fluidity criterion (FL) ............................................................................... 292 12.3.6 Curves with similar radii ........................................................................... 292 12.3.7 Results of experiments .............................................................................. 293

12.4 “DITRA” Dialogue Routing Program System .................................................. 293 12.4.1 Preliminary remarks .................................................................................. 293 12.4.2 Model projection ....................................................................................... 294 12.4.3 Curvature graph ........................................................................................ 298 12.4.4 Explanations of the design methodology .................................................. 300 12.4.5 Example .................................................................................................... 305 12.4.6 Summary and conclusions ........................................................................ 307

12.5 Three-Dimensional Design Approach ............................................................... 308 12.5.1 The problem .............................................................................................. 308 12.5.2 Review of developments ........................................................................... 308 12.5.3 Mathematical model projections ................................................................ 311 12.5.4 Axis calculation with three-dimensional elements .................................... 313 12.5.5 Summary and conclusions ........................................................................ 318

12.6 Questions ........................................................................................................... 320

References ..................................................................................................................... 321

Preface

This reference book developed as a result of Professor Dr Kühn’s teaching at the Universities of Leipzig, Magdeburg and Zwickau, his long-standing practical work as a design engineer at various planning offices and his detailed research work in the German Road and Transportation Research Association (FGSV) and international working groups.

This reference book communicates the basic theoretical knowledge and the practical requirements and experience for designing, mapping, calculating and checking roads and the planning process overall – and at the same time reveals important development trends.

The reference book is guided by the current rules and regulations in Germany, it universalizes this knowledge and also integrates important current research results in road design processes.

In order to restrict the scope of the book, it only deals with the theoretical principles and knowledge and the practical experience for designing rural roads, i.e. the special features of urban roads are not mentioned here. This clear separation primarily results from the different principles and rules and regulations.

The terms, definitions, abbreviations and formula symbols are based on German usage, but can be transferred to an international framework without any difficulties.

The work is particularly designed to be a course book for students of road design. As a reference book, it supports the ongoing training process for road transportation engineers in planning offices and public bodies. Any specialist working in the transportation sector can use it as a reference book.

Wolfgang Kühn, 2013