LYNN – Opposition to dramatic road and bridge toll hikes in Greater Boston is gaining momentum through grassroots organizations and online rallying sites.The vociferous outcry, stemming from Web sites such as www.stopthepikehike.org, comes just as a series of four public hearings is about to commence, including one in Lynn on Dec. 15.The Massachusetts Turnpike Authority’s Board of Directors voted last month to increase tolls, in some cases doubling the amounts. For example, the revised rate scheduled, effective Feb. 9, doubles the Sumner Tunnel and Ted Williams Tunnel tolls from $3.50 to $7.A rally organized by the Stop the Pike Hike campaign was held Wednesday in East Boston. The goal was to gather petition signatures, raise awareness of the pending toll increases, and advise commuters and other concerned citizens on how to fight the plan by contacting legislators.The upcoming public hearings are as follows:- Boston, Dec. 10 – at the State Transportation Building, 10 Park Plaza, second floor, 6:30-8:30 p.m.- Lynn, Dec. 15 – at City Hall, 3 City Hall Square, 6:30-8:30 p.m.- Framingham, Dec. 17, Framingham Memorial Building, Nevins Hall, 150 Concord St., 6:30-8:30 p.m.- Worcester, Jan. 7, City Hall, 455 Main St., 6:30-8:30 p.m.The Turnpike Authority will accept oral testimony on the toll structure changes during these public hearings. In addition, written testimony and comments will be accepted for one week following the hearings, until 5 p.m. on Wednesday, Jan. 14.Written testimony and comments should be sent to the Office of the General Counsel, Massachusetts Turnpike Authority, 10 Park Plaza, suite 4160, Boston, MA 02116.The toll increases were proposed by the state agency as a way to pay down debt related to Boston’s Big Dig project.If allowed, the tunnel tolls would increase from $3.50 to $7 for cars paying cash and from $3 to $6 for vehicles using a Fast Lane pass. Two-axle commercial vehicles would pay $9, up from $5.25. All other commercial vehicles would pay $3.50 per axle.At the Allston-Brighton tollbooth, cars currently paying $1.25 would pay $2. Cars using a Fast Lane and now paying $1 would pay $1.50. Commercial vehicles would pay $1 per axle. The Weston tollbooth would see identical increases.The non-partisan Stop the Pike Hike campaign, founded by Michael P. Kelleher of East Boston, has created a Web site that provides users with an electronic means to print out a free decal, sign an opposition petition and keep updated on the issue.According to Stop the Pike Hike, shifting the transportation burden is no solution to paying off a $450 million debt. Kelleher equated the situation to the Boston Tea Party, in which American colonists revolted because they were forced to pay taxes but received no representation from the British government. As he put it, “First tea, now tolls.”Rep. Steve Walsh, a Lynn Democrat, has filed a bill that would halt all toll increases until Dec. 31, 2009 or until the Legislature can offer a more equitable transportation system overhaul master plan as an alternative.At Wednesday’s State House hearing, a transportation expert testified that creating a public-private partnership to run the Massachusetts Turnpike could leave the state with enough funds to use on other transportation needs. Leonard Gilroy of the Reason Foundation of Los Angeles said Chicago received $1.8 billion when it entered into a 99-year lease for the Chicago Skyway, while Indiana got $3.8 billion when it signed a 75-year lease for its toll road. Both governments then used the money to make transportation improvements elsewhere, Gilroy said.State Sen. Steven Baddour said the idea deserves discussion. Rep. David Linsky of Natick clarified that leasing the Turnpike wouldn’t necessarily spare MetroWest residents from a doubling of tolls if it requires the continued existence of tollbooths.North Shore commuters are still saddled with the highest toll costs for entering or passing through Boston.