One of the practices used in TameFlow Kanban is that of identifying the constraint in the work process, by looking for the work state that takes the largest average flow time. In the Kanban Method bottlenecks are typically identified by looking for queues and/or starvation. The work state in front of one that is being starved, could be a bottleneck. A work state where there are queues could also be a bottleneck. Naturally, when work state WIP limits are employed, queues are more difficult to see; but starvation is always evident.
This is a companion discussion topic for the original entry at https://chronologist.com/blog/2014-04-15/bottleneck-in-the-work-flow-vs-constraint-in-the-work-process/