Bottleneck

What it means

A bottleneck is the step in a process with the lowest capacity, which therefore limits the output of the whole process. However fast the other parts work, the whole cannot move faster than its slowest link. Work piles up in front of the bottleneck while people behind it wait for inputs.

The concept comes from manufacturing, where a bottleneck may be a machine, a workstation or a shortage of material. But it exists in services and administration too: in accounting it may be invoice approval, clients delivering documents, or one person without whom the month cannot be closed.

The theory of constraints and the lean and kaizen methods are all built on finding and removing bottlenecks. The core idea is to improve the bottleneck first, because improvements elsewhere will not raise overall output.

How it works in practice

When optimising processes with clients we first draw a process map and measure where the longest waits are. In monthly bookkeeping the bottleneck is often the client delivering documents, not the posting itself.

Once the bottleneck is found, we look for the root cause and a solution: relieve it of work others can do, make sure it never waits for inputs, or increase its capacity. With people, cover and clear rules help; with systems, automation.

In capacity planning we track the bottleneck’s utilisation as the key indicator. If it is fully loaded and demand is growing, investing in its capacity has the greatest effect; investment elsewhere will not show.

What to watch out for

Removing one bottleneck reveals the next. That is natural and means the process has improved. Improvement is therefore a repeated cycle, not a one-off exercise.

Trying to keep every part of the process fully busy leads to unfinished work piling up in front of the bottleneck. It is more effective to pace the other steps to what the bottleneck can handle and focus on keeping it running smoothly.