Tax Law, § 210(3)(a)(2)

Receipts by the taxpayer from transportation by omnibus may be allocated to New York State by the percentage that the mileage within New York State bears to the total mileage within and without New York State, or by the percentage that the time operated within New York State bears to the total time operated within and without New York State or by any other method approved by the Tax Commission. Mileage or time operated while an omnibus is engaged in school bus operations must be disregarded in computing the percentage.