---
title: "Critical chain technique"
subject: "ICT Project Management"
chapter: 8
key: "semester_7/ict_project_management:critical-chain-technique"
source: https://www.bctengineer.com/q/semester_7/ict_project_management/critical-chain-technique
site: BCT Engineering
---

# Critical chain technique

ICT Project Management · Chapter 8: Project Time Management

- Asked in: year not given
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/ict_project_management/critical-chain-technique
- Whole chapter: https://www.bctengineer.com/md/semester_7/ict_project_management/chapter-8

## Question

What do you mean by critical chain techniques?

## Short answer

Critical chain scheduling modifies the critical path by accounting for resource constraints and uses buffers to protect the project end date. It removes safety from individual tasks, pools it into project and feeding buffers, and manages by monitoring buffer consumption instead of task deadlines.

## Answer

**Critical chain scheduling (CCPM)** is a schedule network analysis technique, developed by Eliyahu Goldratt (Theory of Constraints), that modifies the project schedule to account for limited resources and uncertainty. It is applied to the critical path method but focuses on resource constraints and uses buffers to protect the end date.

#### Key ideas
- Traditional estimates include hidden safety (padding) in every task. People waste it through **Student syndrome** (starting late), **Parkinson's law** (work expands to fill time) and **multitasking**.
- CCPM removes safety from individual tasks (uses 50% probability estimates) and pools it at the end as a **buffer**.
- The **critical chain** is the longest chain of dependent tasks considering **both task dependencies and resource dependencies**.

#### Types of buffers
| Buffer | Placed | Protects |
|---|---|---|
| Project buffer | At the end of the critical chain | Project completion date |
| Feeding buffer | Where a non-critical chain joins the critical chain | Critical chain from delays in feeding paths |
| Resource buffer | Alert before the critical task | Resource availability |

```text
Critical chain:  [A]--[B]--[C]--[D]--(Project buffer)
Feeding chain:   [E]--[F]--(Feeding buffer)--^ joins at C
```

#### Steps
1. Build the network with dependencies.
2. Estimate task times with 50% chance duration (aggressive).
3. Resolve resource conflicts by levelling.
4. Identify the critical chain.
5. Add project and feeding buffers (typically 50% of the removed safety).
6. Track using **buffer consumption** (green, yellow, red zones).

#### Advantages
- Shorter and more reliable schedules.
- Reduces multitasking and waste of safety.
- Focuses management on the constraint.

#### Limitations
Needs cultural change; estimates are difficult; not suited to all projects.

| Critical path | Critical chain |
|---|---|
| Task dependencies only | Task and resource dependencies |
| Padding in tasks | Pooled buffers |
| Float management | Buffer management |

**Example:** A software release with a few shared testers uses a project buffer of 10 days instead of adding 2 days to each task.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. How does the critical chain differ from the critical path?
   A. It considers both task and resource dependencies
   B. It ignores resources
   C. It considers task dependencies only
   D. It uses float management
   Answer: A. The critical chain is the longest chain of tasks considering both task and resource dependencies. (Key point: Critical chain definition)

2. In CCPM, what happens to safety time in individual tasks?
   A. It is removed and pooled as buffers
   B. It is eliminated with no buffer at all
   C. It is doubled
   D. It is hidden in each task
   Answer: A. CCPM removes padding from tasks (using 50% estimates) and pools it as project and feeding buffers. (Key point: Buffer use)

3. Where is a feeding buffer placed?
   A. At the end of the critical chain
   B. Before every task
   C. At the start of the project
   D. Where a non-critical chain joins the critical chain
   Answer: D. Feeding buffers protect the critical chain from delays in feeding paths; project buffer is at the end. (Key point: Feeding buffer)

4. What is 'Student syndrome' in the context of padded estimates?
   A. Starting a task late because there appears to be time
   B. Finishing early and reporting early
   C. Doing many tasks at once
   D. Work expanding to fill the time
   Answer: A. Student syndrome is delaying the start; Parkinson's law is work expanding to fill the time. (Key point: Student syndrome)

## Related in ICT Project Management

- [Project verification and inspection](https://www.bctengineer.com/question.md?key=semester_7%2Fict_project_management%3Aproject-verification) — ICT Project Management, chapter 7

## Related in other subjects

- [Line coding in PCM and the right technique](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Aline-coding-pcm-solution) — Telecommunications, chapter 3
- [Indicator organism; membrane filter technique](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Aindicator-organisms-membrane-filter) — Water Supply Engineering, chapter 4, asked 2×
- [Multiplexing techniques; analog one explained](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Alist-mux-techniques) — Data Communication, chapter 6
- [Vibroflotation technique](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Avibroflotation) — Foundation Engineering, chapter 10