The following article by David Webb and David Tuma is from a few years back
Disciplined engineering is an important factor. It’s a necessary but insufficient condition.
The unique features of personal TSP earned value tracking include
- engineers are trained to better make fine grained estimates
- personal schedules include personal effort available and individual workloads
- the resulting task schedules are tracked
- workload is rebalanced when task variance brings individual schedules out of alignment.
The last point, workload rebalance is the final critical piece. Rebalancing, shifting work from one individual to another, keeps the team working at near full effort. In the absence of continuous rebalance, workers are idle while waiting for the next assignment.
Variance happens. Components are bigger or smaller than estimated. Some may be more complex or simpler. Individuals may have pop up tasks that reduce project effort (or may achieve more project time than planned).
Rebalance is not unique to TSP. There are other agile approaches such as reallocating in daily stand ups or picking tasks off the bulletin board. What makes TSP unique is the fine grained information available. Specifically TSP records
- individual work package size (e.g. LOC or pages)
- individual work package task (or direct) hours
- indivual task completion dates
Unlike so-called velocity, the nearest TSP equivalent, Cost Performance Index (CPI) distinguishes schedule performance slips as a result of overall estimation bias, indivual estimation variance, rate bias, work in progress or effort availability. As the team tactically rebalances the work plan, they can discuss the root cause of the change and take appropriate actions. Those actions might include re-estimating, replanning, or asking for management for help.