Leads and Lags are two important concepts in the Schedule Management knowledge area and deserve a separate article. So here’s the separate article on leads and lags.
In an ideal World, all the project activities are sequentially lined one after the other. As a Project Manager, you ensure all the activities are completed on time. But to think of it, is that really an effective way to manage project? If you run two activities in parallel, wouldn’t that save time?
While running activities in parallel sounds great, in the real World project management situations, you may end up intentionally waiting between two activities as well. Now what kind of Project Manager in her right senses intentionally add a delay between two project activities? Someone who knows the concepts of leads and lags!
In theory, the waiting time between two activities is known as Lag. Please note that Lag is not about missing deadlines, it is purposeful.
Lead on the other hand is letting an activity begin (and be conducted in parallel) with its predecessor. Note that the predecessor activity hasn’t finished yet. Obviously there is a significant risk of rework involved with lead
Examples of Lead
- You can start the project design while still working on collecting requirements. All you need is the portion of requirements that is frozen
- Setting the microwave oven on preheating while working on the mixture
- If the photo shoot is going to take 3 days and editing another 3 days, you can begin editing after the first day of the shoot
Examples of Lag
- After plastering the wall is complete, you need to wait for the cement to set before paint can be applied
- Once the goods are shipped to the customer, you need to wait before reaching out to the customer for delivery confirmation
- When the edited photos are sent to the customer for review, there is a week’s delay before the customer approval is obtained and photos can go for printing
Mathematical representation of Leads and Lags
Lag describes delay. It means addition of time so it is denoted by “+” sign in the network diagram. Lead always describes advancement. This means reduction in time taken so it is denoted by “-” sign in the network diagram.
In conclusion, do note that leads and lags are both used in the development of the project schedule.