Book excerpt: U.S. transportation systems and the estimated 4,000 transportation facilities move over 30 million tons of freight and provide an estimated 1.1 billion passenger trips each day. Since 2001 the Transp. Security Admin. (TSA) has protected these systems and facilities from terrorist attack. One program TSA utilizes is the Transportation Worker Identification Credential (TWIC) program, through which a common credential is being developed for transportation workers with access to secure areas. Ultimately planned for all transportation sectors, TSA is initially focusing the TWIC program on the maritime sector. This testimony discusses: the progress made in implementing the TWIC program; and some of the remaining program challenges.