"The nation's air, land, and marine transportation systems are designed for accessibility and efficiency, two characteristics that make them highly vulnerable to terrorist attack. While hardening the transportation sector from terrorist attack is difficult, measures can be taken to deter terrorists. The dilemma facing Congress is how best to construct and finance a system of deterrence, protection, and response that effectively reduces the possibility and consequences of another terrorist attack without unduly interfering with travel, commerce, and civil liberties. In the 110th Congress, aviation, rail, and transit security were a major focus of congressional activity. At the end of July 2007, the House and Senate passed a conference agreement on H.R. 1 (H.Rept. 110-259) that was signed into law on August 3, 2007 as the Implementing Recommendations of the 9/11 Commission Act of 2007 (P.L. 110-53). The act contains numerous provisions related to air, rail, and cargo security."
CRS Report for Congress, RL33512