The price of street parking at one-hour meters in downtown Washington and adjacent neighborhoods is going up a dime to 50 cents an hour, the D.C. Department of Transportation announced yesterday.

Workmen will start converting the 4,500 affected meters Monday morning in a changeover that will require several weeks, according to Fred Caponiti, chief of parking operations for the transportation department.

Until all the meters are converted, the price will be whatever rate is posted on the meter-either 40 or 50 cents an hour.

Meter parking costs have been rising steadily since the mid-1960s, when the price was 10 cents an hour.

Caponiti said the new increase follows a policy of keeping meter rates at about half the cost of hourly rates for commercial garages and lots. This keeps the cost of all-day meter parking above all-day commercial rates and discourages commuters from trying to save money by parking on the streets and feeding meters, Caponiti said.

The cost of parking at two hour meters will not be changed from 40 cents an hour, a rate set last year. The cost of parking at short-time meters with limits under an hour also will remain unchanged.

The area covered by the new rate is south of Massachusetts Avenue from Glover-Archbold Park on the west to 17th Street SE on the east. In addition to downtown, this includes Georgetown, Foggy Bottom, Capitol Hill and the Southwest renewal area.

Caponiti estimated the increase would add about $300,000 a year to current parking meter revenues of about $3.8 million. CAPTION: Picture, no caption, The Washington Post