Traffic fatalities in the U.S. rose 7.7% in 2015 compared to the previous year, with pedestrians, bicyclists, and motorcyclists accounting for the most significant increases, according to preliminary data released by the National Highway Traffic Safety Administration.

An estimated 35,200 people died in crashes in 2015, up from the 32,675 reported fatalities in 2014. Although the data are preliminary and require additional analysis, the early NHTSA estimate shows nine out of 10 U.S. regions saw more traffic deaths in 2015, the federal agency reported.

“We are analyzing the data to determine what factors contributed to the increase in fatalities and at the same time, we are aggressively testing new safety technologies, new ways to improve driver behavior, and new ways to analyze the data we have, as we work with the entire road safety community to take this challenge head-on,” said U.S. Transportation Secretary Anthony Foxx.

NHTSA is an agency within the Department of Transportation.

The fatality rate for 2015 climbed to 1.12 deaths per 100 million vehicle miles traveled – up from 1.08 deaths per 100 million vehicle miles traveled in 2014.

Actual counts for 2014 and 2015 will be further revised as the final file for 2014 and the annual reporting file for 2015 become available later this year, NHTSA said. The agency is continuing to gather crash fatality data from police reports and other sources.

“The fourth quarter of 2015 represents the fifth consecutive quarter with year-to-year increases in fatalities as well as the fatality rate,” NHTSA reported. “The magnitude of the increases has also been rising up to the 11-percent increase in the third quarter of 2015. Fatalities are projected to have increased by 4.7 percent during the fourth quarter of 2015.”

Since 94% of crashes are tied to human error or faulty decision-making, NHTSA is focusing safety efforts on improving driver behavior and promoting vehicle technology designed to prevent crashes and protect occupants when they occur. The agency held six regional summits in February and March aimed at developing new tools to improve the fight against such threats as drunk, drugged, distracted, and drowsy driving as well as speeding.

Increasingly, NHTSA said, it is engaging with local elected officials, scientists, and policy experts to search for new solutions to improve traffic safety.

The Governors Highway Safety Association released a statement calling NHTSA’s initial estimates “alarming” and pointing out that the 7.7% jump represents the largest year-over-year increase in traffic deaths since national recordkeeping began.

“The good news is that the solutions to reducing traffic deaths aren’t a mystery,” GHSA said. “They include strong laws coupled with highly visible law enforcement and robust public education campaigns. By using these tactics, the nation saw a nearly 25 percent drop in the number of fatalities between 2005 and 2014, including a record low in 2011.”