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.

• Appendix B: Collision Risk Model
• Appendix C: Key Studies on Aircraft Deviation
• Appendix D: List of Veer-Off Accidents and Incidents
• Appendix E: Sample of Normal Operations Data
• Appendix G: Summary of FAA/Boeing Taxiway Deviation Studies

In addition, the project developed a PowerPoint presentation that may be useful for introducing and explaining the methodology to stakeholders.