PDF - http://www.ghsa.org/html/publications/pdf/surveystates2005/surveystates_speeding.pdf
"This most recent Survey of the States report summarizes efforts to reduce speeding-related fatalities and also provides a snapshot of individual state countermeasures. Of the 50 GHSA jurisdictions that responded, 38 indicated a speed limit increase since 1994. In releasing the report, GHSA notes that states should have experienced a significant decline in speeding-related fatalities given the tremendous gains in safety belt use coupled with the increasingly safe design of vehicles. However, statistics indicate speeding-related fatalities have remained fairly level since NMSL was repealed, which would indicate the safety benefits have been minimized by increasing speeds. A total of 47 states, one territory, the Indian Nations and the District of Columbia contributed data and information for the report."
Executive summary - PDF - http://www.ghsa.org/html/publications/pdf/surveystates2005/speeding_intro.pdf