(AP)—A government report says the number of drivers who get on the road with alcohol in their systems has declined by nearly one-third since 2007, but there has been a large increase in drivers using marijuana and other illegal drugs.

The National Highway Traffic Safety Administration said the share of who test positive for alcohol has declined by more than three-quarters since the agency first began conducting roadside surveys in 1973.

But the latest survey also found that nearly 1 in 4 drivers tested positive for at least one drug that could affect safety.

The anonymous surveys have been conducted five times over the last 40 years. They gather data in dozens of locations across the country from drivers who agree to participate.