Actual speeds on the roads compared to the posted limits, final report 551. (2004). Arizona Dept of Transportation.
Engineering speed limits - FHWA safety program (2014). United States Department of Transportation - Federal Highway Administration, Office of Safety.
Elvik, R. (2012). Speed limits, enforcement, and health consequences. Annual Review of Public Health, 33: 225 -- 238.
Marvel, C.C. (2010). Meaning of "residence district," "business district," "school area," and the like, in statutes and ordinances regulating speed of motor vehicles. American Law Reports -- Annotated, 2nd Series, 50. The Lawyers Co-operative Publishing Company; Bancroft-Whitney; West Group Annotation Company.