From the Office of the Inspector General. With $54 billion in annual expenditures, it's no wonder they uncover so much fraud:

Contract and Grant Fraud Reading Room

One of the strategic goals of the U.S. Department of Transportation (DOT) is to "Advance America's economic growth and competitiveness domestically and internationally through efficient and flexible transportation." In support of this goal, DOT spends more than $54 billion a year on transportation related projects in virtually every community in the nation.

House and Senate conferees are currently working on a six-year renewal of the Transportation Equity Act (TEA-21)with proposed spending authority of $299 billion to rebuild the Nation's surface transportation infrastructure. Another program, The Aviation Investment and Reform Act (AIR-21) will commit an additional $40 billion for modernization and stability of our nation's aviation systems. To protect the integrity of these and other transportation-related programs against fraud, waste, and abuse, the Office of Inspector General (OIG), the Department's criminal investigative element, has made investigating contract and grant fraud one of its top priorities.