Sad. I wish we could restore and modernize train service all over California. The graded space for the rails already exists, and that is arguably the hardest part of building a railway.
A similar project is underway in Ireland [0], where they decommissioned a large number of former passenger lines in the 1970s, and are now spending millions of euros converting them to "greenways". To give one example, the Youghal to Midleton "greenway" replaced a former commuter rail line connecting commuter towns to Cork City. Every day, thousands of people drive between those towns, resulting in traffic jams and unnecessary CO2 emissions. Re-opening the train line would be a no brainer, they have more commuters today than ever before. Instead, residents now have the option of cycling or walking along a desolate trail through a bog.
[0] https://www.corkcoco.ie/en/resident/greenways/midleton-to-yo...
So a key question is: are there a lot of people trying to move between SF and Humboldt Bay? Does the carbon from transportation along this line warrant the renovation of the rail line (which itself produces emissions)? And if you build a train and no one rides that train, then that's probably even worse for emissions.
> California has enough hiking trails
This is pretty subjective. You can probably get rid of several of America's national parks and say "yeah we have enough national parks".
Also, realistically, how many people are going to actually travel the 300 mile trail on foot/bike?
Connstruction is easy. It's the multi-stakeholder approval process that's fiendishly difficult. You still have to go through that even if the graded space is already in place. Lots of stakeholders trying to get what's theirs, whether rent-seeking or stopping the work altogether. https://www.nytimes.com/2022/10/09/us/california-high-speed-...
It's way easier to build this sort of thing new than it is to refurbish it and certify it as safe. Less costly, too.
You're going to lay down new rail either way, and that's what you'll have to certify as safe, so it's not really any different. I'm just saying there's less crap you have to dig up if your starting point is an already-cleared 300 mile stretch rather than 300 miles of raw nature.