BALTIMORE—Six years ago, Melissa Malcolm gave up on the commuter train to Washington, D.C., after breakdowns twice left her stranded in hot railcars. Now, on a good day, she makes the 40-mile drive in about an hour and a half.

“It’s horrific,” said the 35-year-old, who directs national sales and field marketing at the Milk Processor Education Program.

So Ms. Malcolm is rooting for an ambitious bid to build a high-speed train line that would zip riders between Baltimore and Washington in about 15 minutes.

The still-distant dream of maglev—short for magnetic levitation—is inching ahead. Maryland officials announced last week a $2 million pledge from the government of Japan, where a version of the technology was developed, for a feasibility study. Last fall, the U.S. Transportation Department awarded a $28 million grant for environmental and engineering studies.

Northeast Maglev, the company promoting the effort, says the roughly 40-mile line could open in about a decade at a cost “somewhat north” of $10 billion, with the Japanese government covering a major portion. The technology uses magnetic forces to accelerate trains to speeds of more than 300 miles an hour as they hover inches off the ground.