When a schedule is too long, the PMP exam gives you two ways to shorten it: crashing and fast tracking. Both work. The exam almost always hides one detail in the question that tells you which one is right.
The two techniques
| Crashing | Fast tracking | |
|---|---|---|
| What you do | Add resources to critical path activities | Run activities in parallel that were planned in sequence |
| Example | Add a second developer | Start testing before the build is finished |
| Main downside | Cost goes up | Risk of rework goes up |
| Changes the logic? | No | Yes, overlaps dependencies |
How to choose
- Budget is fixed, some risk is acceptable → fast track.
- Money is available, little tolerance for risk → crash.
- Only compress critical path activities. Shortening an activity with float doesn't shorten the project.
- When crashing, start with the cheapest cost per day saved on the critical path.
Worked example: which activity to crash?
You need to save two days. Activity B can be crashed for $800 a day, but B is not on the critical path. Activity C costs $1,500 a day, and E costs $4,000 a day. Both are critical.
- B is cheapest, but crashing it changes nothing, because it isn't critical.
- The cheapest critical activity is C: 2 days × $1,500 = $3,000.
A real-world example
A schedule had to shrink by two weeks. The team had budget, but the client had said: no extra technical risk before their compliance audit. Fast tracking adds risk, so it was out. The project manager crashed the critical path by adding a second developer. It cost more, but it respected the constraint that mattered.
Traps to avoid
- Crashing an activity that isn't on the critical path.
- Fast tracking when the question says risk must not increase.
- Crashing when the budget is fixed.
- Moving the schedule baseline without change control.
See it animated
The free chapter Plan and Manage Schedule includes a video with the critical path, forward and backward pass, and crashing vs fast tracking side by side. For the critical path calculation itself, read critical path and float for the PMP.