N.Y. Comp. Codes R. & Regs. tit. 21 § 1025.4
The limitations per vehicle, the exclusion, and the transportation without limitation of hazardous materials shall be in accordance with section 1025.27 of this Part and the related sections designated under the column "Tunnel regulation section." When two or more hazardous materials--with different quantity limitations as given in these regulations--are transported in the same vehicle at the same time, their combined weight shall not exceed the maximum allowed for the article having the higher weight limitation. The combined quantity of two or more articles having the same quantity limitations shall not exceed the quantity limitations for any such single item. Where contents (gallons) are known, it shall take precedence over gross weights (pounds) in limiting quantity per vehicle.
N.Y. Comp. Codes R. & Regs. Tit. 21 § 1025.4