AMES, IOWA - DOT officially opposes any increase in the speed limit on Iowa’s Interstates and four-lane divided highways. A new report issued by the Iowa Safety Management System’s (SMS) Task Force on Speed Limits provides further evidence that an increase would be detrimental to the safety of Iowa motorists.

Responding to the report, Governor Tom Vilsack said, "This latest report is further proof that higher speed limits threaten the safety of Iowa citizens."

The task force’s 2001 updated report is a compilation of data gathered in Iowa and other states regarding the effects of changing speed limits on travel speeds, crashes, injuries and fatalities. Some key findings include:

• sections of Iowa expressway where speeds were increased from 55 mph to 65 mph in 1996 continue to show a higher frequency of fatal crashes since the speed limit change;

• crash and injury rates on Iowa expressways, before and after the speed limit increased from 55 to 65 mph, included increases of 28 percent for “fatal and injury” crashes, 23 percent for “all crashes,” 75 percent for “fatal plus major injuries,” and 26 percent for “other” injuries;

• the increased kinetic energy in a crash at higher speeds may contribute to more severe injuries. An 18 percent increase in speed from 55 mph to 65 mph results in a 40 percent increase in the kinetic energy associated with a moving vehicle. Increasing the speed from 65 mph to 70 mph (an 8 percent increase in speed) results in a 16 percent increase in the kinetic energy;

• in the year 2000 the 85th percentile operating speed on Iowa’s rural expressways and freeways was 4.7 mph above the speed limit (69.7 mph). The 85th percentile is the speed 85 percent of vehicles travel at or below, and 15 percent of vehicles exceed;

• more drivers are complying with the 65 mph speed limit when compared to compliance with the former 55 mph speed limit;

• speed costs money. The rule of thumb for all heavy trucks is that for every one mile per hour increase in average vehicle speed, there is a 2.2 percent increase in fuel consumption or a .14-mile per gallon decrease in fuel economy;

• for passenger cars, a vehicle speed increase from 65 mph to 70 mph results in a typical 10 percent decrease in fuel economy. Sport utility vehicles experience approximately a 20 percent decrease in fuel economy for an increase in speed from 65 mph to 75 mph;

• higher operating speeds also decrease component service life and shortens preventive maintenance intervals, increases oil consumption, and decreases tread life on tires and brake life;

• a comparison of total traffic fatalities for Iowa and surrounding states shows that states that did not raise speed limits above 65 mph (Iowa, Illinois and Wisconsin) experienced declines of 1.5 percent, 3.2 percent and an increase of 4.2 percent respectively.

• states that raised their speed limit above 65 mph (Kansas, Minnesota, Missouri, Nebraska and South Dakota) experienced an increase in their traffic fatalities ranging from 3.3 percent to 18.2 percent; and

• an analysis of fatalities from 1992 to 1995 and 1996 to 1999 reveals the collective fatality experience for Midwest states that did not raise limits above 65 mph was a 1 percent decline in traffic deaths, while states that did raise speed limits above 65 mph experienced a 10.7 percent increase in traffic fatalities;

Its membership includes representatives from the Iowa departments of Transportation, Public Health, Education, and Public Safety; Fire Service Institute, Iowa State University; AAA Minnesota/Iowa; American Public Works Association; Iowa State Sheriffs’ and Deputies’ Association; Cedar Rapids Police Department; Safety Circuit Rider Program, Center for Transportation Research and Education, Iowa State University; Iowa Traffic Control and Safety Association; Iowa Interstate Railroad; State Farm Insurance; Iowa Northland Regional Council of Governments; Iowa Division, Federal Highway Administration; and the National Highway Transportation Safety Administration, Region VII.

The SMS task force has previously issued reports on the subject of speed limits in 1996, 1997, 1998, 1999 and 2000. A copy of the 2001 report is available on the DOT’s Web site at http://www.dot.state.ia.us/speedrpt.htm