In Kanban the number of work items in progress is limited. So what should we do if tight WIP-Limits and blocked work items impede the flow of work? Here are two approaches suggested by David J. Anderson in his book about Kanban.
How to Handle Blocked Work Items
Kanban systems bring visibility to problems and their impact. Handling impediments can be done in different ways, depending on the maturity of the organisation or team.
Two approaches can be used:
- Larger Overall WIP-Limit
- Stop the Line
Larger Overall WIP-Limit
Recommended for immature organisations
- explicit buffering
- increased WIP-limit (people can work on something else in case an item is blocked)
- Disadvantages of increased WIP-limit:
- lead time will be longer
- quality might be lower
- less/no tension to provoke discussion and implementation of improvements, which means the catalytic effect of kanban is lost!
Stop the Line
Recommended for mature teams familiar with root cause analysis
- tight policies, WIP-limits and buffer sizes
- stop the work when things come blocked
- idle people due to blockages raises awareness
- swarming to remove the blockage
- creates a culture of focussed continuous improvement