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Uncertainty in schedules

24 replies [Last post]
Mon, 2002-07-08 07:21
Tomas Rivera
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I am going to raise a subject that was touched during another discussion thread in this forum. I thought it deserved special attention.
How many of you feel the information contained in your schedules is uncertain or incomplete and cannot represent your project nature?
How often does it happen to you that the actual chain of events or activities taken place in a project differ greatly from what you anticipated in your schedule?
How often do you feel your schedule cannot handle or manage so many changes or unforeseen events?
Have you had sometimes projects which are so chaotic or complex that you feel you can not schedule properly?
Do you sometimes feel you cannot give the project managers a good plan/schedule to manage the project?
By the way, I am posing these questions from the point of view of construction projects.

Thank you for your comments
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Sun, 2003-01-05 17:39
#1
Tomas Rivera
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Ali:

I agree with you completely, especially when you say "if every thing is well defined and determined before starting execution, the gap between realistic and unrealistic program will be decreased".

I would like to add to your comments that the standardization you are talking about, to me it is good Project Management practices. For example, when you say who is going to be responsible for what, I would look for a couple of documents: The Work Breakdown Structure, the Organization Chart and the Responsibility Assignment Matrix. If we are applying good project management, these documents ought to be defined.

Tomas Rivera
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Sun, 2003-01-05 15:43
#2
Ali Hamouda
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Mr.Tomas:

I always beleive in the process of Standardisation,that it can solve alot of problems,and if we could apply standards from the start of creation of the Model or the Plan
for example:

-each part of the plan whom is going to make such as desgin ,procurment stage.
-each part of the construction civil,mechanical,elect..etc.
-testing and commissioning.
-revewing and feedback,,who will be involved,,,,,

if every thing is well defined and determined before starting execution, the gap between realistic and unrealistic program will be decreased.

for sure it will not be 100% perfect but at least we will have control upon what is in our hand.and at this time no one will tell the Planner "it is not my Job, search about some one else!"




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Sat, 2003-01-04 16:48
#3
Tomas Rivera
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Dear Forum Guest:

I would not say that your are off base with respect to this site being a construction site and your area of work being mining. To me, mining operations are construction operations. Excavation, fragmentation of rock, tunneling, loading and hauling, access roads, water table control, etc., are construction operations. If your business is very risky, maybe you should use risk analysis software. Or at least, allow some contingency time at the end of your project schedule and/or at the end of selected activity paths.

Tomas Rivera
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Sat, 2003-01-04 15:21
#4
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Other people have used "interesting" to describe the discussion thus far, so, instead I will say that I find it fascinating!

Coming newly into the scheduling arena, with only two years of P3, and implementing it in the "natural resource" extraction field, I had made statements to imply that my life would have been a whole lot easier had I been in the construction side of things (where everything was so deterministic and/or probabilities could easily be assigned to take care of things). Looking at activities from where I sit, I thought the construction sector has had scheduling nailed to an art. Following this forum is obviously revealing otherwise for me.

In my sector (Mining), those feelings expressed by Ali and the questions raised by the originator of the thread have been experienced. In the tail end of my second year into this adventure, I have come to realize that the issue is as much a monetary as it is a people one. When I got started, only "upper management" had bought into scheduling - as it showed them what lies ahead. But there was so much "static" from the executors - as they saw the matter as a "top-down thing"; not only shoved down their throats, but that someone might hang out to dry when it is all done. This mentality is currently being addressed through education and training. And the building of a schedule; the information (quantities, durations, logic or sequence, resources and their availabilities ...) that goes into network is partly "owned" by the executors of the project.

I am currently at the point where, with a great deal of uncertainties associated with the data being used, I need to determine "goodness" of the data. Because it is a highly risky business, to start with, the level of accuracy in information becomes very important; and I need to determine implications of failing to meet targets, if I had three options of which path to follow, and they all look critical, which one to pick.

I was move to contribute even though the thread was clearly "marked for contruction only", as a result I feel I owe group an apology - especially if you found me "off-base".

