Which Queue?

If you are to line-up at a fast food counter, which line would you prefer? The normal or natural choice is the shortest one. But that is not necessarily the fastest. It depends also on who is in front of you, and who is serving the counter.
If you have a group of teenagers in front, not too bad. They may have made up their minds based on previous orders, or based on the depth of the purse which depends on what part of the month it is. A family with several kids can take quite a while to constitute the order, or to get the approval of the sponsor. Pensioners? seldom that this breed of people seen lining up there. At the most they sit it out at a table somewhere while a proxy is in the queue.
Too bad if you have a family with several kids served by a trainee cashier. The delay will be multiplied, and your patience gets shorter. Supermarkets sometimes like to put trainee cashier at the express counter, thinking that it is easier than dealing with bulk buyers. But the very spirit of expediting the transaction more often than not are compromised. The advantage of the express counter, to the customer, is nullified or reduced, which can sometimes be frustrating as gap between expectation of speed and reality begins to develop in the mind of customers and widens as the moment ticks by.