(a) The tax for each such motor vehicle shall be computed by multiplying the number of miles operated on the public highways in this state by the appropriate tax rate as it appears in the gross weight method table entitled "laden miles" set forth in paragraph (b) of this subdivision for the gross weight of the motor vehicle.

(b) Gross Weight Method Laden Miles Gross Weight of Vehicle Tax Rate

(c) Provided, however, when a motor vehicle is operated without any load or cargo, either alone or when it is drawing an unloaded trailer, semi-trailer, dolly or other device, the carrier shall in lieu of computing the tax by the gross weight method table entitled "laden miles" compute the tax by multiplying the number of miles operated under such conditions by the appropriate tax rate entitled "unladen miles" for tractors set forth in this paragraph, if the vehicular unit is propelled by a tractor, and by the appropriate tax rate entitled "unladen miles" for trucks set forth in this paragraph, if the vehicular unit is propelled by a truck. Such tax rate shall be determined by the unloaded weight of the tractor if the motor vehicle is a tractor and, in all other cases, by the combined unloaded weight of any such motor vehicle plus the unloaded weight of the heaviest trailer, semi-trailer, dolly or other device to be drawn by such motor vehicle (determined in a manner similar to the methods for determining the unloaded weight of a motor vehicle) when the motor vehicle is operated under such conditions. Provided further, however, when an unloaded tractor is being operated alone, the carrier shall compute the tax by multiplying the mileage operated under such conditions by the appropriate tax rate for trucks set forth in this paragraph determined at the unloaded weight of the tractor. Gross Weight Method Unladen Miles Tractors Tax Rate Unloaded Weight

(d) Provided, however, for purposes of determining the applicable rates of tax under this subdivision, for those miles when a truck does not draw a trailer, semi-trailer, dolly or other device, the gross weight and unloaded weight of the truck shall be determined without regard to the weight of any trailer, semi-trailer, dolly or other device drawn at other times by the truck or the weight of any load carried by any such trailer, semi-trailer, dolly or other device. 2. In lieu of basing the tax on the gross weight and mileage of each vehicular unit consisting of a combination of motor vehicle and trailer operated as a unit, any carrier operating more than one such vehicular unit may elect in his return to base the tax on (i) the gross weight of its heaviest laden motor vehicle and the number of laden miles all of its motor vehicles are operated on the public highways of this state under such condition by the tax rate entitled "laden miles" set forth in paragraph (b) of subdivision one of this section plus (ii) the unloaded weight of its heaviest unladen tractor, if the vehicular unit is propelled by a tractor and in all other cases, by the combined unloaded weight of the motor vehicle plus the unloaded weight of the heaviest trailer, semi-trailer, dolly or other device to be drawn by such motor vehicle (determined in a manner similar to the method for determining the unloaded weight of a motor vehicle) and the number of unladen miles all of its motor vehicles are operated on the public highways of this state under such conditions by the tax rate entitled "unladen miles" set forth in paragraph (c) of subdivision one of this section for the tractor or truck, as the case may be. Provided, however, when an unloaded tractor is being operated alone, the carrier in lieu of the computation required by clause (ii) of this subdivision for such mileage shall compute the tax for the mileage operated under such conditions by multiplying the appropriate tax rate for trucks set forth in such paragraph determined at the unloaded weight of the tractor. Such election may be made with respect to each return filed by a carrier and shall apply to all such motor vehicles required to be included in a return of the carrier during the taxable period covered thereby. Such election shall be irrevocable with respect to the taxable period for which the return is filed. 3. In lieu of computing the tax on the basis provided in the preceding subdivisions, any carrier may elect to compute the tax on the basis of the unloaded weight of each motor vehicle and the number of miles it is operated on the public highways in this state. The tax computed for each such motor vehicle shall be computed by multiplying the number of miles operated on the public highways in this state by the appropriate tax rate in the following tables: Tax Rate Unloaded Weight of Truck