IDM
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Thu, 2002-07-25 08:23
#5
Tomas Rivera
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Colin Fish:

Monte Carlo for Primavera has probabilistic successors and conditional successors branches.
Regarding Design/Build construction projects, I have worked in several projects of this type. The quality of the information determines the quality of the schedule. Same thing as for cost estimating. When you have preliminary information you develop a preliminary schedule (with its corresponding risk). When you have detailed information you can have a detailed or less risky schedule. When I move from preliminary to final schedules, it usually happens that part of my general logic does not hold true. This is due to the fact that we made assumptions when we had preliminary information and did not know what the final condition or characteristic was going to be. I make clear at the start of this process the quality of the information I am producing and that is the way it should be regarded.

Tomas Rivera
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Thu, 2002-07-25 12:52
#6
Colin Fish
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Sorry Tomas in the UK D&B is a commonly used abbreviation of Design & Build.
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Wed, 2002-07-24 07:42
#7
Tomas Rivera
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Mike:

Input from key members is something very desirable and many times it is a must. This is the ideal arrangement; but it is not the only way to achieve success. There are other ways, but difficult to implement. I have been in several projects that have been very successful and one of them a model for the mexican construction industry, in which there were no participation of any team member except for isolated pieces of information. The type of management has to be a special one for this to work.

Tomas Rivera
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Wed, 2002-07-24 07:32
#8
Tomas Rivera
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Colin Fish:

Excuse my ignorance; but, what are D & B projects?
Are they Design and Build construction projects?

Thanks

Tomas Rivera
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Wed, 2002-07-24 01:44
#9
Colin Fish
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This is a very interesting discussion. However, there has been no discussion so far regarding programme logic.

I am a firm believer that the key to producing an accurate programme/schedule revolves around inserting correct logic into the critical path. Referring to the law of diminishing returns, the overall programme period will be determined by 20% of the operations. These will be the items on the critical path and, whilst the other 80% will have an impact if their float period is taken up, provided careful attention is taken working out the duration and logic of the important 20%, the plan should be accurate.

The problems I have in producing schedules are that very little information is available at the front end of the project (I work predominantly on D & B projects). The durations of operations can be calculated to some degree of accuracy but the logic is often the area of uncertainty as the project is still in the designers head and my programme relies on my experience to determine what will happen when.

I have used risk Analysis software (Pertmster v7) and this does not account for fundamental changes in sequencing.
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Wed, 2002-07-24 01:44
#10
Colin Fish
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This is a very interesting discussion. However, there has been no discussion so far regarding programme logic. I am a firm believer that the key to producing an accurate programme/schedule revolves around inserting correct logic into the critical path. Referring to the law of diminishing returns, the overall programme period will be determined by 20% of the operations. These will be the items on the critical path and, whilst the other 80% will have an impact if their float period is taken up, provided careful attention is taken working out the duration and logic of the important 20%, the plan should be accurate. The problems I have in producing schedules are that very little information is available at the front end of the project (I work predominantly on D & B projects). The durations of operations can be calculated to some degree of accuracy but the logic is often the area of uncertainty as the project is still in the designers head and my programme relies on my experience to determine what will happen when. I have used risk Analysis software (Pertmster v7) and this does not account for fundamental changes in sequencing.
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Tue, 2002-07-23 09:20
#11
Mike Harvey
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Unless there is ’total buy in’ of the programme/schedule by key staff on the project the programme is only notional in the planners mind.

Programming/Scheduling is pre-engineering of the project process and will only achieve success with input from key members.

