At least with my card (US BOA) the process seems more real time. The charges appear immediately as "pending" and then become firm charges in no more than a day (except for held charges like hotels and car rental). As for Amtrak, I had the opportunity to book and then immediately cancel a reservation when I accidentally entered the wrong date. The charge appeared first pending and then firm. A second credit-back transaction appeared a day later for the full amount of the original reservation.