1. “1924 First of a Kind highway Safety Conference Takes Place in Washington, D.C.”, Transportation History, American Association of State Highway and Transportation Officials (AASHTO), https://transportationhistory.org/2021/12/15/1924-a-first-of-a-kind-highway-safety-conference-takes-place-in-washington-d-c/. Accessed April 23, 2023.
2. National Interstate and Defense Highways Act (1956), Milestone Documents, National Archives, Februjary 8, 2022. https://www.archives.gov/milestone-documents/national-interstate-and-defense-highways-act, Accessed April 23, 2023.
3. FHWA. Highway Functional Classification: Concepts, Criteria and Procedures. FHWA-PL-13-026, FHWA, Washington, DC, 2013. HwyFunctionalClassificationConcepts.pdf.
4. An Expanded Functional Classification System for Highways and Streets
5. Developing an Expanded Functional Classification System for More Flexibility in Geometric Design