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Dependencies and the Critical Path

Finding the path that determines your project's finish date.

Dependencies Create Sequence

Dependencies are logical links between tasks. The most common type is Finish-to-Start (FS): Task B cannot start until Task A finishes.

Dependencies create the network of your project. Some tasks can proceed in parallel; others must wait. This network of connections determines the minimum time needed to complete all work.

Float and Slack: Understanding Flexibility

Definition: Float (or Slack)

The amount of time a task can be delayed without delaying the project's finish date. Float = flexibility. A task with zero float has no wiggle room.

Example: A Simple Network

Imagine three paths to complete a project:

  • Path A: Task 1 (5d) → Task 2 (3d) → Finish = 8 days
  • Path B: Task 3 (10d) → Task 4 (2d) → Finish = 12 days
  • Path C: Task 5 (4d) → Task 6 (4d) → Finish = 8 days

The project takes 12 days (the longest path). Path A and Path C have 4 days of float — those tasks could each be delayed up to 4 days without affecting the project end date.

Float is valuable. It tells you where you have scheduling flexibility, where you can reassign resources, and which delays are acceptable.

The Critical Path

Definition: Critical Path

The longest sequence of dependent tasks in your project. It determines the minimum project duration. Any delay on the critical path delays the entire project.

Tasks on the critical path have zero float. There's no slack — they must complete on time or the project slips.

In the example above, Path B (Task 3 → Task 4) is the critical path. If Task 3 takes 11 days instead of 10, the project becomes 13 days. But if Task 1 takes 6 days instead of 5, the project still finishes in 12 days — because Path A still has 3 days of float remaining.

Functional Perspective: Keeping Your Project on Schedule

The critical path is your primary tool for schedule management. Here's how to use it in practice:

1. Know Your Critical Path

At any moment, you should be able to answer: "Which tasks, if delayed, will delay the project?" These are your critical path tasks. In Consequent, these are highlighted and can be filtered.

2. Focus Management Attention

Give critical path tasks priority for resources, attention, and problem-solving. A 2-day delay on a non-critical task might be acceptable; a 2-day delay on a critical task is a project-level problem.

3. Watch for Critical Path Changes

The critical path can shift. If a non-critical task gets delayed enough, it may become critical. If you accelerate a critical task, another path might become critical instead. Re-evaluate regularly.

4. Track Predecessors of Critical Tasks

A critical task's predecessors are equally important. Document all predecessors carefully — if any slip, the critical task (and the project) slips too.

Weekly Critical Path Review Checklist

  • Identify current critical path tasks — which activities have zero float?
  • Review progress on critical tasks — are they on track? Any blockers?
  • Check predecessors of upcoming critical tasks — is anything at risk of delaying them?
  • Look for near-critical paths — tasks with very little float that could become critical
  • Update the schedule — reflect actual progress and let the critical path recalculate

Why Critical Path Analysis Matters

Without critical path awareness, project managers often spend time on the wrong tasks. They chase small issues while major delays build up elsewhere. They optimize local performance while the overall schedule slips.

The critical path focuses your attention. It tells you, mathematically, which tasks matter most for meeting your deadline. Everything else is secondary.

Chapter Summary

  • Float (slack) is the time a task can slip without affecting the project end date.
  • • The critical path is the longest sequence of dependent tasks — it determines project duration.
  • • Tasks on the critical path have zero float — any delay on them delays the project.
  • • Focus management attention on critical path tasks and their predecessors.
  • • The critical path can shift — re-evaluate regularly.