As I'm sure you're aware, the official chattanooga to atlanta route goes way out of it's way to hit the silver comet, which is unnecessary given the multiple North/South roads that are safe to ride down through Adairsville, Cassville, Cartersville, etc.

I just did Tunnel Hill to Adairsville back in June and did a huge chunk on 136. It's flat and had low traffic with a decent shoulder for most of it. Not sure if this would be a good option during the week but it was fine on a Saturday late morning/early AM. Although really, this far north any of the parallel roads would be just fine as well. I just wanted a flat option as I was climbing some of the peaks in John's Mountain wildlife area.

Here's the route I rode:
https://ridewithgps.com/routes/17092249

Here's a good alternate using Pocket Road instead of 136:
https://ridewithgps.com/routes/17092275

And just because I like to share here's a link to my ride and ride report.
https://www.strava.com/activities/613204739
https://drandalls.wordpress.com/2016.../sugar-valley/


ETA: Oh man I've spent a lot of time baking in the summer sun on your route from Cartersville to Dobbins. That's good ridin'