subject to clause (2) of subsection (a), except as follows: (1) No conveyance used by any person as a common carrier in the transaction of business as a common carrier shall be forfeited unless it shall appear that the owner or other person in charge of such conveyance was a consenting party or privy to a violation of sections 4B, 6, 7, 8, 12, 13 or 53A;(2) No conveyance shall be forfeited by rea