While MARTA does not extend into Gwinnett, you can connect to the Gwinnett County Transit System from the Doraville Station. As the last stop on the MARTA gold line, the Doraville Station provides access to GCT Route 10 that travels up Buford Highway through Norcross, ending at the Gwinnett Transfer Center/Gwinnett Place Mall. The transfer center allows connections between all five local GCT routes and seven express routes.
There is also GRTA Express Route 410 that goes directly from the Lindbergh Station to Sugarloaf Mills. And GRTA Express Route 412 goes to Discovery Mills from the Civic Center and Arts Center Stations in addition to several other midtown stops in between.
GRTA Express is $3 one way or $5 roundtrip. GCT rates vary by route, from $2-$4. Transfers to/from MARTA are free and you can use your Breeze Card for Route 10.
A Gwinnett light rail system is on the list of projects that could be supported by a one-cent sales tax. Voters can support light rail expansion by voting in the Fall 2012 election.