Every day, 1,800 passengers head to the rail station next to BWI Thurgood Marshall Airport.

Every day, they board more than 40 trains headed for Washington, Baltimore, Philadelphia, New York and destinations all along the Northeast corridor. It's the 15th busiest station in the Amtrak network.

Now, the Maryland Department of Transportation wants to explore the idea of doubling its size and applied last week for a $10 million federal grant for a detailed engineering study.

"It's one of the busiest stations on the Penn Line," said Jack Cahalan, department spokesman. "As we try to provide more transit options for people...