The MBTA expects to increase fares by at least 15 percent to 20 percent beginning this fall, Patrick administration officials announced Thursday, raising the specter that transit riders will have to pay both higher taxes and more for their CharlieCards by year's end as part of the state's efforts to fix its transportation systems. The Massachusetts Bay Transportation Authority will also propose a series of service cuts that could possibly limit, but not eliminate, the fare increase. 'It's getting out of hand,' said Stacey Jones-Walker, 48, a Dorchester resident who uses the T to commute to two jobs. 'It's crazy.' Speaking at Thursday's board meeting, state Transportation Secretary James A. Aloisi Jr. said a fare hike would be necessary even if the agency receives an expected $160 million from the Legislature next month as part of an increase in the state sales tax. If the Legislature does not send the T any additional money, Aloisi has said, the effect on fares and services would be far more drastic. 'We need to have a multiyear solution,' said Aloisi, who is also chairman of the MBTA board. He said he wants to raise enough money to avoid another fare increase for a 'minimum of two, hopefully three fiscal years.' Over the next few weeks, Aloisi said, he has asked MBTA managers to produce a menu of options for fare hikes, as well as service cuts, and then begin the legally required public hearing process in time for a fall increase. The extent of service cuts will depend on the size of the fare hike and may be eliminated, depending on public response, he said. While Aloisi said he expected the fare proposal to be in the range of 15 percent to 20 percent, he indicated it could be higher, but would not exceed any of the three previous fare hikes, which were between 25 percent and 27 percent. The T last raised fares in January 2007, to $2 for a one-way subway ride, though most people pay no more than $1.70 using an electronic CharlieCard or a monthly pass. 'No one, especially me, takes a decision to raise fares or cut service lightly,' Aloisi said Thursday. 'Our decisions will impact people's lives.' Both House and Senate have approved raising the sales tax from 5 percent to 6.25 percent, and lawmakers are now negotiating the details of their budget before passing a final version. Leaders have said they expect to allocate about $275 million from the tax increase to the state's transportation needs. Aloisi and legislative leaders have said they expect to have about $160 million available for the T. Though the T's deficit officially stands at $160 million for the budget year that begins July 1, Aloisi and MBTA managers say it has been growing larger than that in recent weeks and will get larger in the following years. The soft economy has diminished the agency's advertising intake for the next budget year, and the T recently learned that it will need to pay $9.6 million more than expected on a new contract for its disabled riders transit service. Governor Deval Patrick proposed increasing the gas tax by 19 cents, which would have raised more than $600 million for transportation needs, including $165 million for the T. Aloisi said that if the Legislature had approved the increase in the gas tax when it was proposed, there would be no need for a fare hike. Aloisi also said he fears that the Legislature will not agree to enough significant changes in MBTA worker benefits to save the money necessary to put the T on stronger financial footing. The House and Senate are negotiating a transportation overhaul bill. Initial versions were criticized by watchdogs for not saving enough money. Key legislators have long said that T riders would probably not be spared a fare increase, even if the state comes through with a rescue for the agency. 'It is unreasonable to think that there wouldn't be adjustments in fares periodically,' said Representative Joseph F. Wagner, a Chicopee Democrat and cochairman of the Legislature's Transportation Committee. Wagner said the transportation overhaul will provide cost savings. And he pointed out that the T already gets 1 percent of the state sales tax annually as a subsidy, meaning that the agency will get close to $900 million a year once the additional subsidy is taken into account. The T is weighed down by a debt load of more than $8 billion, which absorbs nearly a third of its operating budget every year, as well as high operating costs and worker benefits. Some unions have agreed to forgo a 4 percent increase due July 1, but the T's largest union, the Carmen's Union, has not responded to a management request to make a similar concession. Aloisi has previously said that fares could go up by 30 percent if the Legislature does not act. The agency had also been preparing for the possibility of significant service cuts, including, for example, the end of weekend and evening commuter rail service and the elimination of some bus routes, according to documents obtained by the Globe. Some transit advocates have faulted Aloisi for waiting too long to release details of fare hikes and service cuts and say he should not be assuming the agency will get the full $160 million from the Legislature. Carrie Russell, a staff attorney for the Conservation Law Foundation, said it is irresponsible to wait any longer to release details of the fare hikes and service cuts because commuters are losing the chance to affect the debate. By the time the state begins public hearings, the debate could be over, she said. 'The public will be forced to comment only on which fare increases or service cuts take effect, rather than whether fare increases or service cuts should take effect,' she said. Noah Bierman can be reached at nbierman@globe.com. 