---
title: "Critical path, characteristics and importance"
subject: "Project Engineering"
chapter: 3
key: "semester_7/project_engineering:critical-path-define-characteristics"
source: https://www.bctengineer.com/q/semester_7/project_engineering/critical-path-define-characteristics
site: BCT Engineering
---

# Critical path, characteristics and importance

Project Engineering · Chapter 3: Project Planning and Scheduling

- Asked in: 2081 Bhadra, 1+3 marks
- Video: [What is Critical Path in Project Management?](https://www.youtube.com/watch?v=vV3YUaUg5i8) — Wrike
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_7/project_engineering/critical-path-define-characteristics
- Whole chapter: https://www.bctengineer.com/md/semester_7/project_engineering/chapter-3

## Question

Define critical path. Write down its characteristics in the network diagram of project activities and mention its importance.

## Short answer

The critical path is the longest path from start to end event with zero total float. Its activities have EST=LST and EFT=LFT, its events have zero slack, a delay in any critical activity delays the whole project, and more than one critical path can exist. It gives the minimum completion time and directs management attention and crashing.

## Answer

#### Definition

The **critical path** is the longest path (sequence of connected activities) from the start event to the end event of the network. Its length is the project duration, and it is the path with zero total float.

#### Characteristics
1. It is the longest path in the network; no other path takes more time.
2. All activities on it are critical: TF = 0, so EST = LST and EFT = LFT.
3. Events on it have zero slack: TE = TL.
4. It runs continuously from the start to the end event.
5. A network may have more than one critical path.
6. A delay in any critical activity delays the whole project by the same time.
7. It can change when activity durations change (a non-critical path may become critical when its float is used).

#### Importance
- Gives the minimum project completion time.
- Shows where management attention and best resources should go.
- Only critical activities need to be shortened for crashing the project.
- Float on other activities allows shifting and resource levelling.
- Base for monitoring, updating and claims for time extension.

## Check yourself

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

1. What is the total float of critical activities?
   A. Zero
   B. Equal to the activity duration
   C. Positive and equal to free float
   D. Negative
   Answer: A. On the critical path TF = 0, so EST = LST and EFT = LFT. (Key point: Float on critical path)

2. What is true of events on the critical path?
   A. TE is greater than TL
   B. TL is greater than TE
   C. Slack is zero, TE = TL
   D. Slack equals duration
   Answer: C. Critical events have no slack. (Key point: Event slack)

3. Can a network have more than one critical path?
   A. No, only one is possible
   B. Yes
   C. Only if there are no dummies
   D. Only in PERT
   Answer: B. Several paths can have the same longest length. (Key point: Multiple paths)

4. Can the critical path change during the project?
   A. No, it is fixed from the start
   B. Only when the project ends
   C. Only when dummies are removed
   D. Yes, a non-critical path can become critical when its float is used up
   Answer: D. Changes in durations alter which path is longest. (Key point: Change)

## Related in Project Engineering

- [Critical path and dummy activity significance](https://www.bctengineer.com/question.md?key=semester_7%2Fproject_engineering%3Acritical-path-dummy-significance) — Project Engineering, chapter 3
- [CPM network, 12 activities (A=1 to L=4)](https://www.bctengineer.com/question.md?key=semester_7%2Fproject_engineering%3Acpm-network-twelve-act-k81) — Project Engineering, chapter 3, asked 2×
- [CPM precedence diagram, 9 activities](https://www.bctengineer.com/question.md?key=semester_7%2Fproject_engineering%3Acpm-network-precedence-k72) — Project Engineering, chapter 3
- [Dummy activity; use of critical path in CPM](https://www.bctengineer.com/question.md?key=semester_7%2Fproject_engineering%3Adummy-critical-path-use) — Project Engineering, chapter 3
- [CPM network, 10 activities (A=4 to J=9)](https://www.bctengineer.com/question.md?key=semester_7%2Fproject_engineering%3Acpm-network-ten-act-as70) — Project Engineering, chapter 3
- [CPM network, hydropower project (months)](https://www.bctengineer.com/question.md?key=semester_7%2Fproject_engineering%3Acpm-network-hydropower-k80) — Project Engineering, chapter 3

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