Critical Chain Project Management BA 341 Lean Operations Dr Bogdan Bichescu 1 Some Project Success Statistics According to a 2015 Standish study 53 00 29 00 18 00 2 Theory of Constraints to the Rescue Critical Chain Introduced by Eli Goldratt in The Critical Chain 1997 Challenges conventional project management approaches Relies on TOC principles to answer What to change What to change to How to cause the change 3 What to Change Deeply rooted behavior associated with traditional project management practices Parkinson s Law Work expands to fill and often exceed the time allowed Sandbagging Early task completion does not get reported Student Syndrome Always wait to the last minute to start a task 4 What to Change Is Multitasking Beneficial Multitasking implies starting work on a new task project before finishing the current one Assume the example of 3 tasks that have to be executed by the same resource A 10 B 8 C 6 When can task A be finished A 5 B 4 C 3 A 5 B 4 C 3 How about now 5 What to Change to Use Aggressive but Possible Times ABPT Cut task durations in half Use Aggressive but Possible Times ABPT Regular safe duration estimate 6 What to Change to Identify the Critical Chain The longest sequence of dependent events that prevents the project from completing sooner based on ABPT durations The correspondent of the constraint in a project environment Task and resource dependencies are key in identifying the critical chain 7 What to Change to Use Buffer Management in the form of Project Buffer Added at the end of the project Protects final project completion date from variations in the duration of critical chain activities The size of the buffer should equal about half of the safety removed from the tasks that make the critical chain that is half the length of the critical chain Cr Activity 1 Cr Activity 2 Cr Activity 3 Project Buffer 8 What to Change to Use Buffer Management in the form of Feeding Buffers Placed at the merging points between a non critical chain and the critical chain Protects the critical chain from variations in the duration of non critical activities The size of the buffer should equal about half of the safety removed from the tasks that make that specific non critical chain Cr Activity 1 Cr Activity 2 Cr Activity 3 Non cr Activity Feeding Buffer Project Buffer 9 What to Change to Use buffer consumption to track project progress A function of the difference between the sum of actual completion times and sum of planned ABPT completion times Avoid displaying milestones ES EF LS LF Emphasize the Relay Runner work ethic Avoid using multitasking for capacityconstrained resources don t release projects as soon as soon as possible when there is a capacity constraint 10 Let s Consider an Example Assume the following project where the letters represent resources and numbers activities 1V 2W 3X 12 days 12 days 20 days Start 4Y 5X 16 days 20 days 6Z End 24 days Further assume that activity durations have been determined in the traditional way i e have been individually padded for safety 11 Let s Apply CCPM to our Example First determine ABPT 1V 6 days 2W 6 days 3X 10 days 6Z Start 12 days 4Y 5X 8 days 10 days End Second identify the critical chain not required on final 1V 2W 3X 6 days 6 days 10 days 6Z Start 12 days 4Y 5X 8 days 10 days What is the expected project duration End 12 Let s Apply CCPM to our Example Third add the Project and Feeding Buffers 1V 2W 6 days FB 6 days 6 days 4Y 5X 3X 6Z 8 days 10 days 10 days 12 days Project Buffer 20 days Fourth use buffer management to monitor project progress Assume that project is now at end of day 15 but task Y has just been finished Has any buffer time been consumed 13 Let s Apply CCPM to our Example Using Buffer Management Percent buffer project consumption is 7 days 20 days 35 How do you feel about project progress to date Should we be alarmed 1 3 of Buffer 1 3 of Buffer 1 3 of Buffer Expected Variation Normal Variation Abnormal Variation Reflects inherent task uncertainty No intervention needed While still reflective of normal task uncertainty plans should be made to recover lost time if project delayed to red zone Reflective of abnormal special cause variation Corrective actions should be taken 14 Percent Buffer Consumed 0 100 Using a Fever Chart to Track Projects Identify and solve problems Monitor Carry on with the project 0 100 Percent Project Completed 15 Summary of the Critical Chain Approach 1 Use Aggressive but Possible Times ABPT for task durations 2 Identify the Critical Chain by taking into account resource dependencies 3 Use Buffer Management to track project progress 4 Avoid Multitasking when faced with a capacity constraint 16