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Accident Reconstruction Science Fourth Edition - Lawyers & Judges Publishing Company, Inc.

Accident Reconstruction Science Fourth Edition

$ 99.00

  • Author: Alan Watts
  • ISBN 10: 1-936360-03-9
  • ISBN 13: 978-1-936360-03-1
  • Copyright Date Ed:  October 1, 2011
  • Pages: 416
  • Binding Information: Casebound
  • Size: 6 ✕ 9 Inches (US)

Written for the reconstructionist, attorney, automotive engineer, or other interested professional, this brand new edition examines the science of reconstructing and analyzing an automobile accident. Learn how to analyze accidents and judge speed from the final position of the vehicle. Also covered are topics such as sideswipe collisions, rollovers, calculations of collision timing and accelerations and measuring vehicle crush, among many others. Dr. Alan Watts explains basic concepts of physics, and then applies them to accident reconstruction. The text will be readily understood by any reader with a basic understanding of accident reconstruction; however, full details and equation derivations are provided for those with either higher technical education or a wish to more fully understand the issues.

Topics Include

  • General material loading responses
  • Vehicle crush response for impacts into rigid barriers
  • Crush responses in two-vehicle, low speed collisions
  • Computer modeling methods
  • Energetics of collisions
  • Bumper behavior
  • Integrated hits and other effects
  • Interesting mechanical models
  • Comparisons between the CRASH3 and the POD models
  • Proper solutions to various problems
  • Rollovers and side trips
  • Mounting and surviving
  • Specific examples and animations
  • Accident reconstruction definitions and other notes

