Part of the increase in road deaths can be explained by the improving economy, higher employment numbers and low gasoline prices, all of which are causing Americans to drive more than they did just a few years ago, during the depths of the recession.

In an interview in October, Mark Rosekind, the N.H.T.S.A. administrator, said the increase in miles traveled was not enough by itself to explain this spike in crashes, injuries and deaths. Indeed, fatalities are occurring more frequently even when the increased travel is factored in.

Mr. Rosekind and other safety experts think one factor is distracted driving. In their view, distractions and the allure of smartphones, other devices and in-car electronics have multiplied greatly since the dangers of distracted driving entered the national consciousness years ago.

At that time, the main phone-related distracting activities were texting and talking on the phone. Now a wide range of apps and games also tempt drivers to reach for their phones.

Niantic, the maker of Pokémon Go, recently modified the game to prevent it from operating while moving at speeds of more than about 10 miles per hour, a spokeswoman for the company said. She declined to give further details on the modifications because Niantic did not want users to find ways to get around them, she said.

The change was made after a spate of accidents was blamed on drivers who were playing the game while at the wheel.

“I don’t think Pokémon Go is something any driver should be using at any speed,” Mr. Foxx said.

Makers of smartphones have added some technology that can be used to reduce the distraction of electronics. Apple’s iPhones have a do not disturb feature that can block incoming calls and texts, and a silent mode that eliminates the chimes and other audio cues that signal the arrival of a new message or posting on Facebook.