BOSTON -- Parking in Boston has never been cheap, but now if you pull into a garage you'll find that the cost to park is through the roof, with prices rising faster than ever before.

Tell Us About Cheap Boston Parking

The Boston Globe reported that at least seven garages are now charging for parking in 20-minute rather than 30-minute increments.

Many of them are also collecting their all-day rates for periods of less than two hours. The all-day rate at one downtown garage is $33 and that kicks in after just an 1 hour and 40 minutes.

The average parking rate in Boston is $31 according to a 2006 report from Colliers International Property Consultants Inc., a real estate services firm -- and that was down $1 from the year before, according to the Globe. That's among the highest in the nation. Only New York City has higher rates at about $40 an hour.

The average nationally was $15.28, up from $14.04 the year before.

According to the newspaper report, Boston parking rates are high because demand for parking spaces is strong and the supply of spaces is limited. The Environmental Protection Agency has capped the number of parking spaces at downtown garages and lots at 35,303, to encourage commuters to leave their cars at home.