The search for parking space is becoming a more costly pursuit in the commercial centers of Bethesda and Silver Spring, where fees for some of the 14,200 spots are doubling, Montgomery County officials announced. The fees are being raised to help pay for parking facilities in those areas and to encourage the use of public transportation, they said.

A 25-cent increase in meter fees went into effect April 1, but the parts to convert the meters won't be available until next week at the earliest, said Joseph L. Tracey Jr., the county's parking division chief. He said it may take up to half a year to complete the change.

The fee for short-term parking has gone up from 25 cents an hour to 50 cents.

Starting July 1, rates in long-term lots will go from 15 cents an hour to 25 cents an hour. Monthly permit prices will also rise, from $24 to $45.

But for the time being, Tracy said, "there will undoubtedly be instances where you can shop for a space a block away that will be cheaper, because we won't yet have the meter in place. But, it's just not something that can get done overnight."

Originally proposed was a more complicated rate system based on distance from Metro stations, with spaces nearest the Metro stations being the most expensive. But Tracy said the new system would be easier to enforce than the graduated fee structure.