The latest study by the National Highway Traffic Safety Administration (NHTSA) shows that drunk driving had declined by nearly a third since 2007 and by more than 75% since the first survey was completed in 1973. While that is very good news, the less-good news is that the number of drivers using at least one drug that could affect safe driving has risen to nearly 25%.

According the NHTSA survey, about 8% of drivers during weekend nighttime hours were found to have alcohol in their systems, and slightly more than 1% were found to have a breath alcohol level of 0.08% or higher.

Weekend nighttime drivers who showed evidence of drugs in their systems rose from 16.3% in 2007 to 20% in the 2014 survey. The number of drivers with marijuana in their systems rose by nearly 50%, according to the survey.

In a separate survey to assess whether marijuana use is associated with greater risk of accidents, the NHTSA reports that marijuana users are more likely to be involved in accidents, but the increased risk might due in part to the fact that marijuana users who drive under the influence are more likely to be in a group that already demonstrates higher risk — young men.

The U.S. Centers for Disease Control and Prevention says that more than 10,000 Americans were killed in 2012 in alcohol-related crashes, or about a third of all traffic-related deaths in the United States. Other drugs were involved in about 18% of traffic deaths.

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