Mike Harvey
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Tue, 2002-07-23 03:55
#12
Colin Cropley
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This has been the most valuable and interesting discussion I have seen in these forums.
Thanks to all who have contributed, especially Tomas who started it and David who introduced me to the Lean Construction site and the work of Ms Poppendieck.
The results of planning will reflect the old axiom: What comes out depends on the quality of what goes in (in a negative sense "Garbage in=Garbage out").
I am inclined to believe that unless we are forced to consciously think about the (often many) factors influencing task duration outcomes, and define optimistic, most likely and pessimistic durations, we produce schedules that are misleading. Misleading in the sense that a single, deterministic duration for most projects involving hundreds or thousands of tasks and interdependencies, is highly unlikely to be right (within a few percent of the final project duration outcome). Risk analysis forces us to face the reality that most of the information we receive is uncertain.
Even if we (or those who provide schedule information) are able to nominate optimistic, most likely and pessimistic durations, how do we know what the probability distribution(s) of those durations are? Triangular is simple, but surely a simplification.
In the end, I would suggest that the law of diminishing returns or the Pareto principle apply: 80% of the benefit is obtained from the first 20% of the information we can obtain. The schedule information is usually going to be quite uncertain, so agonising about what are the precise minimum or maximum durations, or what is the true shape of the probability distribution is likely to be less productive than running the analysis, getting the resultant time and cost project completion distributions, analysing the implications and managing the project to minimise the risks.
One major benefit could be to focus on those tasks with a high probability (say >90%) of being on the critical path and devising ways to minimise their durations.
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Mon, 2002-07-22 10:23
#13
Tomas Rivera
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David:

I think most, if not all, planners make all those kind of decisions you mentioned. These unconscious/conscious decisions are generally not made in a structured or formal way. Therefore there is a mixture of optimistic/pessimistic/in-between duration estimates during schedule development, probably they tend to be pessimistic if the project timeframe allows it. If not, we will have to use optimistic durations. If we do a risk analysis using PERT durations we could identify the risk involved in the schedule paths. And, if this is one of the things your are doing when you do your risk analysis, then you should have the information of why your project was finished ahead of your risk analysis predictions. You can look at the PERT durations (3 durations per activity) vs the actual durations and vs the CPM duration (one discrete duration) and find out how they behaved. From this analysis you can answer your question.
Am I right?

Tomas Rivera
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Mon, 2002-07-22 09:42
#14
Tomas Rivera
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Luis:

I went through the links you provided. They present a concept that deserves a serious look. There are a couple of things I think should be done about it. But, as its authors say, it still needs research and to be fully developed. Nevertheless, it has a sufficient level of maturity to start implementing it on a project.
Thanks,

Tomas Rivera
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Sat, 2002-07-20 01:23
#15
Luis Silva
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Good Thoughts fellows.... Very good knowledge sharing.

The Lean Construction Institute has raised o lot of those issues in its publications, and somehow has some answers to your questions. The bottom line is to make quality assignments pulled from our Master schedule plan for our lookahead planning cycle, and commitment on results of all participants of the project.
I will suggest some literature that could help us to have better results on our schedules:

1- Simple introduction to the topic:(http://www.poppendieck.com/construction.htm)

2-Good summary of Last Planer Technique:(http://www.leanconstruction.org/pdf/LastPlanner.pdf)

2-Suscint presentations about lookahead Planning by theory of constrains and influence of variability in construction process(http://www.leanconstruction.org/pdf/ASCLCI2.pdf)

3-Visit the lean construction web site, there are a lot of good information there (http://www.leanconstruction.org)

PS: Make it work. Researchers give us some answers but depend a lot on ourselves for practical usage and field implementation....

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Thu, 2002-07-18 03:02
#16
David Bordoli
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Thanks for raising this topic - a good discussion has followed.

I would like to canvass some opinion:

Lets say that most programmes are not risk analysed, they have a single duration for each of the tasks. When calculating (guessing?) the task duration do you think the planner is making any subconscious decisions about that duration? For instance do you think:

1. we are naturally optimistic and maybe underestimate task durations?
2. do you think the duration we chose is the mode/mean/median?
3. do you think the duration represents some higher confidence, say that we are confident it will be completed within that duration in 95% of cases?
4. or something else?

This interests me as, whilst many construction projects finish later they never seem to be quite as bad as some of the predictions that risk analysis makes. This leads me to think that we subconsciously (or even consciously) assess risk as we calculate task durations.

