Chicago Metra never goes any more than 50 miles away. And even that they go sparingly, not a full time service, only during rush hours and very few at off peak times. To Kenosha.
Metra runs where it does because that is the extent of the Regional Transit Authority (except for Kenosha). To go any further would require more Illinois counties to join the RTA.
I cant see any average American commuting from 90 miles or further away.
Define "average American." I'm sure the "average" American probably doesn't commute by rail at all, yet we still have commuter trains. So...what's your point?
The issue isn't whether you'll get 50% of a population (or whatever arbitrary number you or anyone else may come up with) to use a service. It's whether or not you'll get enough usage for it to be reasonably effective given its cost (and that is something that will always be subject to debate).
I ask this to see if MBTA extension to Springfield is feasible.
The real issue isn't about distance (pilots and flight attendants, for example, may live a thousand miles from where they work), or necessarily even travel time (there are people in some cities with ****-poor public transit who have to take two or three buses and ride an hour and a half each way to get to/from work, and are traveling less than 10 or 15 miles each way), but rather where the population lives, and where people work.
Take a look at California, and you'll see people that commute long distances each day to/from work, because housing in certain cities tends to be so expensive, that the people that work there couldn't possibly afford to live there.
So, the question is, do enough people live in Springfield and work in Boston (or vice versa) to make it worthwhile to have regular commuter service between the two cities? Do enough people make that commute on a daily basis that would benefit from having a few trains in each rush hour go back and forth?
The issue of what is "commuter" is not one that is defined by distance.