Best practice vs Best workarounds

Best practice vs Best workarounds

Many planners mix up ‘Best scheduling practice’ with ‘best workarounds’ in a particular scheduling tool.

When they heavily apply one of scheduling tool, they start to believe that the workarounds are the best practice, refuse to learning alternatives and even debate that other tools must support such workarounds even if they are not required. The same applied to project risk managers.

How to avoid the ‘Overconfidence Bias’ trap?

  • Learn theories behind planning and risk management.
  • Always be curious about what a tool can’t do, whether workarounds are possible, and if they are, think about the downsides.
  • Look for chances to learn about other tools.

Remember, a not-so-great specialist just knows what a tool can do. A good one understands the problems and workarounds. An excellent specialist also knows the bad side of workarounds and can suggest other tools when needed.

Alex Lyaschenko

PMO | Portfolio Planning & Delivery | PMP | P3O Practitioner | AgilePM Practitioner | Six Sigma

Original Critical Path Method and beyond

Original Critical Path Method and beyond

Recently I have organised a Linked Poll on the origin of the Critical Path Method:

Originally in the Critical Path Method, project activities had to be estimated as:

• Single estimation
• Range
• 3-point estimation
• Don’t have duration

The accurate response, which was supported by a credible paper, was promptly shared in the comments, but it had little influence on the result. Nearly all participants stated that it relied on either a “single estimation” (48%) or a “3-point estimation” (41%). Merely 11% (!) provided the correct answer, which is that the critical path method originally requires estimation of each activity with time and cost ranges. These ranges extended from Optimistic to Normal estimates, as opposed to extending from optimistic to pessimistic estimates, as some respondents may have believed.

Let’s review how the Critical Path Method evolved over the time and what we can learn from the origin.

Two-phased method

The Critical Path Method (CPM) initially had two main phases. The first phase was known as the “time analysis phase,” while the second was the more complex “time-cost trade-off phase.” This is why CPM emerged in the late 1950s, as computers became accessible for analysis. The first phase, involving schedule time analysis, was quicker perform manually. However, the second phase, which required a heuristic solution, could not be carried out effectively without the aid of a computer.

The main goal of the Critical Path Method was to apply Heuristic Solutions to optimise project delivery plan, not to find critical activities based on expected durations.

Over the time the critical path method was split into two separate methods. The first phase of the original technique evolved into today’s CPM method, while the second phase became what we now know as the ‘CPM Least Cost Scheduling Technique’. Now most project delivery tools are only capable of supporting the first phase and do not include time-cost optimization analysis. These tools can calculate just two basic CPM metrics: Total Float and Free Float. They lack support for schedule optimization methods and metrics like Critical Path Activity Drag, Drag Cost, FLEX, Super Float. etc. 

Normal and Crashed durations

The fundamental assumption of the CPM model is that it is possible to assign a time range for each activity, indicating the time frame within which the activity is expected to be completed.

The duration of most tasks can fluctuate based on factors like the number of work crews, the efficiency of the machinery used, and the length of the workday, material supply. Typically, planners develop plan assuming a standard crew size, regular workdays, and the use of “owned” equipment when estimating the activity duration. These estimated activity durations under these conditions are referred to as Normal durations. When time is not a critical factor, management often allocates resources at the normal level.

In the CPM cost model, there’s another method for estimating time. In this approach, management considers the quickest possible time to complete activities. When there’s a strong deadline, management may allocate the best available resources and work around the clock to meet it. The fastest possible time required to complete an activity is termed the Crash Duration. In the CPM cost model, it is assumed that no activity can be completed faster than its crash duration. When management optimizes its resources to achieve each task at its crash duration, this scheduling approach results in a shorter overall project duration.

Changing the activity durations will affect the project duration and the project cost. From the project’s point of view, we can distinguish between two types of cost.

Direct and Indirect cost

The first type of costs is called the direct cost, and indicates the cost that is directly attributable to a task. The sum of the direct costs of a project’s activities is called the Project Direct Cost.

The other type of costs is called the Indirect or overhead Cost, also known as fixed cost. This type includes the cost factors that are not easily attributable to activities, but rather belong to the whole project. The elements of indirect cost are, for example, the amounts of rent of social facilities, management salaries, interest charges, etc. These costs are usually linear. One day saved on a project saves one day’s fixed costs, ten days saved on a project saves ten times more. The sum of project direct cost and indirect cost is called the Project Total Cost.

