All the trains I have been on in California burn diesel fuel, including the one I commute on every day. Caltrain down the peninsula burns 10 million dollars in fossil fuels a year. I would hope we could convert already heavily used rail corridors to electric sometime in my lifetime.

http://www.caltrain.com/Assets/__Agendas+and+Minutes/JPB/Boa...

It's in progress:

http://www.caltrain.com/projectsplans/CaltrainModernization/...

As long as you're still alive in 2022 (and there are no more funding issues caused by the tie-in to HSR), it will happen within your lifetime.

Should have happened a decade or more ago, but Caltrain is the underfunded stepchild with the bulk of transit dollars going to BART.

Of course, BARTs eBART expansion is diesel, not electric.

At least it's standard gauge rail, so that's a plus.

Caltrain is currently in a project to convert to electric, as others have noted.

It's not particularly feasible in the US to convert freight-dominated lines to electric. Modern freight generally uses the double-stacked container as its loading gauge, and electric catenaries would sit several feet below the top of the double-stack container--the standard height for a bilevel in the US is 14.5 ft, but the double-stacked container runs to 20 ft.

This picture shows a double stack container under electric catenary, so it's possible. The cost would be high for the length of tank involved. Electrification's non-green advantage is faster acceleration, which is easy to justify on busy passenger lines as you get faster journeys and potentially more trains, but not important for freight.

http://testplant.blogspot.dk/2013/09/electrification-clearan...

If you think longer-term, electric trains are realistic. If batteries are cheaper than Diesel, you could just put 2x20ft container at the front with batteries. They can be swapped en-route and used as battery storage when not in use. As far as I know, most newer freight trains are diesel-electric anyway so not sure if you couldn't just feed the electric engine directly from a battery without buying new engines.

Currently not feasible because of high battery prices but realistic in 1-2 decades. And losses are lower than for electrified rail.

Busy routes are still better electrified but the huge US freight rail network would likely be cheaper to convert that way.

Could they use a third rail system? https://en.wikipedia.org/wiki/Third_rail

Not really. Freight lines are usually built at-grade and occasionally intersect city streets. Caltrain tracks included. Some of the Caltrain stations doesn't even have elevated platforms.

It would be... unpopular... to have an electrified third rail, at ground level, that you have to step directly over at a station or running directly through a city street. Somebody would surely trip on it or it could get touched by a little kid.

Third rail systems are usually only used when the tracks are physically inaccessible to passengers or other pedestrians.

Plenty of third rail in the south of England, they just stop the rail before level crossings and start it again afterwards.

Caltrain is being electrified right now and due to be done in six years, and of course CA High Speed Rail is going to be electric.