I’ve been asking that for a while.
The Simple Answer
Don’t rely on MARTA to provide you a restroom. Use the facilities before you leave and when you get there.
The More Complicated Answer
MARTA is not a long-haul or commuter rail service. There are no restrooms on the trains or on the buses.
According to this MARTA page, there are 13 stations with restrooms, but most are not available to the public unless you find an attendant to let you in. Lindbergh Center has a fancy electronic admission system on the restrooms, but it’s been closed the last 4 times I’ve tried to use it. There are restrooms on the main concourse at Five Points with signs that tell you to go find an attendant. Each time I’ve been by there, the restroom doors have been wide open, though, so an attendant wasn’t needed.
Several station restrooms have been closed recently, and the MARTA alert has said to use Five Points. That is probably the best option no matter where you’re at on the train. If you’ve on the Red or Gold Line south of Five Points, getting off at the airport might be the best option. The restrooms there are going to be cleaner and nicer than any on the MARTA system. Of course, you’ll have to pay for another trip since those restrooms are outside of the fare gates.
If you need to go while riding a bus, you’re on your own! Get off near a QT or Racetrac.
The Details
If you’ve a frequent user of MARTA, keep track of places near stations or popular bus stops where a restroom is available. Malls, a big box hardware store, a coffee shop where you can order something. You’ll thank yourself when you’ve stuck out there in the wilds of Atlanta and the urge strikes.
If you can get into a MARTA restroom, I wouldn’t expect too much…if you know what I mean.
Try to minimize wait times when transferring to avoid the dance of shame. Check bus schedules with the Transit App to make sure you’re not waiting for 30 minutes at a station with no facilities.