Mass. Gen. Laws ch. 161B § 26
The regional transit authorities shall establish a stabilization fund into which the authorities shall deposit revenues in excess of expenditures. Said stabilization fund shall have a fund balance no greater than 15% of total revenues for all regional transit authorities for the fiscal year most recently ended. Monies from said fund shall be subject to appropriation and used for capital improvements and expenditures, to offset the unforeseen and dramatic loss of revenues within a fiscal year, and to pay current expenses after implementing all efficiencies and savings possible. The authorities may not assume draws from said stabilization fund in preparing their annual budgets. In the event that an authority requires a draw from said fund, it shall file with the secretary of administration and finance, secretary of transportation and construction, joint committee on transportation and the house and senate committees on ways and means a financial plan that projects to produce in the following fiscal year an excess of revenues over expenses, all measures taken to implement efficiencies and savings, the amount necessary to offset operating losses, and any other information that said secretaries or committees may require.
Mass. Gen. Laws ch. 161B, § 26