2015 was deadliest year on road since 2008

The number of people killed on the road in the U.S. soared 7.2% to 35,092 in 2015, marking the deadliest year on the road since 2008.

An uptick in driving tied to a better economy and lower gas prices helped contribute to the increase in fatalities, according to the National Highway Traffic Safety Administration.

But auto-safety regulators have still acknowledged a degree of surprise by the sharp increase. NHTSA and the White House asked experts to assess the causes of the increase.

"Despite decades of safety improvements, far too many people are killed on our nation’s roads every year,” U.S. Transportation Secretary Anthony Foxx said Monday in a statement. "Solving this problem will take teamwork, so we’re issuing a call to action and asking researchers, safety experts, data scientists, and the public to analyze the fatality data and help find ways to prevent these tragedies."

Though the increase was widely expected after NHTSA last month revealed a preliminary estimate of a 7.7% increase, the official figure solidifies 2015's dubious distinction as the first year-over-year increase since 2012. In addition, roadway deaths of pedestrians and cyclists hit a two-decade high in 2015.

To be sure, a 3.5% increase in miles driven contributed to the increase. What's more, nearly half of the people who died in an accident in 2015 weren't wearing their seatbelts, while one third were tied to drunken driving or speeding, according to NHTSA.

But the auto industry's steady improvements in vehicle safety over the last several decades — despite a litany of safety recalls — had driven down the number of roadway deaths to an all-time low of 32,675 in 2014.

The Obama administration has committed to pushing self-driving vehicle technology, believing that someday autonomous cars could eliminate roadway deaths altogether. But currently available technology is limited to some steering, braking and accelerating assistance, reckless driving alerts and parking help.

Follow Paste BN reporter Nathan Bomey on Twitter @NathanBomey.