Project Management guide · Scheduling and time
Schedule Compression: Techniques, Examples and Trade-offs
Schedule compression means shortening a project's schedule without reducing its scope. The two main techniques are crashing, which adds resources to critical activities at extra cost, and fast tracking, which overlaps activities that would normally run in sequence at extra risk.
Key takeaways
- Schedule compression shortens the timeline without cutting scope.
- Crashing costs money; fast tracking adds risk.
- Compress critical activities only, cheapest first, one step at a time.
- Recheck the critical path after each step.
When you need it
- A fixed deadline such as a regulatory date, event or contract penalty.
- The schedule is behind and shows negative float.
- Finishing early has a clear financial benefit, such as earlier revenue.
- A key resource or window, such as a shutdown period, is only available on certain dates.
Techniques compared
| Technique | How it works | Main trade-off |
|---|---|---|
| Crashing | Add people, overtime or equipment to critical activities | Higher cost |
| Fast tracking | Overlap activities or run them in parallel | Higher risk of rework |
| Change logic | Remove or rethink discretionary dependencies | May need new methods |
| Reduce scope | Deliver less, or deliver some items later | Less value now; needs approval |
| Improve productivity | Better tools, fewer interruptions, fewer handoffs | Takes time to work |
See fast tracking vs crashing for a detailed comparison.
How to compress a schedule
- Confirm the target date and how many days must be saved.
- Identify the critical path and near-critical paths.
- List options for each critical activity: can it be overlapped, and can it be shortened by adding resources?
- For crashing, calculate the cost per day saved (crash cost slope) and pick the cheapest first.
- Shorten one day at a time and recheck the critical path, since another path may become critical.
- Stop when you reach the target, or when further compression costs more than the benefit.
- Update the risk register, budget and baseline through change control.
Worked example
Our 14-day network has critical path A-B-D-F. The sponsor wants 12 days.
| Option | Days saved | Extra cost or risk |
|---|---|---|
| Crash D (5 to 3 days at $1,500 a day) | 2 | $3,000 |
| Fast track D to start 2 days before B finishes (FS-2) | 2 | Installers may work around missing furniture |
| Crash B (4 to 3 days at $2,000 a day) | 1 | $2,000 |
Crashing D by 2 days gives 12 days for A-B-D-F, while A-C-E-F is still 10 days, so the target is met for $3,000. Fast tracking D would save the same time with no direct cost but more risk. The full crashing calculation is in fast tracking vs crashing.
Risks and tips
- Adding people to late work can slow it down at first because of onboarding and coordination.
- Overlapping activities increases rework if early outputs change.
- Compression often uses up float, creating more critical paths and less resilience.
- Overtime for long periods lowers quality and morale.
Free templates for this topic
Frequently asked questions
What is schedule compression?
Shortening the project schedule without reducing scope, mainly by crashing or fast tracking.
What are the two main schedule compression techniques?
Crashing (adding resources at extra cost) and fast tracking (overlapping activities at extra risk).
Which schedule compression technique is cheaper?
Fast tracking usually has little direct cost but increases risk. Crashing has a direct cost.
Can reducing scope be schedule compression?
Strictly, no, because compression keeps scope the same. Reducing scope is a separate option that needs approval.
What is crash cost slope in schedule compression?
(Crash cost - normal cost) / (normal duration - crash duration), the cost of each day saved.
Why should schedule compression only target critical activities?
Because only critical activities determine the project duration.
Does schedule compression increase risk?
Yes. Both techniques reduce float, and fast tracking increases the chance of rework.
What is resource levelling vs schedule compression?
Resource levelling usually lengthens the schedule to fix overloads; compression shortens it.
Can Agile teams compress a schedule?
Agile teams usually hold the date and adjust scope by prioritising the product backlog.
When should you stop compressing a schedule?
When you hit the target date, or when the cost or risk of the next day saved outweighs the benefit.