Mass. Gen. Laws ch. 161A § 19
The authority shall establish a Stabilization Fund into which it shall deposit revenues in excess of expenses pursuant to section 21 until the fund balance is equal to or greater than 5 per cent of total revenues of the fiscal year most recently ended. The authority may draw funds from the Stabilization Fund only in the event that, after implementing all efficiencies and savings possible, annual revenues are projected to be less than annual expenses, or if it has insufficient funds on-hand to pay current expenses. The authority may not assume draws from the Stabilization Fund in preparing its budget pursuant to section 20. In the event the authority draws funds from the Stabilization Fund, it shall file with the secretary of administration and finance, the secretary of transportation and construction, the 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.
The authority shall also establish a Fare Stability Fund, into which it shall deposit revenues in excess of expenses pursuant to section 21. The authority may assume draws from the Fare Stability Fund in preparing its budget pursuant to section 20. Funds in said Fare Stability Fund shall be utilized within five fiscal years after being deposited.
Mass. Gen. Laws ch. 161A, § 19