Traffic deaths in the United States rose 9.3 percent in the first nine months of 2015 compared to same period a year before as low gasoline prices increased road travel, the U.S. Transportation Department said on Friday.

The U.S. National Highway Traffic Safety Administration, a branch of the Transportation Department, did not immediately have an explanation for the increase in traffic deaths to an estimated 26,000 in 2015, which is the highest level since 2008.

These are the countries with the fewest road traffic deaths
Image: World Economic Forum

NHTSA said 94 percent of all crashes are the result of human error and that it is working to address driver behavior.

"We're seeing red flags across the U.S. and we're not waiting for the situation to develop further," NHTSA Administrator Mark Rosekind said. "It's time to drive behavioral changes in traffic safety and that means taking on new initiatives and addressing persistent issues like drunk driving and failure to wear seat belts."

The fatality rate was 1.1 deaths per 100 million miles traveled in 2015, compared with 1.05 deaths per 100 million miles the previous year. That is the highest fatality rate since 2012.

The northwestern United States reported a 20 percent increase in road deaths, higher than any other region.

U.S. traffic deaths had been falling with a 1.2 percent decline in 2014 and more than 22 percent from 2000 to 2014.

The pace of road deaths is greater than the growth in vehicle travel. The Transportation Department said last month that U.S. drivers logged 2.88 trillion miles in the first 11 months of 2015, up 3.5 percent over the same period in 2014, and on pace for the highest ever yearly total.

A drop in gasoline prices puts more Americans on the road, increasing the probability of accidents. Traffic was up 3.5 percent in first nine months of 2015, compared to the same period the year before.

Since 2014, automakers have addressed safety issues by recalling a record number of vehicles to fix defects amid greater scrutiny from regulators and Congress.