Quick and Easy: The Difference between Critical Chain And Critical Path

Critical chain

The critical chain is a resource-oriented method and represents the longest chain of tasks, taking into account limited resources and is used with the aim of achieving the minimum project duration. The critical chain planning is not only about determining what to do and when to do it, but who actually does it. The critical chain method brings these two new thoughts to project planning: 

1. No Multitasking is not allowed!
2. There are no individual buffers!

1. No multitasking allowed

It has been proven that multitasking is a productivity killer and therefore extremely inefficient. So when you are under pressure to complete a project as quickly as possible, avoid multitasking at all costs. Here's how you avoid multitasking with the Critical Chain method:

The number of projects is limited and only approved if the resource capacity allows it. Each resource always only works on one task at a time, preventing them from switching between several tasks and resulting in long processing times. Resources can be allocated more effectively and efficiently when there is a clear prioritization of the projects and tasks. Resources working on a critical project element receive the support they need from the team and the organization to get their tasks done as quickly as possible. This includes, for example, minimizing or postponing daily business tasks.

How are tasks handed over? What if the predecessor has been completed and the successor can't start yet because the assigned resource is still busy with another task? The rule is a "no multitasking" afterall: every resource must dedicate 100% of their capacity to complete one task. But if you wait for the resource to complete their current task, you will have idle time during which the project process is at a standstill.  In order to avoid such idle times and multitasking, the project staff must be disciplined and follow the project process closely and, just like in a relay race, be ready to receive the "baton" from the predecessor.

^{This chart helps you identify which projects to prioritize with the critical chain method.}

2. Better effort estimation and inclusion of buffers

Buffers an be helpful leeway for unforeseen events that provide flexibility. Buffers can help prevent a delay in an activity from delaying the entire project. But buffers also have their downsides. Under Parkinson's Law work expands to the extent that time is available for its completion. In short, when we have more time to complete a task, we postpone the task and complete it just before the end. So we tend to procrastinate rather than get the job done as quickly as possible. So ultimately there is no buffer left and only delays in the project are passed on, but not in cases of early completion.

That's why the critical chain method doesn't have individual buffers. Instead, the procedure is as follows:

Project team members estimate the duration and 50% of this duration is used by the critical chain method as optimistic or minimum duration in the planning. The difference between these two durations is added as a time buffer across all activities and inserted at the end of the project.

Advantage of the critical chain method

The great advantage of this method is that you can shorten the project time significantly. The project duration can be shortened by about 25% and the adherence to the schedule can be increased to almost 100%. A further side effect is the quality improvement of the project result - as employees always concentrate on only one task at a time, so oversights and mistakes, which are often made when multitasking, can be avoided.

The critical path

The critical path represents the longest chain of activities and milestones for which there is no time buffer. This means that activities that are on the critical path must not be delayed, otherwise the total project duration is delayed by the same amount. On the other hand, if you finish activities that are on the critical path ahead of schedule, you can complete the project earlier as well. The method is used to identify bottlenecks in the project. It shows project managers activities where delays are risky, so you can take countermeasures from the start.

Avoid delays

To avoid delays in activities on the critical path, you can allocate additional resources to these activities. You should also try and work on critical tasks simultaneously if possible.

Advantage

The big advantage of the critical path is that you can quickly identify bottlenecks in the project and - in the best case - prevent risks in order to avoid delays.

Summary: Critical Chain versus Critical Path

^{Source: HS Augsburg Glossary}

Just as there is no clear answer in the discussion Agile versus waterfall planning, there is also no winner when it comes to Critical Path versus Critical Chain. It depends on the project and above all on the project team and the company culture. Although the critical chain method can shorten the project duration, a resource cannot always devote 100% to a task, for example.

Read more from the Quick and Easy series:

• The Difference between Effort and Duration