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Escalator Queue Reduction: What does it have in Common with Transformational Supply Chain Management?
Simon Eagle uses escalator queues to explain how the principles of successful queue management can be used to accelerate the supply chain’s throughput
No, this isn’t about those escalators that only start moving when you step on them, or the way the Underground operators change the mix from two going up and one going down and vice versa depending upon the weight and direction of traffic at rush hours – although both are indeed a form of demand-driven escalator management. This is about a subtle but ingenious way to accelerate people up the extremely long exit escalators at Holborn Underground Station in London, where there is a tendency for the crowds to be queuing down the platform at rush hour.
The English are fantastic at queuing, be it for buses, taxis or trains – usually very polite, few sharp elbows and, on escalators, very disciplined at standing on the right to let those in a hurry pass on the left. So what was done in Holborn in 2016 was quite a culture shock: standing on the right and left was obligatory.
The reason for the change was London Underground officials hypothesizing that, by encouraging people to enter the escalator in pairs, the effective capacity of the escalator would be increased and the platform queues cleared more quickly. What this would mean is that individuals in a hurry wouldn’t be able to get through on the affected escalators, but the average wait time for all those in the queue (or the average speed with which all people exit the platform) would be increased.
In effect, the underused capacity on the left-hand side of the escalator would no longer be sacrificed for the benefit of those in a hurry. Initial trials demonstrated the truth of the hypothesis: the queues cleared 30 per cent more quickly.
What has this to do with Transformational Supply Chain Management?
Well, what are static inventories in a supply chain if they aren’t queues of materials waiting to be moved: either bought by customers or processed by machines or people? And, just as the operators of Holborn Underground Station were able to reduce the queues (or inventories) by improving capacity utilization and throughput by fully filling the left-hand side of the escalator with passengers, instead of it being partially used by those in a hurry, so Supply Chain Managers can make far better use of their scarce supply capacity. They can do so by eliminating its use by expedited and 'hot list' items that disrupt otherwise efficient schedules and use up capacity through, for instance, unplanned machine change-overs.