I think most of SFO's staff is back in school. Bsides that, it IS the end of the season, the crowds are lighter. Lets not for get everyone's favorite little insentive, $$$$! Less trains per hour = less wear and tear on the tracks = less repair = less staffing = more profits.
Even though 20-30 minute wait for the Villain doesn't sound bad, I know, it could be less. Knott's is currently running a 1 train operation on Ghostrider on weekdays due to light crowds. The crappy part is that they own 3 trains, one is always under the station in the "garage" and the other 2 travel the circut. Well, how do they run only one train? Simple, one of them is loaded, the other runs empty ALL DAY LONG! Here is the kicker, every time the empty train pulls into the station, ride ops still have to check restraints, and dispatch the train. Half of the time, the empty train has not yet been dispatched when the loaded train arrives back at the station!!! How long does it take to not load a train???
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Gotta ride 'em all!