The number of people arrested for drunken driving has dropped sharply since the mid-1980s, even though there are more drivers on the road, the Justice Department said in a report released yesterday.

The report, compiled by the Bureau of Justice Statistics, compared arrests for driving while intoxicated from 1986 through 1997. The number of drivers increased by almost 15 percent in that time, but the number of DWI arrests declined by almost 18 percent, from 1.793 million in 1986 to 1.477 million in 1997.

As a result, the report said, the arrest rate for drunken driving declined by 28 percent, from 1,124 arrests per 100,000 drivers in 1986 to 809 per 100,000 in 1997.

Annual arrests for drunken driving dropped steadily between 1990 and 1994, when the number totaled 1.384 million. Annual arrests have risen slightly each year since then.

The overall decline in drunken driving arrests has come at a time of increased attention to the problem from organizations such as Mothers Against Drunk Driving. The report also suggested that it may be linked to a gradually aging driving population and to tougher treatment of those charged with the offense.

The report said that in 1997, 54 percent of licensed drivers were 40 or older, compared with 46 percent who were that age in 1986. The statistical analysis also showed a clear correlation between age and drunken driving arrests. Drivers 21 to 24 had the highest arrest rate in both 1986 and 1997. In both years, the arrest rate declined steadily after 24, with each older grouping of drivers accounting for fewer arrests.

Although the number of arrests has declined since 1986, there are more people who are under correctional supervision because of drunken driving now, suggesting that law enforcement authorities have toughened their treatment of offenders. The report said that 270,100 people were on probation or in jail or prison for drunken driving offenses in 1986 and that that number had climbed to 513,200 in 1997.

For every 1,000 DWI arrests in 1997, 347 offenders were under correctional supervision, more than double the rate in 1986. About 90 percent of these people were on probation.

According to the report, drunken driving offenders are older, better educated and more commonly white and male than others under correctional supervision. It said Minnesota had the highest arrest rate in 1997, followed by Washington state and North Carolina. The lowest arrest rates were in Rhode Island and Massachusetts.

Maryland's drunken driving arrest rate dropped from 964 arrests per 100,000 drivers in 1991 to 709 arrests per 100,000 in 1997. Virginia's arrest rate also declined, from 975 arrests per 100,000 drivers in 1991 to 643 arrests per 100,000 in 1997. The report did not include 1997 data for the District but said the arrest rate in the District increased from 672 arrests per 100,000 drivers in 1991 to 927 arrests per 100,000 in 1994.