(1) Explain your problem, don't simply post "This isn't working". What were you doing when you faced the problem? What have you tried to resolve - did you look for a solution using "Search" ? Has it happened just once or several times?
(2) It's also good to get feedback when a solution is found, return to the original post to explain how it was resolved so that more people can also use the results.
Hi Mr. Stephen Devaux, Mr. Rafael Davila and Mr. Mike Testro
I read the “Critical path Quiz” posted on the PP on Wed, 2011-07-20 16:05 by Mr. Stephen Devaux. It was really a valuable discussion for new planners like me. I saved that in (copy past) in MS Word and studying that and calculated manually and that was correct. The term “DRAG” is new for me and a bit confused with it or maybe I misunderstood that. I believe you can guide me batter if I tell you a bit about me, I am (partially) involved in planning with Electrical and instrumentation back ground since 1998 using MS Excel (In Pakistan), learned MS Project in 2002 (Pakistan), Primavera in 2004 (Saudi Arabia), but worked as a full fagged planning engineer in 2009 in Dubai UAE where I made plans for three commercial towers of 3B + G + 3P + 20 typical floors including MEP and also done delay analysis for one of them, prepared an EOT claim of 150 days and got that approved by the client, and now I am working as Sr. planning engineer in Qatar. It’s quite true if I say that I have just 3 years of experience in project planning. Now;
May these questions be silly for you, but sir, that would a great favor if you award some of your time to me. You can use my personal email tanveeraniazi@yahoo.comif you like.
Thanks and Cheers
Tanveer
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Hi Mr. Davila
Thanx for understanding me. I am studying the stuff of Mr. Stephen Devaux and hope you and him will clear all my doubts/points if I have at the time.
Cheers and Thanx
Tanveer
Tanveer,
I am using Spider Project.
About DRAG concepts after you study Deveaux papers you will find the concept is easy to understand.
Long ago some schedulers and developers interested on the subject developed sophisticated algorithms for what they called time-cost trade-off. It would help not only for crashing and knowing the cost of different job durations but also to determine the theoretical optimum job duration that never happened. It was computer and scheduler time consuming, and maybe did not considered resource leveling. With DRAG concepts you keep a good vision for your management decisions that are difficult, if not impossible to model with time-cost trade-off methods.
Unfortunately too much attention is paid to the creation of your schedule but little to the maintenance of the schedule.
Many schedulers believe updating a schedule is merely plugging in actual, the more lazy only plug in a single start and finish date for activities that have been disrupted by Owner actions as well as by their own, this makes very difficult to apply and sustain measured mile concept in disruption claims. Others spent time with Statistical and Monte Carlo methods only at the initial stage of the job and do not use the method to keep the probabilities of meeting target dates at an adequate level.
With Statistical and Monte Carlo methods you can analyze the probabilities of finishing on time for different scenarios, but it comes at a cost, DRAG cost can again be of help.
There are many ways to skin a cat, there are many ways to crash a schedule.
Best regards,
Rafael
Rafael wrote:
"DRAG is a valuable metric but it is not the absolute answer, usually a combination of alternate plans plus some crashing on the alternate plan using DRAG concepts gives you better results."
Of course. Also, DRAG has application far beyond simply compressing a single schedule. As just one example, companies that are multiprojected and sharing resources across a portfolio should be tracking DRAG and DRAG Cost and tying them to the individual resources that are causing the DRAG (i.e., those that are winding up on the CPs of project after project). The DRAG Cost then gets tied to the individual resources on those activities and becomes the justification for hiring more of those resources. Through ABCP analysis, for example, the organization can see that over the past year, on 17 projects, the DRAG Cost of activities that used mechanical engineers was $8.4M, and much more than for any other resource. All else being equal (which would require further analysis!), this probably suggests that recruiting more mechanical engineers might be a good idea.
This is just one example of how DRAG can be used in other arenas, such as staffing. As you say, Rafael: "No matter what, the more informed you are the better."
Fraternally in project management,
Steve the Bajan
Hi Mr. Davila
Thanx for the precious guidelines. BTW which software are you using? Also I didn’t understand “soft logic”, if you please further define that. Your advice is valuable no doubt, but sorry to say a little bit of compact sort of thing. That’s a bit difficult to understand for a new planner like me. Anyway thank you very much for guiding to a success of planning profession.
Cheers and thanx
Tanveer
Tanveer,
DRAG is a valuable metric but it is not the absolute answer, usually a combination of alternate plans plus some crashing on the alternate plan using DRAG concepts gives you better results. At times the schedule must be revised by adding activities, changing soft logic, adding additional crews, adding shifts etc. Within these alternatives the use of DRAG concepts is also valuable especially if the initial alternate plans still require extra compression.
