In early March, the U.S. DOT announced a $590 million rail grant to upgrade BNSF Railway tracks between Seattle and Portland, Ore. With this project, the agency has obligated $44.7 billion of the $48.1 billion in stimulus funds provided by the American Recovery and Reinvestment Act of 2009.

Most of the remaining money will be obligated under the administration's intercity passenger rail program. The agency has until September 2012 to allocate the remaining $3.4 billion.

To date, the DOT has reimbursed states $26.5 billion for stimulus-backed projects that have been completed.