The difference between doing it at age 30 or 40 or 50 or 60 and doing it after retirement is that today, I don't care when I get home.  I can always carry the cell phone and lap top to keep in touch.   I can deposit enough money in advance with the power company, the water company, the sewer authority, etc., so that I'm not delinquent.   I can call American Express from anywhere in the world and tell them to take the money out of my bank account.  When I was working, I had to be back on a certain Monday.   It took me three weeks tops to cross the USA and back.   Some days were hell on wheels.  Can you picture Palo Alto to Salt Lake City in one day?
That's nothing.   The longest was leaving a friend's house in Grand Island, Nebraska after breakfast on Saturday and pulling into my drive on Sunday afternoon. My wife shared the driving ... she drove an hour while I drove two or three.   

Well today, I will take four to six weeks to cross the USA and return home.   There is always a new road to drive.

In Europe?  Well, there I am restricted by needing to have a flight home.  But in between arrival and departure I still simply let a trip evolve one day at a time.   I had one friend who used to go to Europe every summer ... he had an itinerary mapped out in advance covering every single hour of every day including when he do his wash.   I could not travel with a man like that.   Wash?   Oh, there's a laundromat (or Washerie in Germany), guess I'll stop and do it now.   I remember coming across Canada.  Got near to the US border, had a pocket jammed full of US quarters, so I crossed the border and did my launder, and then went back into Canada.   Can you imagine explaining that to the customs people when they ask their usually litany of questions about where are you going `especially when the same man saw you two hours earlier coming south?

Jim, if you want to see those new light rail systems, you have to get in your car and do it.   

I would pick the good ones first so as to not become disillusioned.   You don't want to see the useless ones first and we have created some of them.  

I am attaching at the bottom of this e-mail, my list of USA and Canadian light rail and subway lines.   The second file is the passenger counts for the rail systems.    Both are Excel 2004 documents and not the newest version of Excel so you should be able to read.