Federal Highway Administration (September 2004). "Excellence in Highway Design 2004". Focus: Accelerating Infrastructure Innovations. Vol. 21, no. 8. Federal Highway Administration. ISSN1060-6637. FHWA-HRT-04-029. Archived from the original on June 10, 2010. Retrieved February 12, 2006.
Federal Highway Administration (September 2004). "Excellence in Highway Design 2004". Focus: Accelerating Infrastructure Innovations. Vol. 21, no. 8. Federal Highway Administration. ISSN1060-6637. FHWA-HRT-04-029. Archived from the original on June 10, 2010. Retrieved February 12, 2006.
Federal Highway Administration (September 2004). "Excellence in Highway Design 2004". Focus: Accelerating Infrastructure Innovations. Vol. 21, no. 8. Federal Highway Administration. ISSN1060-6637. FHWA-HRT-04-029. Archived from the original on June 10, 2010. Retrieved February 12, 2006.