Trains

Until the freight railroads that host most passenger trains can be convinced that electrification is good for them -- and it definitely would be, looking at every other electrified mainline railway in the world is -- it sadly won't happen anytime soon under private ownership.

As an example, UP has been unusually hostile to overhead wires, claiming that they limit the vertical loading gauge to prevent double stacked containers. This is one reason why the farther part of the Caltrain service from San Francisco remains unelectrified, even after the publicly-owned rail section was successfully electrified to San Jose in 2024. Union Pacific refused to allow wires over their tracks down to Gilroy. This is an oddity for UP because they inherited the Southern Pacific's freight trackage rights on Caltrain's tracks, and do use those rights to service industrial customers on the way to San Francisco; I find their overhead wire argument to be unconvincing since if true, means that they're chosen to give up any possibility of serving these industrial customers with double stack consists forever after 2024.

The obvious locations would be steep, single track sections of the transcontinental lines through in the Western USA, where electric locomotives would have a pronounced climbing speed advantage that increases track capacity without having to build a second track.