City police would find it easier to prove cases of drunken driving in the District under legislation tentatively approved by the D.C. Council last week.

The council also gave initial approval to a bill that would require the city's burgeoning sidewalk cafes to meet strict new regulations before their owners could build all-weather enclosures around them.

The drunken driving measure, introduced by council member Polly Shackleton (D-Ward 3), would change significantly the city's interpretation of blood-alcohol ratios.

Drivers who show a .10 ratio--which an average-size male usually reaches when he consumes four drinks in a hour--would be considered legally drunk. Under the current statute, that rate is only an indication or presumption of drunkenness. The new presumption of drunkenness level would be .05.

If a driver refused to take breath tests, prosecutors would be able to use that information in court. Current law forbids prosecutors from disclosing whether a person refused the test.

Penalties for first offenders would be reduced slightly, a move which supporters of the bill say would encourage more prosecutions and eliminate the need for jury trials. Penalties for subsequent convictions would be increased, however.

Under the proposed law, a first offender could be sentenced up to 90 days in jail and fined up to $300. A second offense could bring imposition of a $5,000 fine and a year in jail. Additional offenses would make the offender subject to a fine of up to $10,000 and a year in jail.

The council approved the enclosed sidewalk cafe measure after easily turning back an effort to exempt or "grandfather" about 25 existing cafes that have a variety of structures of differing quality around them.

Since a 1977 Superior Court ruling that the District's laws were vague and unenforceable, city officials have exercised little control over the construction of structures around the sidewalk cafes.