N.J. Stat. § 54:29A-14
For the purpose of this article, net railway operating income shall be computed as total railway operating revenues from all sources, including any revenue whatever derived directly or indirectly from property which is used for railroad purposes, less costs of railroad maintenance, operation, depreciation and amortization, railway tax accruals, uncollectible railway revenues, rentals (both debits and credits) for equipment leased for less than 1 year or interchanged, and joint facility rents (both debits and credits); provided, however, that amounts paid by the State of New Jersey or any county or municipality, or any agency, authority or subdivision thereof, pursuant to contracts for passenger service, shall not be included as such operating revenues. Deductions from operating revenues for depreciation, additions and betterments, and compensation for personal services shall be subject to regulation by the commissioner, as to reasonableness of amount and appropriateness of accounting distribution.
Depreciation and amortization charges shall in no instance, however, exceed the amounts permitted by the Interstate Commerce Commission in determining the net railway operating income of the railroad for the year under consideration.
For the purpose of determining the measure of the tax imposed by this act, net railway operating income of each system, and of each railroad not part of a system, shall be allocated to this State in the proportion that the number of miles of all track over which the railroad or system operates in this State bears to the total number of miles of all track over which it operates.
N.J.S. § 54:29A-14