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You have 14 minutes to leave
Even if that may sound as a threat coming from a cheap action movie lines, where the main actor is struggling to get out of a building on fire… it’s not. It’s actually the message i’ve been seeing for many years after paying for my time in different parking lots, that one day suddenly changed.
The level of attention i gave to this in the past to that message, was just in the line of:
- Why 14 minutes? Why not 15 or 10?
- Where does that number come from? Some sort of mean + margin based on the exit time of the parking?
- Why mostly all the parking machines i used have the same number configured?
That questioning never elapsed longer that the journey from the payment machine to my car, but one day something different happened:
While paying the parking at the office, I had trouble with one my credit cards, mainly because two reasons:
- Some incident not worth mentioning that disabled two of the three cards i had in my wallet.
- The lousy experience of changing user interface between the main parking payment screen and the separate credit card module, that didn’t say a word about a problem with the credit card.
And there i was, retrying cards with no success, until i realized that the problem were my two main cards. I picked the third one that i barely use, it worked flawlessly, I returned to the main screen, picked up my validated ticket, and when i was about to leave, i looked at the screen, and i saw these:
You have 11 minutes to leave
11 minutes. 11. Eleven. WHY.
The obvious answer thay you may have tought is that the time i spent playing card games with the paying machine was substracted from the original 14 minutes, that’s what i thought also, and probably it is, and there is were my head exploded, dissecting how that was probably implemented and questioning why it was done that way:
I assume that the time that is shown in the screen is used to forbid the exit to the car associated with a certain ticket, if it takes more that the infamous 14 minutes to exit. I didn’t field-test it (yet). So i guess it’s not just a info message on the screen, it’s stored somewhere in the logic of the system.
I also assume that, as i said previously, if I got 11 minutes it’s because the system substracted the time i spent in the operation. Thinking in the implementation, either a countdown timer was started when the operation started, or a timestamp was registered. In the first case, the time shown would be the remaining countdown, and in the timestamp one, the difference with the current time. Without knowing anything of the hardware neither software on this machines i would say the timestamp, because is how i would do it.
This led me to an answer: the 14 minutes were not 14 minutes, they were 15 minutes that started at some point in the operation, and somehow my mean time paying a parking ticket is less that one minute, reason why I always see 14 minutes in the screen. But with that answer, it came another question:
Why setting that time reference at the beggining of the operation? I don’t care what the 15 minutes number comes from, but if somehow it’s a realistic number regarding mean exit time of a parking, doesn’t it make more sense to start counting once the operation is done, and give you a straigh 15 minutes, that you don’t even need to calculate.
This is one example of something that happens to me more or less regulary, i cannot avoid thinking about how things are done, not only software, almost anything is put in front of me. Sometimes is a pleasant experience, because it makes you learn new things, sometimes it leaves unanswered stuff on my head. Does it happen the same to you?
If you happen to be an engineer working on parking paying machines, please save me some brain processing cycles and show me the truth!
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