Section 503-B. Supplemental tax

1.  In addition to the taxes imposed by
  sections five hundred three and five hundred three-a  of  this  article,
  and  in addition to any other tax or fee imposed by law, there is hereby
  imposed on and after July first, nineteen hundred ninety a  supplemental
  tax,  for  the privilege of operating any vehicular unit upon the public
  highways of this state and the purpose of recompensing the state for the
  public expenditures  incurred  by  reason  of  the  operations  of  such
  vehicular  units  on the public highways of this state, equal to the tax
  imposed by section five hundred three of this article.
    2. The provisions concerning returns under section five  hundred  five
  of  this  article  shall be applicable to this section. The supplemental
  tax imposed by this section shall be  payable  to  the  commissioner  of
  taxation  and  finance  in full at the time the return is required to be
  filed.
    3. Except as otherwise provided in this section, all of the provisions
  of this article applicable to the tax imposed by  section  five  hundred
  three  of  this article shall apply with respect to the supplemental tax
  imposed by this section to the same extent as if it were imposed by such
  section five hundred three, insofar  as  such  provisions  can  be  made
  applicable  to  the  supplemental tax imposed by this section, with such
  modification as may  be  necessary  to  adapt  such  provisions  to  the
  supplemental tax imposed by this section.
    4. The provisions of this section shall not apply to (i) any vehicular
  unit  used  almost  exclusively to transport boltwood, logs, pulpwood or
  woodchips, and (ii)  any  vehicular  unit  used  almost  exclusively  to
  transport   raw,  unprocessed  milk  in  bulk,  provided,  however,  the
  provisions of clauses (i) and (ii) of this subdivision shall  not  apply
  to  any  carrier  or owner which operates more than three such vehicular
  units.
    5. Notwithstanding any other provision  of  this  article,  commencing
  January   first,   nineteen   hundred   ninety-nine   and  ending  March
  thirty-first, two thousand one, the  supplemental  tax  imposed  on  the
  privilege  of operating any motor vehicle unit shall be fifty percent of
  the tax imposed by section  five  hundred  three  of  this  article  and
  commencing  April  first, two thousand one, the supplemental tax imposed
  on the privilege of operating any motor  vehicle  unit  shall  be  forty
  percent  of  the  tax  imposed  by  section  five  hundred three of this
  article.