Despite the obvious dangers, an estimated 30.6 million Americans drive drunk during a given year,  and 10.1 million drive while high on drugs.

The estimates come from a survey of drivers by the Substance Abuse and Mental Health Services Administration, part of the U.S. Department of Health and Human Services. It found that 13.2 percent of Americans surveyed admitted to having gotten behind the wheel of a car while inebriated at some time during the previous year. Another 4.3 percent confessed to driving under the influence of illegal drugs.

Federal officials expressed concern about the findings, which covered 2006 to 2009.

“Thousands of people die each year as a result of drunk and drugged driving, and the lives of thousands of family members and friends left behind are forever scarred,” said SAMHSA boss Pamela S. Hyde. “Some progress has been made in reducing the levels of drunk and drugged driving through education, enhanced law enforcement and public outreach efforts. However, the nation must continue to work to prevent this menace.”

There was, as one might expect, significant variation between different age groups, with the proportion of drunk drivers ages 16 to 25 far higher than that for people 26 and up (19.2 percent versus 11.8 percent).

There was also a great deal of difference from one state to another; generally speaking, the highest levels of drunk driving were found in cold-weather states in the Upper Midwest and New England. Wisconsin led the field, with 23.7 percent of drivers copping to driving while intoxicated. On the other side of the spectrum, 7.4 percent of Utah drivers reported having driver drunk.

While such high numbers may be unsettling, they actually represent an improvement. A similar study based on surveys taken from 2002 to 2005 showed 14.6 percent of American drivers admitting to driving drunk in the 12 months prior, and 4.8 percent of respondents having driven while under the influence of drugs.