Many of you will know that I use Asta Development’s TeamPlan (www.astadev.com). Their risk analysis package is an add-in module and costs 100 GBP. I reckon that is quite good value, it only has basic functions but I think we in the construction industry even struggle to comprehend them!

I look forward to all your thoughts!
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Mon, 2002-07-15 04:26
#17
Colin Cropley
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This is a fascinating topic and Tomas has done us all a favour by raising it.
Someone said "A plan (in itself) is useless, but planning is very important." So planning is a process that should represent the efforts of stakeholders in a project to model the way the project is to proceed in the most accurate way possible, with the planner being the means of expressing the model. At its best, it is an iterative process, where those involved are invited to review their part of the plan, with strong motivation to do so, providing timely feedback to the planner to revise the plan and re-issue it for further review. In this way, the team should converge on the best possible model of what is to happen.
I agree that it is vital to have the commitment of management (the real decision makers and exercisers of power), to encourage, but if necessary, coerce the stakeholders to provide or at least review and sign off their part of the schedule. Management can require design, procurement, fabrication, construction and commissioning managers/ supervisors/ team leaders to be accountable for their part of the plan with rewards or penalties following good or poor modelling, as applicable.
It is not necessarily about money, although I agree that this is a powerful motivator.
So management can make a huge difference to the level of participation by stakeholders in schedule development.
To summarise an earlier contribution "Involvement leads to commitment". Even if your ideas were not necessarily included in the schedule, if you know that your contribution was seriously considered and you received feedback about it, you are much more likely to commit to the schedule than if you had no part in its development.
Of course, all this is impossible if the schedule is being developed while the project proceeds and there is no time to consult properly. The plan then becomes the kind of uncertain exercise Tomas first discussed.
This is another compelling reason for allowing enough time at the start of a project for proper planning: lack of commitment to the plan if it is not developed with consultation.
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Mon, 2002-07-15 02:23
#18
William Stakelin
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I think the nail was hit right on the head. It is all about the money. If there is a bonus/penalty issued within the contract documents people will respond.

Everybody involved in construction are there for one reason, Money! Everyone loves to make it and everyone hates to lose it.

It is this motivation that can drive a project when other means fail.

I think it would be wise of the Owner/Architect to include a Bonus/Penalty clause in the contract if time constraints are important.

Money makes people do things that they otherwise would not.

William Stakelin
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Sat, 2002-07-13 11:00
#19
Tomas Rivera
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Ali:

I am going to comment on your reply assuming we have a good schedule that resembles the true nature of the project on hand. Otherwise, we would have other set of comments.
You are talking about understanding (by the team) what is a schedule, how it should be used, how it should be regarded, what importance it has on the project and the responsability of everyone around it. In order to get to this level of understanding we need to have those things clear in our minds and help our team understand (because we are suposed to be the experts).
Are we in a project where the schedule should be the one thing most important, or is it something else? If it is something else, the schedule is going to be kicked around. But, if we are in a project where you have $10,000 dollars of penalty for each day the project is delayed, and we have a bonus/penalty plan for our subcontractors and site people, everybody is going to turn their heads to the schedule. At this moment you become the star of the movie and you’d better be ready.
See how the attitude changed? With this new attitude everybody will be asking about what the schedule says, will be asking about list of activities, float, critical activities, dates, schedule reports in diferent formats, updates, etc.
Now we can ask the same questions that you mentioned in your reply:
You feel there is no control in the site?
You feel you are acting as a recorder instead of telling what to do?
People are not convinced of what is in the plan (the only plan)?
Do we need to train people to understand planning?
Probably we need to address all of the above, but you get my point? It is about management, mainly human resource management, which sometimes we do not know how to go about. I have said many times: often the problem is not technical, is human.
Again, I am assuming we have a good schedule and a good implementation plan for the schedule.

