Schedule Management

Lead and Lag

Lead

An acceleration of the successor activity.

Example: Finish-to-Start with -2 days lead means the successor can start 2 days before the predecessor finishes.

Use case: Painting can start 2 days before all drywall is complete (start painting finished rooms while others are still being drywalled)

Lag

A directed delay between activities.

Example: Finish-to-Start with +3 days lag means the successor must wait 3 days after the predecessor finishes.

Use case: Concrete must cure for 3 days before construction can continue

Exam Tips

• Critical path = longest path = shortest project duration
• Crashing = add resources = increases cost
• Fast tracking = do things in parallel = increases risk
• Always crash/fast track critical path activities first
• Lead = negative lag (acceleration)
• Lag = positive delay (waiting period)
• Float = flexibility in scheduling