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Table of Contents

Chapter 1: Introduction

1.1 Understanding the Physics

1.2 Accuracy

1.3 Terminology

1.4 A Matter of Perspective

Chapter 2: General Material Loading Responses

2.1 Energy and Force

2.2 Responses to Force

A. Elastic Response

B. Plastic Response

C. Viscoelastic Response

D. Brittle Response

2.3 Other Definitions

A. Stress

B. Strain

2.4 Sign Convention

Chapter 3: Vehicle Crush Response for Low-Speed Impacts into Rigid Barriers

3.1 The Bumper Response

3.2 Vehicle Crush Characteristics

3.3 The Difference between Input and Absorbed Energy

Chapter 4: Crush Responses in Two-Vehicle, Low-Speed Collisions

4.1 In-Line Collisions

4.2 Post-Impact Speeds

4.3 Coefficient of Restitution

4.4 Critical Damage Speed

4.5 Numerical Values of R and a

4.6 Contact Time

4.7 Distance Moved during Impact

4.8 Braking during Impact

4.9 The Engineer’s Box

4.10 Rule of Thumb: The “One-mph-per-Inch-Crush” Rule

4.11 Incomplete and Side Impacts

4.12 Partial or Sideswipe Impacts

4.13 Induced Rotations

4.14 Movie Theatrics

4.15 Payload Considerations

4.16 Sensitivity Analysis

Chapter 5: Computer Modeling Methods

5.1 Introduction

5.2 The CRASH3 Program

5.3 Multiple Hits on a Vehicle

5.4 Issues to Watch Out For

Chapter 6: Energetics of Collisions

6.1 The Energetics of a Collision

6.2 The Critical Speeds

6.3 Example: Two-Car Crash Effects

6.4 Relative Energy Absorption

Chapter 7: Bumper Behavior

7.1 Energy-Absorbing Bumpers

7.2 Sensitivity to Non-Linearity

7.3 Preload Effects and Isolator Friction

7.4 Isolator Aging

7.5 Viscous Behavior of Plastic Bumpers

7.6 Transmission of Bumper Force

7.7 Static versus Dynamic Isolator Forces

7.8 Bumper Stroking versus Delta-v: Restitution for Car-to-Car Impacts

Chapter 8: Integrated Hits and Other Effects

8.1 Absorbed Energy (Again) and the Multiple-Hit Logic

8.2 Front-to-Front versus Front-to-Rear Impacts

8.3 Bumper Speed Limits

8.4 Damage: Car-to-Car versus Car-to-Barrier

8.5 Bumper-to-Bumper versus Bumper-to-Soft-Bodywork

A. Case A: Bumper-to-Bumper

B. Case B: Bumper-to-Soft-Bodywork

C. Discussion

8.6 Aggressivity of Trucks and SUVs

Chapter 9: Interesting Mechanical Models

9.1 Internal Damage

9.2 Beam Bending

9.3 The Soda-Can Model

Chapter 10: Comparisons between the CRASH3 and the POD Models

10.1 The Values of R and a, and the CRASH3 Equivalents A and B

10.2 Updates for CRASH3 and SLAM

10.3 Occam’s Razor

10.4 Paths and Loci

Chapter 11: Proper Solutions to Various Problems

11.1 Solving the Equations

11.2 How Not to Solve a Problem

11.3 Experiments versus Theory: Balderdash, Dishonesty and Junk Science

11.4 Component Testing versus Systems Testing

11.5 Angular Momentum (AM)

A. Option A

B. Option B

C. Option C

11.6 Submarine Collision Logic

11.7 Special Cases

11.8 The Influence of Restitution on Multicar Impacts

Chapter 12: Rollovers and Side Trips

12.1 Background

12.2 Types of Rollover

A. Cornering Rollover (Turn)

1. Centripetal and centrifugal rotational effects

2. Tire forces and direction

3. True dynamics versus accident reconstruction

4. The roll

5. Rotation rate

6. Contact-point lift-off

7. Time of roll

8. Does the roll continue?

9. Sensitivity to unknowns in R and Krot

10. Conclusions for a simple turn roll

B. The Curb Impact Trip Condition

12.3 The Side Slide Case

Chapter 13: A Typical Mathcad Solution

13.1 Introduction

13.2 Code Output

Chapter 14: Side-Swipe Collisions

14.1 Introduction

14.2 Small-Angle Effects

14.3 The K Factors

Chapter 15: Measuring the Crush

15.1 Introduction

15.2 Measuring the Crush

Chapter 16: The Heavy Vehicle versus Light Vehicle Problem

16.1 Introduction

16.2 Can We Build a Lightweight Car and Maintain Safety?

16.3 Four Solutions

Chapter 17: Conservation of Linear Momentum

Chapter 18: Event Data Recorders (EDRs)

Chapter 19: Going Round the Bend: Critical Yaw Velocity and Steering Logic

19.1 Introduction

19.2 Steering Effects

19.3 Higher Speeds

19.4 Yawing, Understeer and Oversteer

19.5 The Yaw Critical Velocity

19.6 High Rate Cornering and Electronic Stability Control

19.7 Mathcad Plots

Appendix A: Accident Reconstruction Definitions and Other Notes

Customer Reviews

Based on 4 reviews
Science & Justice; 34(7)
Science & Justice; 34(7)

None of the recognized accident investigation texts deal adequately with low speed impacts but this book is a valiant attempt to rectify that omission. The authors are scientists and engineers who have set out to apply their practical physical experience, gained from studying the behavior of materials, to producing a solidly physics based text on vehicle dynamics and occupant kinematics. I think they have succeeded.

Joseph E. Badger
Law and Order

Low Speed Automobile Accidents was developed to provide reconstructionists, engineers, police, insurance adjusters and attorneys with the tools and understanding for correctly interpreting and reconstructing such (low-speed) collisions, and to more readily appreciate just when and how occupant injury can occur. Attorney Randall Kehl provides legal commentary on cases. A comprehensive appendix offers conversions, definitions, and newton's laws. It also explains conservation of linear momentum and torque, perception/reaction time, plus trips/flips, vaults, and roll-overs. A reconstructionist should have this book.

Book News, Inc.
Book News, Inc.

Previous edition of this text were titled Low Speed Automobile Accidents. Interestingly, the first edition (1996) was 270 pages, and the third edition (2003) grew to 870 pages. Watts is a consultant with several decades of experience in deciphering the physical and engineering aspects of crashes. He decided to change course with this fourth edition text by expanding coverage to all speed ranges. He notes in the preface that reconstruction is concerned with application of mathematical techniques to understand what happened, unlike investigation, which studies material evidence at the scene. Coverage encompasses general material loading responses, computer modeling methods, the energetics of collisions, and bumper behavior, among other topics.

