More than half the drivers who park in midtown and downtown Manhattan don't have to pay for their own parking, according to a study released Thursday.Some experts argue that inexpensive parking is responsible for much of the city's traffic congestion, and recommend charging more to force people to take mass transit.Click here to find out more!"Low-cost and free parking encourages driving," said Graham Beck, a spokesman for Transportation Alternatives, a city advocacy group which commissioned the study. "If the city were to manage parking it could greatly reduce the number of drivers who come into Manhattan."Also, when it's cheaper to park on the street than in a garage, drivers either circle in hopes of landing a spot or they double park, according to the report.Transportation expert Bruce Schaller, of Brooklyn, found that 38 percent of drivers had parking provided for them or were reimbursed for the cost. Another 19 percent of more than 1,600 drivers had found free street parking in Manhattan south of 59th Street.In addition to making it cost more to park on the street, yesterday's report recommended reducing the availability of placards that many government workers use to park for free and making it more expensive to drive in the busiest places.Private companies should limit how much parking they provide or offer incentives to not drive.But not surprisingly, a few drivers interviewed Thursday panned the idea of making street parking more expensive."I feel bad for the people who couldn't afford it," said Jaime White, 35, of Yonkers, who described herself as "lucky" to find a spot in Brooklyn Thursday. "It's going to make it more elitist."Kathryn Wylde, president of The Partnership for New York City, said the group of business leaders recommended studying the issue of increasing charges for on-street parking, but recognized that residents would raise objections.The group is planning to meet soon with UCLA urban planning professor Donald Shoup, author of a book called "The High Cost of Free Parking." He advocates that cities charge a market rate for street parking, with the goal of keeping a 15 percent vacancy rate. Ensuring there are some spots available makes it easier for delivery trucks and drivers making quick stops, he says.Wylde said a special challenge for New York is that so many residents live in the city's business districts."While in theory, raising on-street parking charges can accomplish the goal of discouraging people from driving cars and raising money, the people who are penalized in that equation tend to be local residents and their guests," she said, "as opposed to people coming into the business district from the outside."