© Raymond Boyd - Getty Images Study finds crashes are up 17 percent on roads with the higher speed limits—and four times as many people driving on them now exceed 80 mph.

Michigan raised the speed limit by 5 mph on more than 600 miles of rural highways in 2017.

In 2018, crashes on those roads went up 17.2 percent, compared to just 3.4 percent statewide, Michigan's Bridge Media reported.

Other states have also seen more injuries and deaths in places where speed limits were increased.

Speed can still kill. That's the lesson Michigan is learning on the 600-plus miles of rural freeways where the speed limit was raised from 70 mph to 75 mph thanks to a 2017 law. With the number of drivers now going over 80 mph on the increase, more people are getting into crashes and losing their lives.

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Bridge Media analyzed state police records and found that roads with the new 75-mph speed limit had, on average, more crashes and injuries in 2018 (the full first year for the new limits) compared to the entire road network. While the statewide average for crashes rose 3.4 percent in 2018 compared to the annual average from 2014-16 (remember, the speed limits went up part of the way through 2017), the average on the 75-mph roads went up 17.2 percent, Bridge Media found.

40 Percent Drive 80+ MPH on 75-MPH Roads

The real-world average speed increase on the 75-mph roads in one single-day test sample was just under 2 mph (from 74.6 mph in 2016 to 76.9 mph in 2018), but the total number of people going over 80 mph went from 10 percent to 40 percent of all cars. The result for some rural Michigan roads is that plenty of people are still driving well under 75 mph, but more are now going even faster.

© Cyrus McCrimmon - Getty Images North bound traffic on Interstate 25 is congested on the afternoon of Friday, February 15, 2002. This stretch of interstate is one of the most dangerous in the state. The speed limit is 75 miles per hour through this area north of Denver and Longmont.

Increased Danger Not Found Everywhere

Crash and death statistics from other states that raised their speed limits do not follow the same pattern. In Utah, for example, the number of crashes on some parts of I-15 in the state dropped between 2008, when the speed limit was raised to 80 mph, and 2014, when the data was analyzed, according to local news reports. In Montana, though, highway fatalities were 17 percent higher in 2015 than 2014 after the speed limit was raised from 75 mph to 80 mph in October 2015. The speed limit change was just one possible reason for that increase, as the fatality spike coincided with lower gas prices (which increases vehicle miles traveled) and more snow and ice on the roads that year than the previous year.

In 2013, the Connecticut General Assembly released a letter summarizing a 2006 National Cooperative Highway Research Program report. That organization found an "increased likelihood" (by 28 percent) of fatalities when a speed limit was raised from 55 to 65 mph. Going from 65 mph to 75 mph also found a minimal increase (0.6 percent) in the total number of crashes alongside a larger increase (13 percent) in the number of total fatalities. The Assembly said that the smaller increase in fatalities at higher speeds could be due to the fact that "people may drive more cautiously when driving faster, or that roads deemed appropriate for a 75-mph limit are safer." The Assembly also cited an American Journal of Public Health study that "found about a 3.2 percent increase in road fatalities attributable to the raised speed limit on all roads in the U.S." over a 10-year period.

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Michigan state legislators who spoke with Bridge Media said they specifically selected segments of roads that would be the safest places to increase the speed limit, the "lowest of the low-hanging fruit from a risk perspective," according to Brad Wieferich, director of MDOT's Bureau of Development. That may be true, but that hasn't stopped the rise in the number of crashes and injuries.