In a process or system, a bottleneck refers to a congestion point that slows or limits output. To visualize a bottleneck, imagine a car accident that closes three lanes of a four-lane highway. The open lane will likely experience heavy traffic as drivers slow down and move into the open lane, creating a bottleneck.Bottlenecks can occur in almost any business process and can crop up due to inefficiencies that are either internal or external to the organization. For example, an internal bottleneck might occur if a stack of financial paperwork reduces the only hired accountant’s productivity. A global shipping route shutdown, on the other hand, may be external to affected manufacturers and retailers around the world, but those companies could still be affected.