POSTER 24
Extension · Schedule Management
Schedule & the Critical Path
The critical path is the longest path through the network — it sets the shortest possible duration, and its activities have zero float. Find it with a forward & backward pass; protect it; and if you must go faster, crash (spend) or fast-track (risk).
Visual Map — A Worked Network
Forward pass sets ES/EF left→right (take the later predecessor at a merge). Backward pass sets LS/LF right→left (take the earlier successor). Float = LS − ES; zero float = critical.
Passes & Float
Forward: EF = ES + Dur − 1
Backward: LS = LF − Dur + 1
Total Float = LS − ES = LF − EF
Free Float = ESₙₑₓₜ − EF − 1
Critical path = longest path = zero total float. (Drop −1/+1 if counting from day 0.)
Schedule Compression
- Crashing
- add resources to critical-path tasks → adds cost. Crash the cheapest $/day first; watch diminishing returns.
- Fast-tracking
- overlap normally-sequential activities → adds risk & rework, no extra cost.
Both target the critical path — compressing anything else won't shorten the project.
Dependencies & Logic
- FS finish-to-start (most common) · SS · FF · SF (rare).
- Type: mandatory (hard) · discretionary (soft) · external · internal.
- Lead = overlap (negative lag); lag = imposed delay.
Exam Concepts
- Critical path = longest duration / least (zero) float.
- Float = LS − ES.
- Crashing adds cost; fast-tracking adds risk.
- Resource levelling can change the critical path & extend duration.
- Near-critical / multiple paths raise schedule risk.
Executive View
- Focus & protect the critical path — that's where time is won or lost.
- Compression always costs money or risk — never free.
- Float is manoeuvre room; watch near-critical paths.
Relationships
- The schedule baseline feeds EVM's PV (Poster 14).
- Schedule reserve covers schedule risk (Poster 12).
- Critical Chain adds buffers — a tailoring choice (Poster 5).
Industry Example
Manufacturing
- Line install: the critical path runs through long-lead equipment + commissioning. Fast-track civil works alongside procurement; crash commissioning with extra techs to recover a slip.
Memory Hooks
- "Critical path = longest path = zero float."
- "Crash = cash; Fast-track = risk."
- Float = LS − ES; relationships F-S, S-S, F-F, S-F.
60-sec Review
Find the critical path in the network
Forward & backward pass
Float = LS − ES
Crash vs fast-track
Name the 4 dependencies
PMI Visual Wall · Poster 24 · Schedule & the Critical Path · original instructional design · A3 landscape