Alcohol, drugs and fatigue are major contributors to traffic fatalities during the holiday season, according to the National Road Safety Foundation.

The holiday period from Thanksgiving through New Year’s is one of the most dangerous times on U.S. roads and highways, the agency said, with a spike in crashes that often result in serious injuries or death.

The increased risk is due to a combination of factors that include impairment from alcohol and drugs, coupled with a higher incidence of drowsy driving, according to the non-profit group that has been promoting safe driving through education for more than 60 years.

“Planning ahead, such as having a designated driver when going to holiday parties is a good way to travel safely,” said Michelle Anderson, director of operations at The National Road Safety Foundation. “Passengers can also play a role in keeping everyone safe by speaking up if a driver is impaired, drowsy or driving recklessly. Speaking up can prevent a tragedy marring the holidays.”

In 2021, 13,384 fatalities in motor vehicle traffic crashes involved alcohol-impaired drivers. This represented 31 percent of all traffic fatalities in the United States for the year, and a 14.2 percent increase from the previous year, the agency stated.

During the month of December 2021 , 1,013 people died in alcohol-impaired-driving crashes, according to the National Highway Traffic Safety Administration (NHTSA).

Christmas and New Year’s Eve were especially dangerous, with more drunk-driving fatalities than during any other holiday period, the non-profit added.

Male drivers are almost four times more likely than female drivers to be impacted by drunk driving, and young drivers up to age 34 accounted for the highest percentage (27 percent) of alcohol-impaired drivers in fatal traffic crashes in December 2021.

“The financial impact of impaired driving crashes is enormous – more than $44 billion every year in property damage, medical expenses and lost work time”, according to NHTSA.

Drugs, both legal or illegal, are another big factor in fatal crashes, the non-profit added. Some prescription drugs can also cause impairment or drowsiness.