Some numbers to consider when discussing a dedicated rail link to RDU:
If the 1-2% figure is accurate, 1 percent of 12 million is 120,000. Divide 120,000 by 365 and you get 329 passengers per day. (328.77) I realize that passenger count isn’t evenly divided over every day of the year, but we are discussing averages. Airlines tend to schedule flights during the 18 hour period between 06:00 and midnight. (Red-eyes, delayed flights, and my airline’s sadistic scheduling practices excluded.) So, on an hourly basis, the rail link will handle approximately 19 passengers per hour. (329 / 18 = 18.28) Remember that the 12 million passenger count at RDU is comprised of passengers departing AND arriving and the new figure per trip is 10 passengers per trip. (18.28 / 2 = 9.14)
So, a connection to RDU will supply, on average, 10 passengers per hour to the airport and 10 passengers per hour from the airport. Not included in this figure is the number of airport employees that would use the train.
Edit: The math I used was based on the 1% figure. Double the amount for 2% etc…