Mangler: The whole point of the farthest-flung MARTA stations was to grab commuters off the highways who would rather ride a predictable train into town instead of a bad-to-worse ITP trip. If you have only one (train) every 15 minutes, you're not going to make a lot of commuters want to trade the wait on the highway for the wait on the platform. Offering frequent trains at rush hour is what will grab those drivers. What about shortening some of the trains but having them run more often? I see so many six- to eight-car trains with maybe 50 people on the whole thing. What if that was a two-car train, then in 6 to 10 minutes, another two-car train? Would that lead to efficiency and increase incentive to jump on? It doesn't necessarily have to save all that much time over driving to grab stressed-out commuters who don't have jobs requiring them to have their cars with them all day, but waiting on the platform for 15 to 20 minutes does sting.
Don: Let's see, in order to increase frequency, you have to budget more train crews. In order to budget more train crews, you need more money. Outside of the fact that increased frequency will induce more fare-paying riders. How about zoned fares? How about higher peak-hour fares? A ride from Doraville or North Springs to the airport has a heck of a lot more value than a Five Points-to-Arts Center (and Atlantic Station) shopping trip.