Traffic flows along the northbound lanes of Interstate 495 over the Christina River in Wilmington. Delaware is not one of the states where speed demons rule: The limit is 55 mph. (William Bretzger/The Wilmington News-Journal via AP)

In six states —Idaho, Maine, North Dakota, South Dakota, Texas and Wyoming — drivers can get up to 75 miles per hour on urban interstates, and oftentimes even faster on rural ones.

States have been able to set their own speed limits since 1995, when the federal government repealed the 55 miles per hour National Maximum Speed Limit. Since then, 35 states have raised their speed limits to 70 miles per hour or higher on at least some places, according to the Governors Highway Safety Association.

Maximum speed limit for cars on urban interstates by state

The above map shows maximum speed limits for cars on urban interstates, however, there are sometimes different speed limits posted for trucks, on rural interstates, and on state highways. Whether an interstate is classified as urban or rural is determined by the U.S. Census Bureau, which describes a location as urban if it is a continuously built-up area with a population of at least 50,000 people, or it is location with at least 2,500 people that is incorporated or has a densely settled population center. All other areas that don’t fit these descriptions are classified as rural.

In Texas, there are rural highways with speed limits as high as 85 miles per hour, the highest in the country, while some state highways are between 75 and 80 miles per hour. Wyoming and Utah also have stretches of interstate where vehicles can get up to 80 miles per hour, according to the Governors Highway Safety Association.

But higher speed limits have led to increased fatalities, according to a study published in the American Journal of Public Health in 2009. Fatalities increased by 3.2 percent, from 1995 when the National Maximum Speed Limit was repealed, to 2005, the study found, even as seat belt and child restraint use increased and dual front air bag laws were passed. It also found that fatalities actually declined for states that didn’t increase their speed limits but built more rural interstates.

“Reduced speed limits would save lives; they would also reduce gas consumption, cut emissions of air pollutants, save valuable years of productivity, and reduce the societal cost of motor vehicle crashes,” the study reads.