The Pros

Limiting parallel work is a means to improve (among others) efficiency of work systems. In the Kanban context such limits are called WIP (Work in Progress or Work in Process) limits. In case of Team Kanban for instance they are set at the team level for workstations (workflow steps).

It is in Team Kanban that a special flavor of WIP limits has been in use: the personal WIP limits. As its name implies, it imposes a limit on the number of work items (tickets) a team member might work on at any given time.

Personal WIP limits appear to have advantages such as

1. Easy to implement for physical (haptic) boards. Simply restrict the number of buttons each team member has at his disposal to mark the tickets he currently works on.
2. Reduces the occurrence of individual overload situations and thus reduces personal stress.
3. If every team member plays by the personal WIP limit rule, team WIP limits should not get breached.

Even Kanban methods such as Personal Kanban and the Kanban Maturity Model (KMM) make use of personal WIP limits. So why not use them? For many reasons I would say.

The Cons

Principles

Kanban is all about system thinking. It teaches to not fall into the trap of sub optimization: „the whole is bigger than the sum of its parts.“ But when it comes to personal WIP limits, the opposite is advocated.

Psychology

Personal WIP limits change the way individuals work. Such a change of one’s personal work system can lead to resistance and can lower the overall acceptance of the Kanban system, especially when it has just been introduced. When trying to improve a team’s efficiency, having the first measure aim at individual performance might be perceived as sending the message: „You need to change for us to succeed!“ That’s definitely not what Kanban is all about.

Operational Experience

1. While personal WIP limits are easily implemented with physical boards that is not the case with digital boards. You can only reach a mutual agreement and end up counting tickets assigned to the same team member.
2. Team WIP limits are simply more effective. For instance, if you start with the „1.5 rule“, that is setting the WIP limit at 1.5 times the number of workers at the workstation in question, you allow for some workers pulling a second ticket but not for all team members. That’s gives some freedom without running the risk of overburdening the team. That’s hard to be reached with personal WIP limits.
3. Let the team members discover their own personal WIP limits. With team limits in place, there will be limit breaches and the team will have to come up with solutions. Some team members (maybe more readily than others) will opt to reduce their personal workload.

In the end as always, do what fits your team.