Everyday Parallelization

I just got back from some last minute purchases at our local Coles metro and it struck me how much I enjoy the checkout procedure.

After you have loaded all the goods out of your basket onto the bench, there is always a few moments while the cashier scans the remaining items. With the Coles system, I can swipe my frequent-shopper card, then my credit card and finally select the desired account.

It's a classically paralellizable situation . Two inter-dependant resources with multiple duties, some distinct some shared. One resource (the cashier) almost always takes longer and so it makes sense to allow the other resource (the shopper) to complete as many tasks as possible while it (you) would otherwise be in a blocked state.

It reminds me of discussions I used to have with my friend Matt about the implicit least-cost decisions involved in every day situations, such as picking pedestrian routes.

Does anyone else have examples of well designed human processes that exhibit good parallelization? Or the opposite?

PS: apologies for gratuitously making up words from the parallel stem!