My software calculates DRAG but I do not believe it can be computed by other software with simple formulas or global changes. DRAG cost can be calculated using formulas or global changes very easily if a linear function and stored on a user defined field. Still some management decisions shall be made because not always the activity with lower DRAG cost is the best option.
Contractors usually have a good sense of what activities have lower DRAG/Crashing costs without even recurring to the actual math, without knowing the term Drag, but frequently it is all about available drag as they know after some compression of a critical path other path will become critical and any further compression of the now non critical path is a waste.
No matter what, the more informed you are the better.
Best regards,
Rafael
I'm a West Indies cricket fan myself, Tanveer. We've fallen on hard times in the past 15 years, but we'll be back! (I saw part of Hanif Mohammed's second innings 337 at Kensington Oval in 1958, perhaps the greatest Test-saving performance of all time!)
"This term is really new for me. Before posting my thread, I discussed that with a friend of mine who has about 9 years experience in planning but he said that he didn’t know about it and haven’t heard of that before."
If people like Vladimir Liberzon and Rafael Davila (two of the most knowledgeable scheduling people I've ever met) had never heard of DRAG before, you know it's new for everybody! And it's so absurd because every software package (and every planning student!) knows how to calculate both total float and free float. But float is always off the critical path! And what is more critical: the critical path or NOT the critical path?? And all that the software (Primavera, Asta, etc.) tells you about critical path activities is zero -- that the float is zero! (More or less, if we want to get fussy about it.)
The project is as long as its As Built Critical Path. So if want to compress the schedule, we need to quantify the time impact of critical path activities -- and that's all that DRAG is. And that recognition is why Vladimir programmed DRAG into Spider Project.
"As a matter of fact, my present and the last job (that first joined as a full flagged planning engineer in Dubai) are the result of discussing the matters with the same friend, the PP forum, and the comments of Mr. Rafael Davilaand Mr. Mike Testro. And I should pay special thanx to Mr. Mike Tastro who helped me in analyzing the delay occurred at my last project in Dubai. I worked on his directions and made an EOT claim and the client had approved that."
That's why PP is such a great forum. You're not going to run into Mike Testro's experience in construction and forensic scheduling elsewhere (and his moderating has been of huge benefit to what used to be the chaos of PP forums!). I wish that Mike would recognize the potential benefit of DRAG computation to forensics, but hey -- maybe you will, Tanveer!
BTW, if you read the Bill Duncan article, Scheduling is a Drag!, I'd recommend the Defense AT&L article The Drag Efficient next. It shows how to compute DRAG in a simple network and begins to get into what you were discussing, the cost of DRAG. Then the other articles put DRAG and DRAG Cost into the rest of the TPC framework, managing projects as investments.
Fraternally in project management,
Steve the Bajan
Hi Stephen,
Thanx again for your valuable suggestions, I haven’t go through all those links so far but I already read "Scheduling is a Drag"and studying it again in the frame of your comments. As soon as I read all of it I will come back to DISTURB you. This term is really new for me. Before posting my thread, I discussed that with a friend of mine who has about 9 years experience in planning but he said that he didn’t know about it and haven’t heard of that before.
As a matter of fact, my present and the last job (that first joined as a full flagged planning engineer in Dubai) are the result of discussing the matters with the same friend, the PP forum, and the comments of Mr. Rafael Davilaand Mr. Mike Testro. And I should pay special thanx to Mr. Mike Tastro who helped me in analyzing the delay occurred at my last project in Dubai. I worked on his directions and made an EOT claim and the client had approved that. Now you have been my fourth guide in project planning. And I am sure I am gonna be good planner very soon.
Yes, I am from Pakistan. Not really a fan of cricket, but don’t miss it when Pakistan playing with India or Australia playing with anyone.
CHEERS
Tanveer
"I will really be glad if you refer me some links or books at the topic."
There's an old saying, Tanveer: "Be careful what you ask for in life, because you may get it!" When you get around to reading my post, you'll see that I referred nine articles, two webinars, and a book!
BTW, you said you lived in Pakistan. Are you a cricket fan? The upcoming England/Pakistan series should be interesting...
Fraternally in project management,
Steve the Bajan
Hi Stephen,
Thanx for the reply and much more thanx to encourage me telling me that these questions are not silly. I’ll read the reply latter coz I will get late for my office if I start that now. I will really be glad if you refer me some links or books at the topic.
Cheers - Tanveer
Hi, Tanveer. How are things in Doha? (I spent a good deal of time there about a decade ago, teaching seminars for Qatar Telecom).
