U.S. highways have been emptier during the coronavirus pandemic, but they have also been more deadly, according to statistics released Wednesday.

The National Safety Council said preliminary data show that in March, when most Americans began to drive less because of pandemic-related stay-at-home orders, the fatality rate per mile driven went up by 14 percent compared with March 2019.

The traffic fatality data, compiled from all 50 states and the District of Columbia, confirm the alarming reports across the country that speeding and reckless driving during the health crisis are leading to a disproportionate number of crashes and fatalities.

“The risk on our roads has actually increased,” said Ken Kolosh, the council’s manager of statistics, who ran the data analysis. “Although an 8 percent decrease in deaths from one March to the next March is great news, that decrease should have been even greater if the risk on our roads had stayed the same. We should have seen closer to an 18 percent decrease in deaths.”

The overall number of fatalities went down by 8 percent, according to the report, a decline that is attributed to shelter-in-place orders and other restrictions across the country.

The number of miles driven dropped 18.6 percent in March compared with the same month last year, according to the council. But the death rate per 100 million vehicle miles driven was 1.22 in March, up from 1.07 in March 2019, the organization said.

The surge in speeding and reckless behavior on the nation’s roadways has alarmed police and road safety groups, and prompted increased patrolling on some highways and renewed calls for drivers to slow down.

As traffic volumes fell dramatically following the stay at-home orders, average speeds increased significantly above posted limits, more than doubling in some cities, traffic data show. Police agencies from New York City to Los Angeles reported more speed-related crashes. State troopers in Maryland, Virginia, California and Minnesota have reported writing more speeding tickets. Some drivers have been caught traveling at speeds topping 130 mph.

The National Safety Council numbers are the first official statistics confirming the trend, which experts think continued in April and this month.

“We really have to keep a very close eye on the trends going forward,” Kolosh said. “Unfortunately, with the anecdotal reports of risky driving, we fear that the fatality rate per hundred million miles traveled is going to continue to be elevated.”

Road safety advocates and police are urging people behind the wheel to slow down, not to drink and drive, and to wear seat belts.

About 40,000 people die on U.S. roads each year.

Over the Memorial Day three-day weekend alone, the council estimates 366 potential fatalities — the lowest number of fatalities for the holiday period since 2014, in part because fewer people are expected to travel.

Even with the 8 percent decline in fatalities in March, the council said road deaths were up 2 percent in the first quarter of 2020 compared with the same time period last year.