Why not promote train travel for both: highly traveled routes where service already exists and rural areas that need service? Plus logical corridors where train service doesn't exist?
For example, I am thrilled that I can go out of PHL on a train to many places, and I tell that to anyone who will listen, but that doesn't mean I don't want to advocate for a train to go to Northeast PA or from Springfield to Boston (which I think was being planned? It's long overdue, though.)
I think the best place to start is with small businesses--whenever I get a tourist brochure from an area without train service, I write back and tell them how much I would love to visit their lovely area, but I only travel by train and so am able to spend my tourist dollars only in towns I can get to by train. If enough of us did this, it might finally start to sink in and encourage those towns to pursue train service.
There are other small ways to advocate--whenever someone asks how I got to wherever, and they say "Did you fly or drive?," I very politely say, "I came by train--it's the only way I travel." At which point, they always say, "I didn't know the train went to [town name]," and I describe the train service to them.
So I think a national day is a good idea, but I agree somewhat with Philly Amtrak Fan--highlighting our weakest points won't help. I think a general ad campaign might be better (look at how excited everyone--well almost everyone--is about Brightline)--they've done a good job of feeding us tantalizing tidbits while we wait for the actual service to start. And even non-train people know about it.
Sorry this is a mind dump, but it's the advocacy ideas that have been kicking around in my brain for a while. And one more--my favorite--is to compliment Millennials on how smart they are to take the train
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