More grocery stores should move to a non-gameable queuing system. It seems that there is no agreement on the best setup as the stores I see in New York have wildly different systems. E.g.:

• My neighborhood supermarket has 8 registers with their own lines, 1 of them is express
• Wholefoods on 25th and 7th has 4 lines for 10 active registers, and 1 line for 4 express registers
• Trader Joe's on 21st and 6th has 2 lines for 10 active registers, and no express lines

For the shopper, the best grocery-shopping experience is focusing on picking out food and then getting out as quickly as possible. I don't want to think about which lane is best and I don't want to feel stupid/unlucky for choosing the wrong lane. Also, extremely long lines can be annoying as constantly moving a few steps at a time is quite frustrating.

The store wants to use their checkout-clerks and cash-registers most efficiently in both high-traffic and low-traffic situations, keep the check-out line out of the way of shoppers, and ideally generate incremental sales from people in the checkout line. Some stores do this with gum and magazines near cash registers, others wind the lines through snack-food aisles - generally it's a focus on high-margin, non-staple items. Given the overall low-margin/high-volume business, the store's top priority is probably optimizing the customer's experience. Customers are unlikely to abandon their full grocery carts when they see long or slow lines, but they may choose to shop somewhere else in the future.

A good solution is one where the customer doesn't need to think about where to go, spends a 'reasonable' amount of time waiting for checkout, and stands next to high-margin items while they wait. I think that Trader Joe's is closest to nailing it down. When the lines are long, they wind shoppers all through the store including standing right in front of the free sample table. In addition they have an employee at the front of the line ensuring that no one misses a cash-register and an employee at the back of the line telling shoppers which line to choose.

The Wholefoods line system is great for customers when the store is crowded - you don't have to slowly traverse the whole length of the store (like the long Trader Joe's line) and they have minimized wait times and maximized checkout utilization. However, the downsides are: from the store's perspective, people are exposed to less product during their waits and for the customers there is still some gaming in terms of which line to choose (though this is mitigated because each line leads to the same bank of registers, so a single slow transaction doesn't affect one line more than any other). However, when lines are empty or almost empty, poor line-choice can result in a huge increase in the expected waiting time.

Express lines can be a good idea, but only if all of the registers are constantly in-use or the express registers can become non-express seamlessly. Unless customers really want an express line, it's unlikely that the extra space and organizational overhead make Express Lines worthwhile. Similarly, Cash-only lanes probably aren't worth the overhead.