"We can learn much from terrorists' failures. Not only do they increase the total number of cases to be examined--there are far more terrorist failures than terrorist successes--they also provide insights into terrorist ambitions, clues to possible new directions in tactics and weapons, and details on how terrorist plots evolve, which are often more difficult to discern when an attack has succeeded and its perpetrators are dead or have fled. This report examines 13 terrorist plots against public surface transportation that were uncovered and foiled by authorities between 1997 and 2010 and two failed attempts to carry out attacks. Certainly, this is not the total universe of foiled or failed terrorist plots in these years. We selected these 15 on the basis of what is known about them and the accessibility of information. The report focuses on terrorist plots in the West. The United States, with seven plots, and the United Kingdom, with four plots, are probably overrepresented, but these two countries figure prominently as targets of terrorism. In addition, American and British officials have dealt with terrorist plots through publicized arrests and trials, which provide additional information. Although motive was not a criterion in the selection of the plots, all but one involve individuals or groups inspired by al Qaeda's ideology of violent global jihad against the West."