Metro Transit on Tuesday will begin testing trains on the Metro Green Line Extension as construction on the project nears completion.

The extension, also known as the southwest light rail project, extends from downtown Minneapolis to Eden Prairie. Metro Transit says construction is about 85% finished, with the line expected to open to the public in 2027.

Until then, crews will need to conduct over 4,000 tests; the first test train will run west towards Eden Prairie, towed by a railcar mover at a speed of no more than 5 mph. Metro Transit says they'll be testing trains every day until the project opens. 

Other checks include testing the lights and warning signs at light rail crossings and verifying track alignment.

Metro Transit says they're starting a safety campaign to remind people to stay aware of the tracks.

The 14.5-mile track that connects St. Louis Park, Hopkins, Minnetonka and Eden Prairie to Minneapolis and St. Paul is the most expensive public works project in state history. The Metropolitan Council in 2011 projected it would cost $1.25 billion, but that sum has since more than doubled.