For the second year in a row, U.S. traffic fatalities have increased in a disturbing reversal of a mostly decade-long downward trend,  according to the National Highway Traffic Safety Administration. The reasons: a variety of reckless behavior, including speeding, driving while impaired and not wearing seat belts.

According to a report released Friday based on 2016 data, 37,461 people died on U.S. roads that year, an increase of 5.6 percent over 2015. In Pennsylvania, 1,188 people lost their lives; in New Jersey, the toll was 601 people, the NHTSA reported.

New Jersey saw a nearly 27 percent increase in alcohol-impaired driving fatalities, the fifth highest rate in the nation, while Pennsylvania alcohol-related deaths dropped 9.4 percent from 2015. Only Alaska, Iowa, Vermont and the District of Columbia had higher alcohol-related death increases, according to the report. Vermont topped the list with an 80 percent increase.

In more than a quarter of all fatalities – 27 percent – speed was a factor.

Nationwide, motorcycle and pedestrian deaths accounted for more than a third of the year-to-year increase. A 5.1 percent rise in  motorcycle fatalities claimed 5,286 lives, the largest number to die that way since 2008, according to the NHTSA. Of those who were killed, 41 percent were not wearing a helmet.

Just this week in Philadelphia, two motorcylists died in separate accidents on the Schuylkill Expressway.

The NHTSA report also included pedestrian fatalities, which rose 9 percent to 5,987 deaths in 2016, the highest number since 1990. "Pedalcyclist" fatalities increased by 1.3 percent, resulting in the most deaths – 840 – since 1991.

Authorities had attributed the dip in fatalities in previous years to safety programs that emphasized the importance of wearing seat belts and not driving while impaired. In 2016, more than 10,400 people who were not restrained died from injuries sustained in crashes, including 228 children who were 12 or younger, the NHTSA reported.