Eliminating government employees' parking perks would generate an estimated $46 million in revenue for the city while helping to reduce traffic congestion, a new study says.The study, commissioned by Transportation Alternatives, an advocacy group, found government workers are twice as likely to drive to work in Manhattan's central business district as workers in the private sector.According to the study, 19,200 fewer vehicles would enter Manhattan each day if government workers were stripped of their free-parking perks and commuted at the same rate as their private-sector counterparts.The parking spaces freed up by these vehicles could generate $46 million annually in parking meter fees, the study says."You might think it's the stockbroker from Greenwich who drives to work," said Bruce Schaller, a transportation consultant who authored the study. "In fact, they're among the least likely people to drive to work. It's the government employee with free parking in Manhattan who is most likely to drive."The study found that 47,000 government employees, or 26% of the 177,300 government employees working in Manhattan south of 59th St., drive to work. Two-thirds of these government workers are employees of the City of New York.In April, the Daily News published an exclusive report about a Transportation Alternatives study that found 115 government-employee cars illegally parked on sidewalks or in pedestrian areas - many of them also blocking fire hydrants - during a single hour on March 29 in Chinatown and around City Hall.More than 90% of the illegally parked cars appeared to have city-issued placards that permit free parking only in legal spots when a government employee is conducting "official business."After The News published the report, the NYPD launched a crackdown on illegally parked city employees in Chinatown, issuing summonses and towing away cars, much to the relief of long-suffering business owners.Jordan Barowitz, a spokesman for Mayor Bloomberg, said the city has reduced the number of parking placards by 12% since last year.He pointed out that the mayor regularly rides the subway and encourages all public employees to use mass transit.