The Influence of Speed Limit Policy on Traffic Safety.

Previous attempts to conduct the connection between speed limit and traffic crashes focus on short-term periods and a specified or limited states after the National Maximum Speed Law (NMSL)of USA changed. The long-term period variety of the fatalities and fatality rate of the whole United States are proposed in this paper when the federal speed limit law was repealed. The macro factors such as gross domestic product (GDP), number of vehicle et al. are considered to conduct the influence of traffic safety after the NMSL was repealed. The negative binomial regression model is proposed to analyze the impact by the data collected from 1975 to 1995. The prediction that it would be if there is no speed limit change can be obtained and the deviation between the prediction and the actual from1996 to 2015 can be estimated. It can be found that fatalities have significantly increased (maximum is 9.3%)than the typical in most (8 years)of the first 10 years since the NMSL was repealed. The fatality rate has no significant increase in the first 10 years. There is no significant change in the long-term (10–20 years)period.