People will stop driving if you give them an incentive to stop driving. That incentive could be quicker commutes, not having to wait in traffic, not having to pay for parking, etc. But there has to be some incentive.
The whole issue of how incentives drive human behaviors is one of the main premises behind the Freakonomics books.
You cannot just "build it and they will come." That mentality has been shown to fail. People like driving their cars. They see it (in part) as part of who they are and link it to a sense of personal freedom, among other things.
Cities like Boston, DC, SF, NYC, etc are places where it really, really sucks to drive. And the cost of parking is prohibitive. And it really, really sucks to commute (though if I understand from the beginning of this story, this is article was not really about metro areas and commuting as such). But in places like that, riding a train is a no-brainer.
I think we all know that driving in Jacksonville during rush hour can suck pretty bad, but it's rarely as bad as it is in those other places.
You can build railways, but you need to address the issue of changing peoples' perceptions and working to change peoples' behaviors as well. And you need to offer some incentive to use the railway. And as long as Downtown Jax is basically a ghost town, you need to understand that ridership will be very low for a long time, but commit to seeing the project through to completion (and beyond). And you need to make sure that a real Downtown redevelopment project is part of the overall plan, so we actually start getting businesses back downtown. I think that last place is the place to start. But it cannot be ignored.