Joseph E. Badger
First Contact, a newsletter of IATAI

Back in December 1996, I wrote about a book devoted to those dreaded low speed crashes. The book was the collaborative effort of three men: Alan Watts, Dale Atkinson and Corey Hennessy. Since then, the book has undergone upgrades (2nd Ed. 1999), an expansion, (3rd Ed. 2003), and now comes a revision, (4th Ed.): Accident Reconstruction Science. This time, just a single author whose impressive credentials read like a Whos Who of many people but it is about only one: Alan J. Watts, Ph.D. I do not want to merely suggest he is multitalented, but he authored or co-authored papers covering myriad topics from Spacecraft Microparticle Impact Flux Definition to "Optical Scatter due to Impact Effects to "Potential Impact Damage Effects for Short Mission Spacecraft in a Highly Elliptical Orbit. Whew! Moreover, Watts designed and developed a durable bremsstrahlung radiation converter/shield that survives high-energy impulsive loading on materials and structures for the PRONTO II test facility at Sandia National Laboratories in Albuquerque. (No, I didnt know what bremsstrahlung was either, but Ill save you from looking it up. It is electromagnetic radiation produced by the acceleration or especially the deceleration of a charged particle after passing through the electric and magnetic fields of a nucleus. Now, know any more than you did before? But I digress.) Watts designed & developed instrumentation and test fixtures while at Ktech (whose employees have comprehensive expertise in pulsed power engineering airborne flight test and satellite systems support and tracking research and development large facility operations, maintenance, and engineering) []. He was chief scientist at POD (Programs on Demand) in Albuquerque, NM, a private company categorized under Research Service, established in 1994 [] for thermomechanical response testing for underground nuclear response tests at the Nevada Test Site. I met Dr. Watts long ago (1999) in Room H-1073 on the campus of the University of North Florida at the 17th annual session of the Institute of Police Technology and Managements (IPTM) Special Problems in Traffic Accident Reconstruction in Jacksonville. His topic: Low Speed Collisions. One might say that the man has been around the block a couple of times when it comes to the subject at hand. If you want to check him out, do NOT Google Alan Watts. You will reach 1.5 million entries, none of which is our Alan James Watts, Ph.D. You need to go to Trust me. That site is whats called an expert witness directory. It lists his curriculum vitae and cites, via the Publications link, the title of his first book: Low Speed Automobile Accidents: Accident Reconstruction and Occupant Kinematics, Dynamics and Biomechanics. But about his new book Accident Reconstruction Science First, if you are a math nut, you will go feral and become totally engrossed around Chapter 4: Crush Responses in Two-Vehicle, Low-Speed Collisions. There are gobs more equations in Chapter 6: Energetics of Collisions. By Chapter 12, Rollovers and Side Trips, you will be ecstatic! Not to fear. If mathematical prowess is not your forte, you will still relish Watts treatment of such topics as Experiments versus Theory: Balderdash, Dishonesty and Junk Science (Chapter 11), Interesting Mechanical Models (Chapter 9), and Bumper Speed Limits (Chapter 8). However, I must admit that the text is chock-full o formulae. In addition, if algebra and trig make you squeamish, you might as well skip Chapter 16: The Heavy Vehicle versus Light Vehicle Problem. For example, there is an equation that commences on page 237, but I never quite figured out where it quits....around page 254, I think. However, there are some charts and graphs that Watts and Weintraub wedged in among those 17 or so pages. On page 327, Watts slipped in a short chapter (only two pages) on Event Data Recorders with nary a single equation, graph or chart. The author explains that he didnt dwell on EDR usage for the simple reason that the practice of reading data is precisely that: it is reading data, it is not the act of reconstructing an accident, although the data may be usefully compared with the results of a proper reconstruction. Although Watts is primarily into the biomechanical, he states: … we have renamed this fourth edition and have also removed the section on biomechanics and occupant responses. However, we retain all the biomechanical references to help those who wish to independently study the literature. In case you havent heard by now, Lawyers & Judges Publishing Co. produces legal books specializing in accident reconstruction and litigation, forensic economics, nursing home litigation, forensic science and more. If you go to their website (, you might see a blurb and link to Alan J. Watts book on the sites home page. You will see where the book was Written for the recon...

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