SUMMARY: This NPRM proposes to amend Federal Motor Vehicle Safety Standard (FMVSS) No. 213@ ????Child restraint systems@'' to adopt side impact performance requirements for all child restraint systems designed to seat children in a weight range that includes weights up to 18 kilograms (kg) (40 pounds (lb)). NHTSA is issuing this NPRM to ensure that child restraints provide a minimum level of protection in side impacts by effectively restraining the child@ preventing harmful head contact with an intruding vehicle door or child restraint structure@ and by attenuating crash forces to the child's head and chest. This NPRM is also issued toward fulfillment of a statutory mandate set forth in the ????Moving Ahead for Progress in the 21st Century Act'' (July 6@ 2012)@ directing the Secretary of Transportation to issue a final rule amending FMVSS No. 213 to improve the protection of children seated in child restraint systems during side impacts. DATES: Comments must be received on or before April 28@ 2014. Proposed compliance date: We propose that the compliance date for the amendments in this rulemaking action would be three years following the date of publication of the final rule in the Federal Register. Optional early compliance would be permitted.