LYNN – Ticked-off commuters vowed Monday morning to do more than grin and bear a titanic toll increase.Nena Forbes fumed as she waited in line at a Lynnway Dunkin’ Donuts drive-thru and estimated she will pay $120 more a month for her commute if tunnel tolls jump to $7 on Feb. 9.The Massachusetts Turnpike Authority increase approved last Friday must undergo public hearings before it is finalized.An Item analysis of the proposed hike estimates a commuter traveling 48 weeks a year will pay $1,680 under the new toll rate if they pay cash. A driver eligible for a proposed Fast Lane pass dollar discount would pay $1,440.Gov. Deval Patrick recommended the increase to help the Turnpike pay off debt related to the Central Artery project.At least two public hearings must be held before the authority can give final approval to the toll increases, which are expected to raise $100 million. One is scheduled for Dec. 11.Local legislators say doubling Sumner and Ted Williams tunnel tolls disproportionately saddles North Shore commuters with higher travel costs at a time when the souring economy is forcing everyone to pinch pennies.Forbes and fellow commuter Dan Longhurst said the hike leaves them with the option of bypassing the tunnels in favor of a longer Boston route or taking commuter rail or other public transportation.The Massachusetts Bay Transportation Authority made commuting a more expensive option last weekend when it increased parking rates at local lots including the Swampscott commuter lot and the Lynn parking garage.The one piece of good news for commuters is that an analysis of state highway data indicates that the multi-billion dollar Big Dig is doing what is was built to do: Push traffic bottlenecks out of Boston.