A project involves completion of number of activities. The cost/duration of the project depends upon the activities, change in the duration and hence cost of an activity affects the project duration and the total cost of the project.

Time-cost Optimization determines duration and corresponding cost. It is also called as Time-cost trade-off.

The objective of time-cost optimization is to determine the normal duration of the project, the minimum possible duration of the project and the optimum duration of the project and the corresponding project costs. The technique used in time-cost optimization are-

• Compression
• Decompression

Compression of an activity refers to the reduction in the duration of an activity by increasing the resources allocated to it or by lowering the technical specification of the work. The process of shortening a project is called crashing and is usually achieved by adding extra resources to an activity.