Critical Path

The critical path is the longest chain of dependent activities in a project schedule that determines the overall project duration. Tasks on the critical path have zero float (slack), meaning any delay to a critical path task directly delays the project completion date.

Critical Path Method (CPM) process:

• List all activities: Identify every task needed to complete the project
• Determine dependencies: Identify which tasks depend on other tasks completing first
• Estimate durations: Assign time estimates to each task
• Build the network diagram: Map out the task dependencies visually
• Calculate the critical path: Find the longest path through the network
• Identify float: Determine how much flexibility non-critical tasks have

Key CPM concepts:

• Early start (ES): Earliest a task can begin
• Early finish (EF): Earliest a task can finish
• Late start (LS): Latest a task can start without delaying the project
• Late finish (LF): Latest a task can finish without delaying the project
• Float/Slack: The amount of time a task can be delayed without affecting the project end date
• Near-critical path: Tasks with very little float that could become critical

Managing the critical path:

• Focus management attention on critical path tasks
• Assign the best resources to critical path activities
• Monitor critical path progress closely
• Have contingency plans for critical path delays
• Consider crashing (adding resources) or fast-tracking (parallelising) to shorten the path
• Re-evaluate the critical path when scope changes occur

Limitations of CPM:

• Assumes task durations are deterministic (PERT addresses this with probabilistic estimates)
• Does not account for resource constraints (Critical Chain Method adds this)
• Network can change as the project progresses
• Complex projects may have multiple near-critical paths