Mahdi Sahafnia - Department of Civil Engineering, University of Kansas, Kansas, USA

Deciding which speed limit is ideal for each highway with has its own characteristics is a very important factor in designing the highways. Therefore, investigating proper highway speed limit can provide more safety for vehicles, reduces the number of crashes and fatalities and more importantly can save lives. The state of Kansas had the speed limit of 70 mph until June 2011. After that the state increased the speed limit to 75 mph. There are a lot of studies and investigations to show how increasing the speed limits affects the highways safety and the number of crashes. Some of the studies show no effects on the number of accidents and fatalities however some others show an increase in crash numbers. Therefore, each highway needs to be investigated separately for a better and life saving result. This paper investigates the effects of increasing the speed limit on the highways of I-70 and I-35 inside the Kansas State border. The number of crashes, injuries and fatalities before increasing the speed limit and after increasing the speed limit were analyzed. The data, which is used for this paper were provided by the Kansas Department of Transportation (KDOT). The time frame of this investigation includes the years of 2008 till 2011 and 2011 till 2014.