Drunk, drugged and distracted driving: the three dangerous Ds when you get behind the wheel. But a new report shows people should be concerned about a fourth:  drowsy driving.

A study by the Governors Highway Safety Association estimates 5,000 deaths per year from people nodding off while driving, with more than 50 percent of drowsy driving crashes involving drivers who are 25 years old or younger.

Jennifer Pearce knows the danger firsthand. She lost her 18-year-old sister, Nicole Lee to a car crash in 2008 when the driver fell asleep and drove head-on into a tree.

"When your family goes through something like that and you watch your parents, your sisters and brothers, your nieces, your aunts and uncles all experience so much pain, you want to do whatever you can to prevent that from any other family having to go through those same kinds of pain," Pearce said.

While not quite as fatal as drunken driving, the risks of driving while tired are similar to driving under the influence: slower reaction times and less attention paid to the road. 

"It's a bigger problem than we previously thought, and we also know there are some measures that can be taken to address it," said Kara Macek, a spokeswoman for GHSA. 

The solution, experts say, is simple: get more sleep and don't drive drowsy. 

"It's a culture issue," Pearce said. "We here in this country have a culture issue around sleep."

She wants parents to discuss with their kids the dangers of driving drowsy in the same way they discuss drunken driving and set good examples themselves by getting enough sleep.

"It's not easy, but I think my sister's legacy is to be sort of a beacon for this topic," she said. "I hope her story allows people to see that it can happen to an everyday average person."

The report also advises the public health, business, academic and nonprofit industries to come together to change the culture around sleep. Pearce and her family are working on starting a nonprofit in Lee's honor to spread awareness about the issue.

Today, only two states, New Jersey and Arkansas, have laws that penalize drowsy drivers who injure or kill someone.