Actually, your questions are excellent. They are, in fact, the sorts of questions that usually come up when someone knowledgeable about PM first discovers DRAG, or other TPC concepts. I’ll try to answer you specific questions below, but first I’ll point you to some articles and other resources about TPC:
A six-part series on Total Project Control methods and metrics, published in ProjectsAtWork on-line-magazine, Oct-Dec 2006 (you have to register to read them, but it's free):
A couple of webinars for the Project Management Institute, that have been archived and that you can order from them:
And my 1999 book:
Critical path DRAG is just a small (though important!) part of the whole Total Project Control approach, which emphasizes that projects and programs are investments and must be managed as such. TPC is “total” because it quantifies all three sides of the traditional Triple Constraint Triangle (SCOPE/TIME/COST) into trackable metrics (the DIPP and the DIPP Progress Index or DPI) that, primarily, focus on how the “profit” of a project is affected by changes in scope and acceleration or delay of schedule (perhaps due to resource changes).
So to try to give brief answers to your questions:
1. If DRAG of an activity is the amount of time by which it shares the total duration of the project, then, in the quiz, the DRAG of the critical path is 95 and the duration of the project is 160, what else contributing the remaining 65 units of time.
To be truthful, I’m not sure exactly what this means. DRAG, like float, is intended to be analyzed on specific activities – how much is THIS activity (or constraint or resource bottleneck) adding to the project duration? I’ve never been able to discover much benefit for adding DRAG up across a whole project schedule. But if you think of some value to summing it at the project level, I’d be interested.
2. Again, If DRAG of an activity is the amount of time by which it shares the total duration of the project; does this mean that we cannot or not logical to crash the schedule by less than the DRAG (of the baseline program)?
Compressing the schedule makes sense when, by doing so, you make the project a more valuable investment. Thus decreasing an activity’s DRAG from 20 days to 10 days by spending an additional $50,000 makes perfect sense if each day you deliver earlier increases the “project profit” by $6,000/day (or more, of course). (Or, indeed, reduce LDs by more than the cost of the resources.)
3. Is that always necessary to calculate DRAG before proceeding to a crash?
No, but calculating DRAG allows you to focus on the BEST activities to shorten in order to gain time. Schedulers sometimes spend a lot of time trying to shorten a CP activity of 20D duration that may only have DRAG of two days. They would probably be better off focusing on an activity that may only have a duration of 7D but that has a DRAG of six days!
4. What if we need a crash of more than the DRAG?
If you compress the duration of a 25D activity that has 5D of DRAG to 15D, now the activity is no longer on the CP. Instead, it has 5D of float. Now, to continue schedule compression, you need to look at what has now become the new CP and what the DRAGs of its various activities are. And so on, iteratively, until the schedule is where you want it.
5. What about the financial impact? Shall we ignore the LD and cost of Delay Penalty and proceed with schedule crashing?
6. How can I calculate the DRAG cost?
DRAG Cost is a hugely important subject! (After all, projects are investments!) For one thing, DRAG Cost is how you justify the additional resources on an activity to make its DRAG go away and shorten the schedule! And sometimes, as the sidebars in the above Defense AT&L article demonstrate (but true in many projects, from pharmaceutical and health care to emergency response and digging water wells!), the DRAG Cost can be measured in human lives and suffering as well as dollars.
But DRAG Cost is also a very complex subject, far more than I can answer here, so I urge you to read the above literature.
7. I am using Primavera (P6v7), how can I calculate the DRAG when I have a couple of thousands activities (10614 to be very accurate) in my program (not prepared by me)?
Sadly, Primavera does not compute DRAG. Complain to Joel Kopelmann (CEO) or Richard Faris (second-in-command) about it, if you want. Or better still, switch to Spider Project, which does compute critical path DRAG. It’s absurd in this day and age that schedulers should have to work with software that does not provide the most important (critical?) CPM metric, telling them how much time each activity is adding to the project duration (and how much that time is costing).
8. How can I (or my PM) do batter with the project if I (or PM) know the DRAG of the schedule (what is benefit of knowing the DRAG)?
If you aren’t computing DRAG to optimize a schedule at the start of the project, that’s one thing. But wait till your schedule starts slipping and you’re desperately trying to figure out how to recover! That’s when DRAG becomes hugely important, to show you where the best places are to go to pull in schedule, and when you’ve done those, where to look at next.
I think the publications above will help you considerably. But there’s one more thing that might help: there is an add-on to MS Project 2007 & 2010 called the Sumatra Project Optimizer at: http://sumatra.com/projectoptimizer/projectoptimizer.htm
With the free trial download, they used to have (I don’t know if they still do!) a walkthrough document that shows exactly how you’d use DRAG computation to compress a schedule. You might try that.
I hope I’ve helped, Tanveer. TPC is a pretty complicated subject. My book and articles have occupied many, many months of time in writing them. So try those sources and then you may be able to ask me some targeted questions.
Fraternally in project management,
Steve the Bajan
Email: PPadmin@planningplanet.com
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