§ 37. Municipal operation; revenue and accounts; operating and other funds. a. The aggregate amount of the gross receipts of moneys derived directly or indirectly from or in connection with the operation by the city of any road shall be known as the revenue thereof. Such revenue shall be derived from fares to be charged persons riding thereon; from rates to be charged for carrying property thereon; from rentals or fees to be charged for concessions or privileges thereon in connection therewith; from the sale of surplus power, and any other receipts from whatever source derived.

b. The board of transportation shall establish and maintain a system of accounts to show at all times the cost of the several classes of property used in operation and the sources of funds used in the acquisition of such property; the several classes of operating revenue and other income; maintenance expenses; interest, amortization, depreciation and all other charges against earnings. Such accounts shall be kept in accordance with the uniform system of accounts prescribed for railroads by the public service commission or other duly constituted authority and published in the City Record.

c. The revenue derived from all sources of income of any such road shall be deposited daily by the board in the name of the city in banks to be designated by the board of transportation and shall be held separate and apart from all other funds of the city as the operating fund for the payment therefrom of the expenses of operation, maintenance and repairs, and depreciation, interest and amortization charges. An accurate report of all moneys received shall be made daily to the comptroller of the city, who shall have power and whose duty it shall be to audit currently all the financial details of municipal operation, which audit shall not preclude examination of such account by any other properly constituted authority. An itemized report of the result of such municipal operation shall be filed each month by the board of transportation with the mayor and the board of estimate.

d. From the operating fund thus derived there shall be deducted the following charges in the order named and a separate accounting be made of each:

1. Operating expenses, exclusive of maintenance, including all expenses for personal service, materials and supplies used in operation.

2. Expense of maintenance and repairs of structures and equipment, which shall be the actual cost of keeping the structures and equipment in thoroughly good order and repair, and shall include the replacement of parts of construction and parts of equipment units, but shall not include the renewal or replacement of any complete units of property, as such units are defined and specified from time to time by the board of transportation for renewal or replacement from the capital reserve fund.

3. The amount of interest actually payable by the city and the proportionate annual contributions to sinking fund or other funds to amortize and retire the bonds, corporate stock or other evidence of indebtedness issued by the city on account of any road.

4. Contributions to a depreciation fund for replacement or renewal of worn-out, obsolete or inadequate units of structures or equipment, of the amount the board of transportation shall determine is the estimated net loss of value, after maintenance has been applied, of such complete units of property, with due provision for obsolescence or inadequacy of such units.

e. The deduction for expenses of operation and maintenance shall be made currently as required, and the deductions for depreciation, interest and amortization installments shall be made after the close of operations each month and shall be the monthly proportion of the annual amount required for such purposes.

f. In addition to the principal operating fund in which all the revenue shall be deposited as above provided, there shall be established and maintained in the custody of the comptroller a separate fund and bank account, to be designated as the capital reserve fund, to which shall actually be transferred the amounts deducted from revenue on account of interest, amortization and depreciation. Any surplus or balance which shall accrue from the revenue at the end of the fiscal year, in excess of an amount equal to the average cost of operation and maintenance for one month during such fiscal year, shall also be paid into such capital reserve fund. Such fund shall be available for disbursement in the same manner as the principal operating fund for the following purposes in the order specified:

1. Interest payable by the city on account of bonds or other evidences of indebtedness issued, and contributions to sinking funds established for the retirement thereof;

2. Amounts necessary for renewals or replacements on account of depreciation and obsolescence. Any surplus accruing in the capital reserve fund over and above the amounts disbursed for the purposes specified shall be retained in such fund and may be expended only for the support, installation or extension of such transportation facilities. All interest earnings of such fund shall be added to the fund. The comptroller shall make all payments out of the capital reserve fund, and shall report quarterly to the board of estimate the condition of the fund, itemized as to the amount on hand for interest, amortization of bonds or other evidences of indebtedness, depreciation and surplus, and shall keep the account of the fund so subdivided. g. Payments or withdrawals of moneys from the operating fund and the capital reserve fund shall be made by checks drawn and signed by the comptroller upon vouchers certified by a member or an officer of the board of transportation, duly authorized by resolution of such board, except that payments of interest, contributions to sinking funds and on account of retirement of bonds or other evidences of indebtedness shall be made by the comptroller upon his own initiative as such payments become due and payable, but a memorandum of such payments shall be transmitted by the comptroller to the board of transportation for entry in the accounts thereof. The comptroller from time to time shall inform the board of transportation in writing as to the amount to be periodically deducted from revenue on account of interest and amortization requirements, and the monthly charges and vouchers for such amounts shall be made in accordance with such devices.