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TRB’s Airport Cooperative Research Program (ACRP) Report 51: Risk Assessment Method to Support Modification of Airfield Separation Standards is intended to be used to support requests for modification of standards in those circumstances where the design criteria for separations between taxiways/taxilanes and other taxiways/taxilanes and fixed or movable objects as well as separations between taxiways and runways cannot be met.

The following appendices, included in the pdf and print version of the report, will be helpful in understanding the methodology.

  • Appendix A: Risk Assessment Methodology presents a methodology for five different types of circumstances: taxiway/taxilane to taxiway, taxiway to object, taxilane to taxilane, taxilane to an object, and runway to taxiway/taxilane or object;
  • Appendix F: Aircraft Database Summary presents a summary of aircraft characteristics by model; and
  • Appendix H: Analysis of MOS Cases summarizes information collected in the modification of standards survey and presents results of application of the methodology described in Appendix A to each modification of standards case.

Other report appendices, which are available online only, provide detail and information on the development of the methodology.

In addition, the project developed a

PowerPoint presentation

that may be useful for introducing and explaining the methodology to stakeholders.

In July 2021, an errata was posted for this publication: In Table 7 on page 25, the LDVO coefficient was changed from -3.088 to -13.088. The online version of the report has been corrected.

Suggested Citation

National Academies of Sciences, Engineering, and Medicine. 2011. Risk Assessment Method to Support Modification of Airfield Separation Standards. Washington, DC: The National Academies Press.

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Publication Info

136 pages |  8.5 x 11 |  Paperback
ISBN: 978-0-309-21332-5
Chapters skim
Front Matter i-vii
ACRP Report 51 Risk Assessment Method to Support Modification of Airfield Separation Standards 1-1
Transportation Research Board 2011 Executive Committee 2-2
Risk Assessment Method to Support Modification of Airfield Separation Standards 3-4
About the National Academies 5-5
ACRP Project 04-09 Panel 6-5
Author Acknowledgments 6-6
Foreword 7-7
Contents 8-9
Summary 10-10
Chapter 1 - Background 11-10
Introduction 11-10
Project Goals 11-10
Major Challenges Associated with Airfield Separations 11-11
FAA Modification of Standards 12-12
Chapter 2 - Airfield Separation Rationale 13-12
FAA Rationale 13-16
ICAO Rationale 17-20
Chapter 3 - Data for Modeling Aircraft Deviations 21-20
Airfield Lateral Deviation Studies 21-20
Veer-Off Accidents and Incidents 21-21
Aircraft Veer-Off Database Organization 22-22
Normal Operations Data (NOD) 23-23
Aircraft Data 24-24
Chapter 4 - Methodology Approach 25-24
Taxiway and Taxilane Deviation Modeling 25-29
Runway Deviation Modeling 30-36
Chapter 5 - Validating the Methodology 37-36
MOS Case Studies 37-36
MOS Survey 37-36
Methodology Applied to MOS Cases 37-39
Chapter 6 - Conclusions and Recommendations 40-39
Major Achievements 40-40
Limitations 41-40
Recommendations for Future Work 41-42
Glossary of Acronyms 43-44
Definitions 45-45
References 46-47
Appendix A - Risk Assessment Methodology 48-87
Appendix B - Collision Risk Model 88-88
Appendix C - Key Studies on Aircraft Deviation 89-89
Appendix D - List of Veer-Off Accidents and Incidents 90-90
Appendix E - Sample of Normal Operations Data 91-91
Appendix F - Aircraft Database Summary 92-100
Appendix G - Summary of FAA/Boeing Taxiway Deviation Studies 101-101
Appendix H - Analysis of MOS Cases 102-130
Abbreviations used without definitions in TRB publications 131-122

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