What is light-rail transit? Purple Line is 89% complete in Maryland

Maryland's Purple Line — at 89% completion — is heading for the final stretches of construction that began nearly 10 years ago.

It will connect to four stations in the Washington Metropolitan Area Transit Authority's Metro system, but the Purple Line differs from the Metro's heavy-rail line.

Here's what to know about light-rail systems and how the Purple Line will operate.

What is the Purple Line?

"The Purple Line is a light rail line powered by an overhead catenary system that can operate on the surface of roadways where vehicles and pedestrians can easily cross over its tracks," according to the Maryland Department of Transportation.

This means the Purple Line will run alongside traffic or in a separate right-of-way, whereas the Metro is separated from cars and pedestrians. Only short sections of the new line will be elevated or underground.

Officials describe light rail transit as "an electric railway system characterized by its ability to operate single cars or short trains along rights-of-way at ground level, on aerial structures and in tunnels."

The Purple Line is projected for a winter 2027 launch and says it will operate trains in both directions every 7.5 minutes during peak periods and every 10-12 minutes in off-peak hours. Officials project daily ridership of about 60,000 passengers.

Each 140-foot-long train can carry up to 431 passengers, including seating for 80.

Crews completed laying tracks in Prince George's County last year, and the lines remain under construction in parts of Montgomery County.

The Purple Line is the first light-rail system in the DMV, but it's not the first in Maryland. The Baltimore Light RailLink has been in operation since 1992.

Dozens of other major cities, including Boston, Dallas and Los Angeles, also use light-rail transit, which are often used to connect urban areas to surrounding suburbs.

This is also the objective for the Purple Line, with officials saying it will connect communities and improve access through DC's Maryland suburbs.