Creating a realistic project schedule is one of the biggest challenges a project manager faces. There are some common problems with project scheduling that can be anticipated and prevented, giving everyone involved with the project more confidence in the schedule.
The most basic and common problem with project scheduling is estimating the duration of each project task. Most people underestimate how long something will take them to do, resulting in a schedule that reflects only a best-case scenario. To prevent this, you can add time to each task if you can guesstimate how much your team member has underestimated. (Many people underestimate consistently by a certain percentage.) Or you can add contingency time as a separate item in your schedule. While this is sometimes frowned on as “padding” your schedule, it is actually a realistic way to make your plan more accurate.
Be sure not to miss any necessary project tasks. It’s easy to overlook those done by groups outside your project team or those that the subject matter expert doing the estimating thinks are so obvious that she doesn’t need to mention them.
Most project schedules are based on the assumption that the right resource person will be available exactly when needed. But unless your organization has a good method for assigning people to projects, that may not happen. Your schedule also needs to realistically account for how much time each team member can spend on your project, considering other projects, operational support or administrative tasks they must do.
In many cases, management or some outside factor has set the project implementation date before you develop a schedule. You may be asked to reduce the time planned for some tasks to meet the needed end date. You should proactively communicate to the project sponsor any risks involved in making these changes.
Unknown events, such as changes in the business environment or problems with a new technology, may result in project tasks taking longer than scheduled. By identifying possible risks at the beginning of the project you’ll be able to better manage any that occur and thereby reduce their impact to your schedule.
Changes to the scope of the project, requirements to be accomplished or technology being used may disrupt your project schedule. These kinds of changes should go through a formal project change management process so the project sponsor and customers can agree to any schedule changes rather than being unpleasantly surprised by them.
A large project has more interdependencies between tasks and between work groups or individuals. This level of complexity makes it harder to predict the schedule, which will need to include time for such coordination.