Adding passenger traffic does not necessarily require displacing freight traffic.
Here's a document that contains a map of current rail density: https://www.dot.ga.gov/InvestSmart/Freight/GeorgiaFreight/Ta...
Here's a document that contains a map of current rail density: https://www.dot.ga.gov/InvestSmart/Freight/GeorgiaFreight/Ta...
https://openrailwaymap.org/ shows (if you zoom in far enough) that at least some lines around Atlanta are only single track. https://www.trains.com/wp-content/uploads/2020/10/multi-trac... suggests most of them are.
It isn't a common issue in Russia or China (similar rail freight use to the USA). Double tracks means no waiting for opposing trains, and it's then straightforward to fit passenger trains, which stop at stations but go faster, between constant speed freight trains.
It does mean twice as much track must be maintained to a higher standard than freight-only track.