With plans to open debate on its version of a $46 billion state budget on Tuesday, Senate leaders are weighing a raft of major policy proposals offered by senators as amendments to the legislation, including efforts to head off MBTA service reductions.

Senators filed 473 amendments to the annual state spending bill, which is currently four-and-a-half months overdue. Legislative leaders hope to wrap up the bill for Gov. Charlie Baker to sign by the end of the month, and have cautioned against making major additions to the framework negotiated between the branches in the interest of preventing the budget from getting bogged down.

Still, the House added an expansion of abortion access to its budget bill, and Senate President Emerita Harriette Chandler filed a similar version of the ROE Act as an amendment to Senate budget.

With the MBTA proposing drastic service reductions in response to reduced ridership, Sen. Jason Lewis filed an amendment that would prevent the agency from closing commuter rail stations and eliminating transit services, including bus routes, that would "unduly harm public transit riders."

Lewis is proposing to increase the state's operating transfer to the MBTA from $127 million for $435 million this year. Sen. Patrick O'Connor filed a more parochial amendment to prevent the T from eliminating the Hingham-Hull ferry, and requiring the agency to maintain 25 percent of its service capacity.

Senate Ways and Means Chairman Michael Rodrigues last week made clear that he had little appetite for adding tax hikes to the budget, which the House also rejected. But that didn't stop members like Sen. Jo Comerford from filing for an increase in the corporate excise tax or Sen. Joe Boncore proposing a new fee structure for transportation network companies like Uber and Lyft.

Minority Leader Bruce Tarr, who was frustrated last week that Democrats would attempt to use the budget to advance major policy initiatives in a lame-duck session, also filed his own plan to legalize sports betting.

Sport wagering is a potential revenue generator backed by Gov. Baker that is also being negotiated by a conference committee of the two branches as part of a larger economic development package. Sens. Brendan Crighton and Paul Feeney filed their own sports wagering amendment to the budget.

The amendment load averages out to 11.8 per senator compared to the 4.8 amendments-per-member average in the House last week, where the membership mashed its adopted amendments into four mega-amendments.