Microsoft Office Tutorials and References
In Depth Information
Allowing for Murphy’s Law:
Lag and lead time
Dependencies can get a little more complex than simply applying the four
types of dependency links I describe in the preceding section. You can use
lag time or lead time to fine-tune your timing relationships:
Lag time occurs when you add time to the start or finish of a
predecessor task; lag time causes a gap in timing.
Lead time is created when you subtract time from the start or finish of
the predecessor; lead time causes an overlap between two tasks.
Here are a couple of examples:
You want to launch a new toy product into the market and set up a
start-to-start dependency relationship between the Begin Print Media
Advertising predecessor task and the Begin TV and Radio Advertising
successor task in your project. In a simple start-to-start relationship,
both tasks start at the same time. If you want the TV and radio ads to
come out a week after the print ads begin, though, you build in a week
of lag time to the start-to-start relationship where Begin Print Media
Advertising is the predecessor and Begin TV and Radio Advertising is
the successor. TV and Radio ads will now start one week after print ads
begin to appear.
In a project to train a new set of volunteer docents to give tours of a
historic mansion, suppose that you create a finish-to-start relationship
between the two tasks Locate Recruits and Train Recruits. However, to
save time in your project, you decide to incorporate two days of lead
time — that is, allow the training of the earliest hires to start before all
the recruits are hired. In that case, you essentially deduct time from the
finish-to-start relationship that allows you to start training two days
before the finish of the Locate Recruits predecessor.
Making the Dependency Connection
Making dependency relationships is simple. You simply create a dependency,
make settings to select the dependency type, and build in any lag or lead
time. The tricky part comes in understanding how each type of dependency
affects your plan when your project goes live and you start to record actual
activity that resources perform on tasks.