As I entered the 30-minute "U.S. Citizens" queue for immigration back into the U.S. last week, the helpful "queue manager" handed me a brochure. This is a great place to hand me something to read, because I'm captive for the next 30 minutes as I await my turn with the immigration officer at the Passport Control desk. The brochure said "Roll through Customs faster."Ok. I'm listening.Inside the brochure, the first page lays out the main benefits:
Well, that's pretty cool. Especially as I'm standing only 5% deep in a queue with a couple hundred people in it. And look, there's a Global Entry kiosk right there with its own special queue, with nobody—nobody!—in it.If I had this Global Entry thing, I'd have a superpower that would enable me to zap past the couple hundred people in front of me, and get out of the Passport Control queue right now. Fantastic.So what does this thing cost? It's right there in the brochure:
So, all in all, it doesn't cost too much: a hundred bucks and probably a couple hours one day next month sometime.What's the benefit of the queue-bypassing superpower? Well, it's clearly going to knock a half-hour off my journey through Passport Control. I immigrate three or four times per year on average, and today's queue is one of the shorter ones I've seen, so that's at least a couple hours per year that I'd save... Wow, that would be spectacular: a couple more hours each year in my family's arms instead of waiting like a lamb at the abattoir to have my passport controlled.But getting me into my family's arms 30 minutes earlier is not really what happens. The problem is a kind of logic that people I meet get hung up in all the time. When you think about subsystem (or resource) optimization, it looks like your latency savings for the subsystem should go straight to your system's bottom line, but that's often not what happens. That's why I really don't care about subsystem optimization; I care about response time. I could say that a thousand times, but my statement is too abstract to really convey what I mean unless you already know what I mean.What really happens in the airport story is this: if I had used Global Entry on my recent arrival, it would have saved me only a minute or two. Not half an hour, not even close.It sounds crazy, doesn't it? How can a service that cuts half an hour off my Passport Control time not get me home at least a half hour earlier?You'll understand once I show you a sequence diagram of my arrival. Here it is (at right). You can click the image to embiggen it, if you need.To read this sequence diagram, start at the top. Time flows downward. This sequence diagram shows two competing scenarios. The multicolored bar on the left-hand side represents the timeline of my actual recent arrival at DFW Airport, without using the Global Entry service. The right-hand timeline is what my arrival would have looked like had I been endowed with the Global Entry superpower.You can see at the very bottom of the timeline on the right that the time I would have saved with Global Entry is minuscule: only a minute or two.The real problem is easy to see in the diagram: Queue for Baggage Claim is the great equalizer in this system. No matter whether I'm a Global Entrant or not, I'm going to get my baggage when the good people outside with the Day-Glo Orange vests send it up to me. My status in the Global Entry system has absolutely no influence over what time that will occur.Once I've gotten my baggage, the Global Entry superpower would have again swung into effect, allowing me to pass through the zero-length queue at the Global Entry kiosk instead of waiting behind two families at the Customs queue. And that's the only net benefit I would have received.Wait: there were only two families in the Customs queue? What about the hundreds of people I was standing behind in the Passport Control queue? Well, many of them were gone already (either they had hand-carry bags only, or their bags had come off earlier than mine). Many others were still awaiting their bags on the Baggage Claim carousel. Because bags trickle out of the baggage claim process, there isn't the huge all-at-once surge of demand at Customs that there is at Passport Control when a plane unloads. So the queues are shorter.At any rate, there were four queues at Customs, and none of them was longer than three or four families. So the benefit of Global Entry—in exchange for the $100 and the time spent doing the interview—for me, this day, would have been only the savings of a couple of minutes.Now, if—if, mind you—I had been able to travel with only carry-on luggage, then Global Entry would have provided me significantly more value. But when I'm returning to the U. S. from abroad, I'm almost never allowed to carry on any bag other than my briefcase. Furthermore, I don't remember ever clearing Passport Control to find my bag waiting for me at Baggage Claim. So the typical benefit to me of enrolling in Global Entry, unfortunately, appears to be only a fraction of the duration required to clear Customs, which in my case is almost always approximately zero.The problem causing the low value (to me) of the Global Entry program is that the Passport Control resource hides the latency of the Baggage Claim resource. No amount of tuning upon the Passport Control resource will affect the timing of the Baggage In Hand milestone; the time at which that milestone occurs is entirely independent of the Passport Control resource. And that milestone—as long as it occurs after I queue for Baggage Claim—is a direct determinant of when I can exit the airport. (Gantt or PERT chart optimizers would say that Queue for Baggage Claim is on the critical path.)How could a designer make the airport experience better for the customer? Here are a few ideas:
Latency hiding is a weak substitute for improving the speed of the baggage claim process. The killer app would certainly be to make Baggage Claim faster. Note, however, that just making Baggage Claim a little bit faster wouldn't make the Global Entry program any more valuable. To make Global Entry any more valuable, you'd have to make Baggage Claim fast enough that your bag would be waiting for anyone who cleared the full Passport Control queue.So, my message today: When you optimize, you must first know your goal. So many people optimize subsystems (resources) that they think are important, but optimizing subsystems is often not a path to optimizing what you really want. At the airport, I really don't give a rip about getting out of the Passport Control queue if it just means I'm going to be dumped earlier into a room where I'll have to wait until an affixed time for my baggage.Once you know what your real optimization goal is (that's Method R step 1), then the sequence diagram is often all you need to get your breakthrough insight that either helps you either (a) solve your problem or (b) understand when there's nothing further that you can really do about it.