Updated November 28, 2014.

Although alcohol-related traffic fatalities have been on the decline in recent years, the certainty of highway deaths due to alcohol impaired drivers is so predictable each holiday period that many state highway patrol departments issue highway fatality "projections" each year that will turn out to be uncanningly accurate.

Ignoring the Warnings

Despite all the warnings, public awareness and educational programs, stiffer penalties for violations, and efforts by law enforcement agencies across the nation to be more visible and diligent in protecting the highways, people will still get behind the wheel of their vehicles while intoxicated.
Motor vehicle wrecks are the leading cause of death in the United States for persons under age 24, according to the Centers for Disease Control and Prevention Morbidity and Mortality Reports.

Of those deaths, more than 40 percent are alcohol-related.

Alcohol-related accidents are so prevalent, an estimated 40 percent of all persons in the United States will be involved in a traffic mishap blamed on alcohol at some point in their lives.

How Dangerous Is Drinking and Driving?

A driver with a blood alcohol concentration (BAC) of 0.10 or greater is seven times more likely to be involved in a fatal motor vehicle crash than is a driver who has not consumed alcoholic beverages, and a driver with an alcohol concentration of 0.15 or greater is about 25 times more likely.
Basically, the more you drink the more likely you are to have an accident, and a fatal one. The same applies for the likelihood of having any vehicle accident, fatal or otherwise. Here's the cold hard facts:

More Likely to Have a Crash

A 160-pound person drinking two beers within an hour would probably have a BAC of 0.04, well below the legal limits of driving under the influence, but 1.4 times more likely to have an accident than someone who is sober.
Two more beers?

The likelihood of an accident goes up almost tenfold. At .08 BAC, a driver is 11 times more likely than the non-drinking driver to be involved in a crash. As the amount of alcohol in the driver's system rises mathematically on the BAC scale, the likelihood of a traffic accident multiples.

Two more beers? Up to a six-pack now? The likelihood of having an accident is now 48 times higher than the abstainer and the driver has just now passed the 0.10 BAC level.

Play It Smart

Two more? Hey, you've already had a six pack, two more couldn't hurt, right? Except two more beers could put your BAC close to 0.15 at which point you are 380 times more likely to have an accident.
Play it smart during weekends and holidays. If you plan to party away from home -- and this includes on the water -- be sure to appoint a designated driver for the car or operator of the boat. Whatever you do, don't get behind the wheel if you've been drinking.

^Sources:

^{Centers for Disease Control and Prevention. Mortality Trends and Leading Causes of Death Among Adolescents and Young Adults. Morbidity and Mortality Weekly Report. 1993.National Institute on Alcohol Abuse and Alcoholism. Alcohol Alert No. 31. January 1996.}