House committee substitute makes the following changes to 1st edition. Amends proposed GS 20-37.16(c2) by adding language providing that a commercial drivers license that contains an H or X endorsement, as defined, expires on the date of expiration of the licensee's security threat assessment conducted by the Transportation Security Administration of the United States Department of Homeland Security. Provides that when the commercial drivers license also contains an S endorsement and the licensee is certified to drive a school bus in North Carolina, the commercial drivers license expires as provided in GS 20-7(f). Changes the effective date to July 1, 2012 (previously December 1, 2011), and applies to endorsements issued for commercial drivers licenses on or after that date.