So you'll electrify the Coast Strarlight and the Pacific Surfliner right? Right?
Moving 1% of car trips in California to any other mode would (almost certainly) reduce emissions more than eliminating emissions from trains.
Better plan: Convert half the lanes on those giant freeways to HOV only and provide a website/app where people can find carpool partners (ID verified with your driver's licence). First week would be chaos, but you would get a big shift within a month that benefits everyone. Cost would be trivial.
I agree with you, but the main train lines to be electrified is still something that can do good for the environment.