Tomas Rivera
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Sat, 2002-07-13 10:24
#20
Tomas Rivera
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Ernesto:

I agree with you. I think the people who is going to execute the job should be involved in the development of the schedule. This way the site people will not feel that a schedule is imposed upon them, but that they are executing "their" schedule.
Sometimes this is not possible to some extent because the time, coordination and effort required by a team of people to agree on a schedule, starts to get out of hand. I have been involved in projects with large schedules developed by myself where the contractor had to have a military type of environment to enforce them. Otherwise you have to make a lot of effort for buy-in when your schedule is being implemented. One thing is for sure in my experience: you have to have the support of upper management.

Tomas Rivera
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Sat, 2002-07-13 09:55
#21
Ali Hamouda
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Dear,

Yes you are right in most of your quesitions.
Always I feel that there is something missed in the sechedule,and there is no control about what is happening in the site and what is in the schedule.

IN some of my projects I was having the feeling that I am working as a recorder(recording what is happening in the site), In spite that the main Job of a Planner is to tell the people what to do..and Not the Opposite.

the site people them selve are not convinced by what is in the Plan.Do we need to train the people to understand planning?

Un realistic program.Is it the problem of the Schedule or the problem of the feed back?.But we know that the target plan will never match the actual case of any project.

Do you sometimes feel you cannot give the project managers a good plan/schedule to manage the project?
Yes in most of the cases ,the plan is only aguide or limitation for the project mangers so as not to go outside this limitation.But the plan is a good guide for the mangers and not a good schedule to manage the project.

Finally,, I feel that we still in the first step to acheive the perfiction..but I beleive that we can.
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Sat, 2002-07-13 04:51
#22
Ernesto Puyana
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I have to say I have experienced all those feeling, and not necesarily in a very large or complex project. But on the other hand, I’ve also felt the feeling of satisfaction and power derived from a well planned project, executed exactly as scheduled.
What made the difference? I give a lot of weight to the involvement of the people in charge of the job, on it’s planning and scheduling. Somebody else’s schedule means nothing to those guys who think they know it all, and "fly by the seat of their pants".
When I have acted as an external scheduler who reports to a field superintendent, I’ve always felt wasting my time.
Even if the project is risky or complex, the field people’s comittment to their plan makes the difference.
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Fri, 2002-07-12 07:33
#23
Tomas Rivera
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Colin:

Thank you for the information. I am aware of those type of resources. I myself own Monte Carlo by Primavera. But my question was how many of you felt the way I described in my first post. And I am refering to using CPM and not yet any risk management software.
If some of you feel this way often or just sometimes, it could have the following reasons:
1.- A legitimate amount of risk or uncertainty in the project (which takes us to using a risk management software).
2.- The need for better ways to understand the nature or behavior of projects.
3.- The need to improve our ability to represent projects in a CPM schedule.
4.- The need for better tools or methods to help us understand or represent a project in a model.
5.- Some other reasons there might be.

Tomas Rivera
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Fri, 2002-07-12 02:20
#24
Colin Cropley
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Tomas
Where there is significant schedule uncertainty, it is a good idea to use a scheduling tool that can take risk (ie, uncertainty) into account. I recommend you look at a product called Pertmaster V7 (www.pertmaster.com, a British cost & time risk analysis tool from a Primavera Partner that works with P3, SureTrak, P3e & MS Project. I have recently done an evaluation of Risk using P3, P3e & Pertmaster and presented it to the local Primavera User Group in Victoria (Australia). You can find that presentation (a Powerpoint sllideshow) plus screen dumps from the three applications at http://www.anzpug.org/regional_groups/regional_victoria_main.htm.
YOu have to put minimum, most likely and maximum durations against each activity with uncertain durations, plus % probabilities against activities (& activity paths) which may or may not occur. The Pertmaster software then runs the schedule 1,000 times, assigning random durations and branching choices (according to the probability distributions you have selected), using the Monte Carlo mathematical technique, similar to that used in Primavera’s own Monte Carlo software (Pertmaster is much more usable).
The result is a distribution of time of completion of the schedule, plus a cost distribution if the schedule is resourced and costed.
With the resultant information, you can forecast, for example, that there is a 95% probability that the project will be finished by a particular date, or a 90% chance (you can specify the percentage) that the project will cost no more than a particular amount of money.
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