A bill filed by Dorchester lawmaker Evandro Carvalho last week would direct the MBTA to launch a two-year “pilot service evaluation” of the Fairmount Line. The legislation would advance a longtime goal of transit equity advocates: changing the existing commuter rail line to “an urban Rapid Transit line under the Indigo Line brand” that would mirror service levels on the T’s Red, Orange, and Blue lines.

Carvalho wants the MBTA and Keolis, the commuter rail company, to devote “no less than three train-sets” to the line— each with no more than three coaches to decrease stoppage time— and to wrap them in newly-designed Indigo markings. The bill would also require that trains run every 15 minutes during peak times, and no longer than every 30 minutes off-peak, and allow riders to use Charlie Cards and other passes used on subway lines.

The pilot would also include a robust marketing campaign aimed at getting more people to use the line, which Carvalho envisions as a solution to the “transit desert” that confronts many of his constituents in Dorchester and Mattapan.

The bill calls for the state Department of Transportation, the MBTA, and Keolis to work in partnership to “assess the impact of adequate service levels” using revised ridership data within 180 days of the bill’s adoption— if it becomes law.