No motor vehicle impounded pursuant to an arrest under MGL c.
90, § 21, for operating under the influence of intoxicating
liquor, marihuana or narcotic drugs or depressant or stimulant substances,
all as defined in MGL c. 94C, § 1, or under the influence
of vapors of glue, or other substances set forth in said MGL c. 90,
§ 21, may be released prior to the passing of 12 hours following
arrest.