NEW YORK (CBSNewYork) — Thursday is the shortest day of the year.

Officials warn that the darkest week of the year is often the deadliest for pedestrians.

“When the days are the darkest and the most people are out on the street the dusk hours have been the most dangerous time of the entire year,” said DOT Commissioner Polly Trottenberg. “More pedestrians are hurt in crashes at dusk at this time of year than at any other time of the year.”

Trottenberg said that at dusk from November through March severe and fatal pedestrian injury crashes were 40 percent higher than the rest of the year.

City transportation officials are stepping up safety efforts at twilight time and the NYPD is launching DWI checkpoints for the holidays. There will be stepped up enforcement around schools, senior centers and shopping areas.

The warnings and increased enforcement are based on science.

“We talked to vision experts who told us that the low light at dusk makes it very difficult for our eyes to focus properly,” Trottenberg said.

But NYPD Transportation Chief Thomas Chan said it’s not just drivers who need to pay attention.

“Unfortunately I still see even pedestrians walking across the street, looking at their cell phones,” Chan said.

With the launch of the DOT’s Dusk and Darkness safety campaign, fatalities were down 25 percent last year.