District police charged 60 motorists with drunk driving early yesterday, including 49 arrested at a single sobriety checkpoint.

Officials said the checkpoint arrests, at the north entrance to the I-395 tunnel near Third Street and Massachusetts Avenue NW, represented the largest number of drunk driving arrests ever made at a single such operation.

The city's crackdown marked the start of an areawide effort by police to curb Labor Day weekend traffic accidents and drunk driving. Maryland State Police began using radar hidden in a yellow state highway dump truck to catch speeders.

By late yesterday, three persons had died in traffic accidents in Maryland and three in Virginia since Friday night. Police said alcohol consumption was a factor in two of the Maryland deaths.

The D.C. roadblock was operated from midnight to about 5:30 a.m. Saturday by teams of traffic police officers and alcohol enforcement officials. Traffic police said they arrested 11 motorists on drunk driving charges elsewhere in the District Friday night and early Saturday, to bring the total to 60.

"We were trying to make people aware of the upcoming Labor Day holiday and get them to stop drinking and driving," said a traffic division official.

Maryland and Virginia highway officials also praised the deterrent benefit of checkpoints have.

Meanwhile, Montgomery County Police reported that they were led on a chase that ended in a swimming pool after one motorist they stopped at a roadblock in Chevy Chase sped off when officers began to question him.

Police said the man was driving a late-model sedan that has been reported stolen in Seat Pleasant. The car was stopped about 2:15 a.m. on Wisconsin Avenue NW, just above the District line.

After a short chase, the car crashed through a fenced yard and into a swimming pool in the 4600 block of Chevy Chase Boulevard. The driver escaped, but a passenger, still in the swimming pool when police arrived, was arrested.