Firstly, a confession...

I like McDonalds. No, I love McDonalds. I hate much of the side effects of this huge corporation, and I know the 'food' sold is junk. No nutritional value, high salt, saturated fats etc. However, it's tasty, convenient and somehow satisfies in ways other fast food can't. However, today, I really noticed Theory of Constraints in action - or not.

As any McDonalds drive through customer knows, service is normally fairly fast and efficient. However, on occasion, your food order takes longer than average to prepare. Maybe they have just put a batch of fries on, or have just prepared a tray of patties ready to cook. So what do they do?

They advise the driver to park in a bay and wait for their food whilst they continue receiving, processing and delivering other orders. This sometimes make sense - why force other customers to wait whilst' they complete the previous customers order.  And in many cases of occasional spikes in demand, this strategy works. The only people slightly inconvenienced are the hungry customers parked in the bay. Still, they'll be ok in 3 minutes, when they get their Big Macs or Fillet o'Fish (yeah right...)

However, what happens when sustained increase in demand occurs, rather than a short spike. I experienced this today and noted several observations...

The Situation

Cheryl and I were about sixth inline at the drive through at Tamworth McDonalds and I was HUNGRY. We noticed that several cars in front ordered quickly, and progressed past the food delivery window way to fast for this to be normal service. Instead, each car either parked in a waiting bay, or in the main car park. Due to the speedy queue, we ordered quickly, and were advised to park in the car park, and wait for our food. We dutifully followed orders and waited. And waited. And waited. And waited. And most importunity for this blog post at least, observed as customers behind us in the queue joined in the melee.


  1. When we followed the cashiers advise to park in the main car park and await food, we quickly became aware that there were no spaces available. None at all. So we had to double park 3 other customers which was luckily ok, as we were still in our car and so could move if they needed to leave. However, more and more customers were following our actions, and filling up the car park. This meant that would-be customers wishing to sit in couldn't due to the full car park! At least this would have the side effect of reducing demand on the true bottleneck - the kitchens.
  2. Bystanders, or possibly management might not have been aware of the problems as observing drive through throughput would appear high - people were ordering, and driving past the delivery window quickly, and the queue was rapidly declining. There was little immediate, direct visibility of system performance issues. In fact, the main warning was the busy car park! That was probably attributed to high demand for sit-in customers - WRONG!
  3. Kitchen or serving staff were wasting significant effort in carrying food across the car parks to identify and serve food the customers. This was putting even more stress on staff that could have been more usefully deployed to the kitchen bottleneck.
  4. Luckily, our food was still hot when served, but the large batches of customer orders must have been siting in preparation in the kitchen before being delivered by the high mileage staff, thus cooling, and degrading (slightly) in quality.
  5. Customers had little visibility of progress as they were sitting in the car park, and food was being severed in order of completion, rather than in the order of the drive through queue - slightly frustrating.


This 25minute or so episode could be put down to an infrequent spike in demand, but was fairly lengthly. Lunchtime demand at McDonalds could have continued for another hour or more, and this unmaintainable situation could have escalated. Money would have been lost with sit in customers failing to find a car parking space, and thus turning away. Further, drive through customers frustrated by both a long wait and seemingly incompetent staff would by less likely to consider McDonalds for Saturday lunches in the future.

Following Theory of Constraints advise, optimisation should be applied at the bottleneck (kitchens) rather than at non-bottleneck processes. Therefore, staff being deployed to deliver food to cars in the car park could be deployed to aid in the kitchen bottleneck. Even if this could not be enabled (due to training, kitchen capacity etc), then at least serialising processing of customers through the queue would clearly identify the kitchens as the bottlenecks, and thus advocate investment / future optimisation in this department. It would also prevent any mis-indications that the car park was too small for the restaurant - it was only full due to serving as a car park, and buffer for drive through customers.

Anyhow, after a longer than convenient wait, we enjoyed our lunch. And it provided an great opportunity for me to observe Theory of Constraints in action.

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