This rule would revise the definition of “tank vehicle” with respect to the applicability of the requirement for certain commercial driver’s license (CDL) holders to obtain an endorsement to operate tank vehicles. On May 9, 2011, FMCSA published the “Commercial Driver’s License Testing and Commercial Learner’s Permit Standards” final rule. As a result of the rulemaking, FMCSA received numerous petitions regarding the definition of a “tank vehicle” found in 49 CFR 383.5. The new definition of “tank vehicle” became effective on July 11, 2011, and required additional drivers to secure tank vehicle endorsements on their commercial learners’ permits (CLPs) and CDLs. This rulemaking responds to those petitions by seeking public comment on a proposed revision of the definition and the impacts this revised definition would have on the industry.