Normal and Crashed Cost

In the CPM cost model, there is a special emphasis on the change of the direct cost. The direct cost that is related to normal activity duration is called the Normal Cost. Shortening the duration of an activity to its crash duration usually results in higher accomplishing cost. Premium for overtime will increase the accomplishing cost of an activity. In order to shorten the activity, material costs can also increase.

The cost related to crash duration is called the Crash Cost. The nature of change of the cost can be presented this way.

Lower and Upper Limits

There is a lower time limit, the crash duration, which no amount of expenditure can shorten. There is an upper limit, which is the normal duration, and one can make no more savings by letting the task go slowly. The change of the cost between the normal and the crash time points is usually convex, i.e., the costs shortening the activity duration by a new additional day are higher than the extra cost increment of the previous shortening.

The upper cost and time limits are not actually the absolute limits but practical upper limits. An activity may cost more and take longer but it doesn’t make sense to do so. Now we are aware that there are some complex scenarios when it is beneficial to increase an activity duration but at that time it probably wasn’t known.

In the CPM cost model, a linear approximation is used instead of the convex activity time-cost curve. Using the linear approximation, the so called Сost Slope can also be defined.

Cost Slope is amount of money required for shortening an activity duration by 1 day.

In a network where an activity duration can change between its lower and upper bound, different project durations are possible. The same project duration can be achieved in hundreds of different ways. If all the activities are considered to be accomplished in their normal time, then we get the maximal project duration. If all the activities are considered to be accomplished in their crash time, we get the Minimal Project Duration. Many project durations between these two extremes can be achieved and all of them can be achieved in hundreds of different ways which result in hundreds of different project direct costs. The set of the possible solutions is shown as:

All Crashed and Normal Points

Two points of the set of feasible solutions come automatically. If time analysis is done using normal durations, we will get point ‘All Normal Points’ which is the optimal solution for cost. If time analysis is done using crash durations, we will get point ‘All Crashed Points’ which is the most expensive solution.
The initial goal in the CPM method is to identify the curve of minimum direct costs, which represents the Minimum Direct Cost Solutions.
On this curve also one point represents Time Optimised Solution with the minimum cost in the most accelerated schedule.

Cost optimised solution

If the line of ‘project minimum cost’ is defined, adding line of ‘indirect cost the optimal duration’ allows to determine ‘the least Project total cost’.

Heuristic Solutions

Original heuristic method originates from James E. Kelly and Morgan Walker was very sophisticated.

Later to make the CPM time-cost trade-off technique understandable for construction industry experts simpler heuristic method were developed by pioneers of network techniques.

First simple heuristic algorithms were presented by John Fondahl in earlier 60th. A decade later Nicolai Siemens offered an alternative simple CPM method. Both methods are based on the primary-dual theory of operation’s research. In 80th-90th some books were published where these and other methods explained and compared.

Even in recent years science papers dedicated to CPM cost model optimisation were published and can be easily found via internet search.

Early Developments

By May 1957 the CPM theory had advanced to the point where it was felt that the approach would be successful. At that time a cooperative effort to implement the method was undertaken by Remington Rand and duPont in order to determine the extent to which any further work was advisable.

Remington Rand supplied the required programs for duPont’s UNIVAC I computer located in Newark, Delaware. Engineers from DuPont provided a small pilot problem with which to make the preliminary tests. The results of this phase of the development were officially demonstrated in September, 1957. The demonstration showed that the technique held great promise. At the same time testing based on practical implementation indicated that a computer with greater capacity was essential.

First successful implementing of method was actually without calculation of cost. Time priority for the plant shutdown project (Louisville Works) was so obvious that Normal and Crashed costs haven’t been even gathered. While it was only time optimisation, the result (March 1959) was accepted as big success and soon hundreds of CPM papers were published, few algorithms were developed and deployed on to mainframe computers.

Apollo and Artemis were the first large-scale project management systems available on mini-computers (as opposed to mainframes) and the world’s first commercially successful relational database system. Artemis originated as the Artemis Project Management System developed by Metier Management Systems in 1978, a sister product to Apollo, Metier’s first PERT network scheduling system launched in 1977.

