I do not recommend trying to use the bypass on a Friday afternoon around 4pm. My personal name for that situation is "the circular parking lot".
I think 8pm is more likely to be okay than 4pm. Local radio station AM750 has traffic updates every ten minutes or so. Heads up, it has a lot of talk radio.
Some local trafic terms:
"The perimeter" - I-285, what is being referenced as a bypass, a rough circle shape around the city. The big semi's that aren't making local stops HAVE to be on the perimeter, so I285 has far more truck traffic than going straight thru town.
"Inner loop" - that's the part of the perimeter that goes clockwise. If you are coming down I-85 into Atlanta, you would be travelling the inner loop, along the northeast section of the perimeter, down to I-675, then to I-75. The exit from I-85 to I-285 is a mess called "
Spaghetti junction", and then you will likely get caught in a big traffic jam before Memorial drive if you are in afternoon rush hour.
"Outer loop" - the part of the perimeter that goes counter clockwise. I've avoided it during rush hour for a long time ... can't tell you about what the traffic pitfalls are these days.
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The connector" - that's the section of the interstate where I-75 & I-85 are joined. Here's where you find yourself with so many lanes heading in the same direction. It goes right through downtown.
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The Grady curve" - section of the connector close to Grady hospital ... this is just north of I-20. (I-20 runs east-west thru the city, south-ish end of downtown)
Rush hour - it really starts earlier on Fridays than other days of the week (so many people trying to beat rush hour that they just cause it to start earlier). Anything after 3 is risking traffic.
Good luck! I suggest saving your favorite Disney music for going thru Atlanta - at least you can distract yourself singing along to something fun