Why This Fourth of July Could Be Among the Deadliest in Recent Years on the Highways

A number of factors, from the economy to the calendar, are cause for concern.

— -- An estimated 35 million Americans will be on the roads this holiday weekend, according to AAA, and this year could be one of the deadliest in recent memory -- due to drunk drivers, experts said.

The National Safety Council, a nonprofit group, estimates that about 400 Americans will die on the roads this weekend, with drunk driving being the leading cause of fatalities.

While I strapped on the kit, U.S. Park Police Sgt. Adam Zielinski put me through the paces of a DUI stop, and I was staggering, unable to walk even nine steps in a straight line.

"Do you think that you were able to operate a vehicle safely?" Zielinski asked.

The answer was a clear no when I couldn't even get one foot in front of the other.

"So you have the possibility of people attending two different events, on a Friday and a Saturday," Zielinski said. "There's just a culmination of different effects that could really be an integral part on how highway safety is this weekend."

Heather Wedel, a spokeswoman for Mothers Against Drunk Driving, said that through through July 5, people can go to Uber.com/MADD and take the pledge to not drink and drive. Uber will match every donation made to MADD through this pledge page, dollar for dollar, up to $25,000, Wedel said, noting that the funds raised will be used to serve victims of drunk driving.