After over two decades of success Artemis encountered financial problems similar to many other high technology firms in the post bubble era but after some transformations the system still exist today under different name – Aurea Planning Solutions.

Two other systems released decades ago still used in project management and have more advanced methods then popular planning tools:

  • Micro Planner X-Pert (or X-Pert) is a project management software package in continuous development since 1979.
  • Spider Project launched in 1992 has unique methods to calculate Time-Cost balanced project and porfolio delivery plans.

Beyond original Critical Path Method

While original CPM was revolutionary it was some problems with this method that are worth to mention. Some of them creates a legacy we have to deal with even now.

  • CPM is based on preferred option to deliver project. Practically the result could be achieved more than one way. Different options may require different activities, equipment and skills, not just have different durations and costs. Complex algorithms that support ‘conditional logic’ were proposed but only a few project delivery tools work with conditions since.
  • CPM is based on assumption that required resources supply will be available. Practically we know that it is rarely the case. Projects around the Globe continue to be planned with assumption that if resource demand is identified it will be a solution to guarantee timely supply.
  • Originally network logic was based on ‘Finish-to-Start’ dependency type only. Later, other dependency types and time lags were proposed. It addresses logical issues but even further increase the complexity of heuristic algorithms.

Even development of logically correct schedule based on Normal durations is a challenge for many projects. It requires good analytical skills but planners are rarely tested on this skill. Many of them know how to use one or two scheduling tools but don’t know theory of scheduling and not able to develop feasible delivery plan that reflect reality.


  • Original CPM didn’t have an integration with risks management. Proper schedule and risk integration is common challenge for may projects now.
  • Apart from Crashing, there are other methods to accelerate project delivery but original CPM didn’t support them. Fast-tracking is the most know alternative.

The Critical Path method wasn’t the only invention in project management in late 50th. An  alternative know as ‘PERT analyses’ is based 3 point estimations was developed by the US Navy Special Projects Office, Bureau of Ordnance (SPO). In fact,  Kelly and Walker used the name ‘main chain’, and the term ‘Critical Path’ was invented and promoted by the team developed the PERT (Program Evaluation and Review Technique).  By the late 1960s both CPM and PERT had merged into ‘Network based management systems’. It is a separate intersting story.

Alex Lyaschenko

PMO | Portfolio Planning & Delivery | PMP | P3O Practitioner | AgilePM Practitioner | Six Sigma

Six Steps of Success Driven Project Management

Six Steps of Success Driven Project Management

Step 1 – Define integrated project success criterion

With multiple success criteria decision-making is complicated – increasing one of them, we may decrease another. There is a need for some weighting factor that may be used for decision-making. It is necessary to be able to measure overall benefits of projects and portfolios, to be able to compare options and to select the best management decisions. It is important to define the integrated criterion of the project/portfolio success (or failure) and use it as the optimisation criteria when the project delivery plan is calculated.   

One of the potential approaches is to use money for measurement of everything.

For example, defining the cost of one day for project acceleration and delay we will be able to estimate if it is profitable to pay more for faster performance and if project performance was successful if it was late but saved certain amount of money.

Step 2 – Create optimistic project schedule model

Project delivery model is developed with optimistic, expected and pessimistic estimations and all identified risks are integrated into the model.    

Optimistic model is based on optimistic estimates of all project parameters and includes only most probable (90% probability or larger) risk events. This model is used for setting performance targets for the project delivery team. It is clear that optimistic targets will not be achieved but using other than optimistic version creates hidden contingencies that are likely to be consumed. (Parkinson Law)

Performance targets shall not include contingency reserves or they will be lost. 

Step 3 – Simulate risks and set reliable targets for project management team

Project management team shall have time and cost buffers for managing project risks and uncertainties. Project or phase buffer is a difference between target value and the value for the same parameter in the optimistic schedule. Targets shall be set using risk simulation. These targets shall have reasonable probabilities to be met (usually in 70-80% probability range). Project and phase targets and buffers may be created not only for the integrated project success criterion but also for separate parameters like project cost and duration. Probabilities to meet project/phase targets are called success probabilities.


