CHAPTER 2 Research Approach

The research objective was accomplished using seven tasks broken into two phases. These tasks defined a comprehensive and logical framework for conducting the research.

Phase I

Task 1. Review the NCHRP Project 20-07/417 final report, ADM, HDG, and all related information

Review of NCHRP 20-07/417 Results

The results and conclusions from NCHRP 20-07/417 were revisited and discussed with the NCHRP 24-50 Panel. This review included going through margin comments made in the 2014 ADM Word file, and subsequent comments provided by the TCHH.

Critical Literature Review of other Relevant Information

A critical literature review was completed to identify new topics that should be included beyond what was identified in NCHRP 20-07/417. The literature review concentrated on new information and technology not addressed in the 2014 ADM. In general, the information in the ADM (policy, criteria, and design standards) was considered relevant and up to date as of the 2014 publication date, so the literature review focused on information published since 2014. New chapters identified in NCHRP 20-07/417 (Stormwater Best Management Practices (BMP), Aquatic Organism Passage (AOP) and Resilience) required correspondingly more effort in the literature review.

Survey of State Transportation Agencies

Task 1 also included a survey of state transportation agencies to identify perceived weaknesses in the 2014 ADM and suggestions for improvement. Rather than a written survey, person-to-person interviews of were completed to evaluate (1) how state agencies would use an ADM that addresses both drainage and stormwater management, (2) what topics it should include, and (3) their vision for the manual that expands its reach and establishes policy while restoring its past usefulness as a one-stop guide to advance transportation design policy and procedures.

Task 2. Sample Chapters and Phase II Work Plan

Sample Chapters

Two sample chapters were developed in Task 2, one based on a new topic and the second on an existing chapter in the 2014 ADM. Based on timing of other projects and research, the AOP chapter was developed as the new chapter given that information was generally available in the current literature. The 2014 ADM Energy Dissipator chapter was updated given the technical content was well established in the literature.

Phase II Work Plan

The other requirement of Task 2 was to submit the Phase II Work Plan including a proposed schedule and milestones for completion of each chapter and the total manual. Chapters that incorporated active research, or that used or referenced FHWA technical manuals or other reference documents currently being updated, were delayed as long as possible while still meeting deliverable dates.

Phase II

Task 3. First Draft

Task 3 developed a comprehensive first draft of the new highway drainage manual based on Phase I results. Key personnel on the Research Team were assigned to specific chapters to allow work to proceed on multiple chapters at a time. When the first draft of the manual was complete a workshop was held to discuss the Panel comments that had been provided in the margin of the draft document and obtain other feedback and guidance from the Panel.

Task 4. Second Draft

Task 4 updated the Task 3 draft document with the changes approved by the Panel. As with Task 3, a workshop was held to discuss the revised draft document and the comments provided.

Task 5. Final Version

A final version of the new highway drainage manual was prepared incorporating all the revisions based on the Task 4 results. As with Tasks 3 and 4, a workshop was held to discuss the final version.

Task 6. NCHRP Final Report

Task 6 was to prepare this report, the NCHRP Final Report, which was written to document the review and update process completed for the new highway drainage manual, including summarizing major differences from the 2014 ADM. The Final Report also identified suggested research needs that might improve design practice. Finally, given concurrent NCHRP, AASHTO, FHWA and NOAA publications under revision or development, the Final Report identified future updates needed in the ADM when these other publications become available.

Task 7. National Hydraulics Engineering Conference Presentation

A presentation was made at the 2024 National Hydraulics Engineering Conference (NHEC) to highlight the results of this project, and to promote adoption of the new highway drainage manual. The presentation materials developed were made available for use by Panel Members at other meetings and conferences.