Just to note, this doesn't apply to every journey, only the really long distance ones.
Amtrak is still the more climate-friendly option for the vast majority of travelers, who on average travel 300 to 400 miles, said Olivia Irvin, a spokeswoman for the rail company. (That is, not many people are crazy enough to go cross-country by train.) A 2022 Department of Transportation study found that traveling by train from Los Angeles to San Diego generated less than half the emissions, per passenger, of flying, or driving. For Boston to New York, an electrified route, taking the train generated less than a fifth the emissions of flying or driving.
Walkability generally means higher density and higher density means lower cost. The only reason why walkable places are generally less affordable right now is that they are scarce. If everywhere was walkable that wouldn't be a problem.