Step 4 – Set project sponsor targets

Management reserve for unknown unknowns is usually created basing on past performance data. When these data are missing or not reliable project sponsor targets are set using the same risk simulation model but with higher probability to be achieved (usually in 90-95% probability range).
So project has a set of targets – tight targets for project team, reasonable targets for project management team that include sufficient contingency reserves, and more comfortable targets for project sponsor that include additional management reserves.

Step 5 – Estimate buffer penetrations

It is natural that project will be late to optimistic schedule and project/phase buffers will be penetrated in the process of project execution. It is necessary to be able to estimate if these buffers are still sufficient and if project performance was better or worse than expected. The natural way for estimating buffer penetrations is calculation of current probabilities to meet the targets. If new probabilities are higher than initial project performance was better than expected though success probabilities depend not only on internal factors. If project performance was perfect but new risks were identified success probability may become lower because initial contingency reserves did not consider these new risks.

Step 6 – Analyse success probability trends

Current success probabilities show project status but project status information is not sufficient for decision making. Decision-making shall be based on the analysis of project trends.
If the probability to meet project target is rising then project buffer was consumed slower than expected, in other case project buffer was consumed too fast and project success is endangered. Management decisions shall be based on the trend analysis. Even if current status is good (success probability is high) but the trend is negative corrective actions shall be considered.

Success probability trends are the best integrated performance indicators – they take into account project risks, and they depend not only on performance results but also on the project environment changes.

Alex Lyaschenko

PMO | Portfolio Planning & Delivery | PMP | P3O Practitioner | AgilePM Practitioner | Six Sigma

Missing Part of Project Management Triangle

Missing Part of Project Management Triangle

Project Management Triangle (also known as Golden Triangle or Iron Triangle) has one missing part.

Originally, when the triangle was developed, the missing part was so obvious that the author didn’t include it in the triangle.

“I was thinking about how time control could be integrated with cost control. This was the main plank of my research (1959). I designed a computer program which did integrate cost, time and resources and could show the effect of decisions about the work and how to do it on both cost and time simultaneously.” (HOW IT ALL BEGAN, PM World Library, 2006, Dr. Martin Barnes)

The CPM method was invented (1957) as an attempt to understand how resource assignments impact project Time and Cost, but soon it was realised that the third component, quality, is also very important.

“…you did not just have to manage the cost and the time, you had to manage the delivery of what was specified as well. I sketched a diagram to make the point – a triangle with time, cost and quality at the corners. On the overhead projector, I moved a coin around the triangle to show how the three tensions competed, etc. This concept really caught on and, as far as I know, it was the first time anybody had set down that managing what we now call a project was not just time control, it was control of cost and outcome as well.”

‘Resources’ is the ultimate base of the Project Management Triangle.

The triangle is NOT ‘How Time, Cost and Quality impact each other’ but ‘How changes in Resource assignments impact Time, Cost and Quality.”

An alternative version of the triangle with “Time, Cost and Scope” was developed later, but it is a different story…

Alex Lyaschenko

PMO | Portfolio Planning & Delivery | PMP | P3O Practitioner | AgilePM Practitioner | Six Sigma

Multiple dependencies between two activities in Microsoft Project

Multiple dependencies between two activities in Microsoft Project

Myth: Ladder Scheduling is impossible in Microsoft Project as it does not allow two dependencies between two activities.

Some business processes require the creation of multiple dependencies between two activities. Particularly, sometimes activities could be performed in parallel but the successor activity can be executed with a defined delay from the predecessor. It is known as ‘Ladder Scheduling’.

As Microsoft Project only supports a single dependency between two activities there is a popular myth that it is not possible to link activities multiple times. A simple workaround allows solve the challenge.

Ladder Scheduling (Start-to-Start plus Finish-to-Finish dependencies) could be realised by adding an additional dummy milestone. It is inconvenient, but possible to get multiple links.

Ladder Scheduling in Microsoft Project:

Saying that it is not the best practice to create SS + [duration lag] and FF + [duration lag] dependencies, as such an approach may cause hidden planning issues. When the predecessor activity commenced but the required volume hasn’t been achieved, the schedule incorrectly shows that the successor activity can start. Alternative approaches were discussed in these posts:

Point-to-Point Dependency

Volume lags


Alex Lyaschenko

PMO | Portfolio Planning & Delivery | PMP | P3O Practitioner | AgilePM Practitioner | Six Sigma