As often the case, much of the market potential is based upon both the location of population centers and population densities (number of people per square mile or other geographically defined region). To truly answer this question, passenger rail needs to be discussed within its three distinct distance categories: commuter rail (generally 50 miles or less), short-haul intercity rail (generally between 50 and 300 miles), and long-haul intercity rail (generally greater than 300 miles). We will also look at some non-geographic factors that can affect rail travel as well.
Commuter rail caters to the daily traveler who is using the train as the primary mode of transportation, to and from work on a daily basis. Two examples of commuter rail operations in the United States include Caltrain (service between San Francisco and San Jose, California), and Metra (service between downtown Chicago, Illinois and its respective northern, western and southern suburbs). Commuter trains generally have basic seating configurations (no reclining seats), and very little in the way of lavatories and food concessions on the train. Commuter trains are found in areas with a relatively dense network of suburb cities (often in sequence) and a large job destination city (i.e. Chicago). These types of trains generally make stops frequently, every five miles or so.
Short-haul intercity rail caters to both the daily commuter and the recreational rider who is taking the train to visit friends up towards 300 miles away. Short-haul intercity trains generally have more spacious seating configurations than found on commuter trains, and will often have basic lavatory facilities and food concessions (snack stand in one of the passenger cars).
Three examples of short-haul intercity passenger rail in the United States include Amtrak's Northeast Corridor (service between Washington D.C. and Boston), Amtrak's San Joaquin Corridor (service between Oakland and Bakersfield, California with bus connections to Los Angeles and Las Vegas), and Amtrak's Cascades Corridor (service between Eugene, Oregon and Vancouver, British Columbia). These types of trains will generally make stops every 20 to 50 miles, or stop in towns of reasonable population size.
Long-haul intercity rail caters to the recreational traveler who is taking the train a distance of more than 300 miles, to visit friends or where on-time performance is important but not critical. Long-haul intercity trains generally have the most spacious seating configurations (reclining seats with foot rests and greater legroom than found in coach class on airplanes). These trains also include food concessions (both a snack car and often a dining car offering full meal service), and sleeping cars for those who would like more spacious accommodations for overnight travel.
Three examples of long-haul passenger train in the United States include Amtrak's Coast Starlight (service between Seattle, Washington and Los Angeles), Amtrak's Southwest Chief (service between Los Angeles and Chicago), and Amtrak's Cardinal (service between Chicago and Washington D.C.). These types of trains will generally make stops every 50 to 80 miles, or stop in towns of reasonable population size.