Have fatalities notably increased since South Dakota raised its speed limit to 80?

South Dakota is one of eight states that has posted speed limits of 80 mph on sections of interstates, but it hasn’t resulted in a noticeable increase in fatalities. 

The state increased its speed limit from 75 to 80 in 2015. Since then, fatalities in crashes on highways and interstates have stayed relatively flat. There were 135 in 2014, the year before the speed limit change, and 134 in 2015. In 2024, there were 140 fatalities. 

The state’s highway fatalities peaked at 203 in 2003.

Improved technology and structural designs are a big factor in the improvement. In 1997, the occupant fatality rate per 100,000 registered vehicles was 17.81. In 2017, it was 10.05. 

Nationally, however, fatality rates on highways and interstates go up by 8.5% every time the speed limit is increased by 5 mph, according to a 2019 study.