audio


 

 



Crashing

by chrisfoya

Crashing is a process of expediting project schedule by compressing the total project duration. It is helpful when managers want to avoid incoming bad weather season. However, the downside is that more resources are needed to speed-up a part of a project, even if resources may be withdrawn from one facet of the project and used to speed-up the section that is lagging behind. Moreover, that may also depend on what slack is available in a non-critical activity, thus resources can be reassigned to critical project activity. Hence, utmost care should be taken to make sure that appropriate activities are being crashed and that diverted resources are not causing needless risk and project scope integrity.

Indeed, it is advisable to first crash activities early in the project as to have a leeway to crash other activities in the later stages of the project. Nonetheless, it is imperative that all project guidelines, resources and costs are diligently being tracked and are aligned to the aspirations of the client and senior managers.

[Editor Note: Please see this video I recorded on project crashing too. For coaching from me, check out Project Management Strategies That Work (And How To Implement Them)]

Leave a Comment

{ 15 comments… read them below or add one }

Bill Duncan November 17, 2008 at 12:19 pm

Well … the definition isn’t quite right even if most of the advice is. From Max Wideman’s glossary:
– Action to decrease the duration of an activity or project by increasing the expenditure of resources.
– Taking action to decrease the total project duration by analyzing a number of alternatives to determine how to get the maximum duration compression for the least cost.

The first definition is Max’s preferred definition, but I find it lacking because it (a) ignores the idea of optimization or consideration of alternatives, and (b) implies that one might crash an activity even if doing so provides no benefit.

The second definition is from Earl Glenwright and was used in the 1996 PMBOK Guide.

Duncan

Reply

Dr. Paul D. Giammalvo November 18, 2008 at 12:24 am

Yes, I agree with Bill, but would like to elaborate a bit. There are two rules which apply to crashing: 1) Crash ONLY activities which are on the critical path and; 2) Prioritize which activities on the critical path to crash based on which ones provide the most schedule compression at the least possible cost. (per Bill’s comment on optimization)

Also keep in mind that there is another “schedule compression” technique, which is “fast tracking”. Fast tracking offers the advantage of NOT necessarily increasing costs, but does require the availability of more resources and/or is constrained by the law of diminishing returns. Fast tracking is also constrained by safety and quality considerations. (to many people working together in close proximity can cause safety hazards as well as cause damage to each others work)

BR,
Dr. PDG, Jakarta

Reply

maaz April 14, 2013 at 5:45 am

Respected sir,
what’s the condition/criteria for crashing activity duration ? please emphasize on this part of crashing(activity duration) . I found a following formula on internet [min{normal duration-crash duration , float limit}]..note: float limit is not equal to float..please help.

Reply

admin April 16, 2013 at 10:36 am

Hi Maaz,
Are you looking for a formula or the reason why you would do it or?
The formula I use is Slope = (Crash Cost – Normal Cost)/(Normal Time – Crash Time)

The slope is how much it costs to crash an activity. Of course the activities you care about are the critical path activities, but as you change your schedule, you might change the critical path.

The point where your total costs are the lowest is the point where it makes financial sense to crash.

Reasons to crash (or not)
Pros: Identifies what critical path tasks can be compressed and
how much it costs to do so.
Cons: Your new estimates could be wrong and you may not
compress the schedule.
Best Application:
If you want to try to compress the schedule this approach will show
you the point at which your payback is the greatest.

Reply

Chris Foya April 16, 2013 at 9:12 pm

the cost to crash per period assumes
that the relationship between adding
more money to the activity and
reducing the time is linear. Spend half
of the money, and get half the time
reduction, spend more of the money and
get more time reduction. This is not always
true in practice, but works alright for a
rough planning technique. If faced with incoming
bad weather reason will dictate that more resources
must to be spent to save time meet project dead-line.
This action could avoid unforeseen future cost overruns.

Reply

admin April 18, 2013 at 12:26 pm

Chris,
You are correct the crashing formula is linear and life is not!
Margaret

Reply

maaz April 20, 2013 at 6:34 am

Sir i want to know that is there any limit of crashing an activity duration..(i know we cant crash it down beyond the given crash time)..for better understanding of my question let me use an example.
for example..
for activity “A”
normal time=5 and crash time=2…and if “A” is a critical activity with least cost slope…and i must crash it…then should i crash the activity duration of “A” to the minimum (i.e.; 2 in our case).or does some factors are to be checked and then i may be able to crash it down by only 1 or 2 units(depending upon the factors).
hope you understood my question..

Reply

admin April 23, 2013 at 11:33 am

Maaz,
I see. Just because YOU CAN crash A from 5 days to 2 days does not mean you SHOULD. You definitely want to take a look at the increased risks and the probablity of those risks occuring and the impact they will have. For example if your team member tells you that he can crash A to 2 days but there is only a 40% chance that he will be successful, would you still do it? If he told you that he felt 70% confident with crashing it to 3 days, perhaps that would be a better choice.
It is about tradeoffs and constraints. You might also consider the fact that if you need to reduce the schedule by 3 days – it might be less risky to remove those 3 days from more than ONE critical path activity – UNLESS you do have one critical path activity that is many days in duration. But in this example where A is 5 days and we can crash it to 2 days, if we are unsuccessful we might be out of luck. But if we crash A for one day and B for one day etc…. although we have more tasks that need to meet the new date, we have not placed all of our plan on one activity.
Crashing is definitely more than the mathematical equations, it involves strategy and analysis and good risk planning too!
Thank you,
Margaret

Reply

maaz April 23, 2013 at 12:42 pm

thank you admin..:)

Reply

Chris Foya April 16, 2013 at 9:25 pm

In my case a refresher course will do no harm for I still need to be certified. I already took a major training at Kaplan University.

Reply

admin April 18, 2013 at 12:25 pm

Sometimes crashing is not discussed in detail or sometimes not at all. So if you did not see it in your courses before, it is not you.

Reply

Olga April 19, 2013 at 9:03 pm

How would you crash activity when cost of activity is unknown and the cost of crashing is unknown. Only known late penalty? There is slack of 14 days is available from none critical path. The activity that needs to be crashed previously were duration of 12 days, but because of a strike at the subcontractor responsible for the activity company for this activity it became 55 days duration. What would you do in this case? Thank you.

Reply

admin April 23, 2013 at 11:38 am

Olga,
With a task which has grown to 55 days in duration – my 14 days of float are gone. So it no longer matters if I could have used some of the float by redirecting resources to work on the critical path. You are already definitely late and as you note incurring a late penalty. In this instance I recommend a review and replan of the remaining work to be completed. The schedule needs to be reconfirmed as-is, THEN you can look at the critical path as it exists now and determine if resources can be moved from non-critical path tasks to critical path tasks. You might also consider working extra shifts and you might consider fast-tracking or executing more tasks in parallel when it makes sense to do so. Not knowing the costs of these actions is limiting. What you can determine is how much you are incurring for late penalties versus how much you would pay for the team to work extra shifts or to complete more work in parallel. It seems that now you are looking for cost avoidance.
Hang in there,
Margaret

Reply

Olga May 14, 2013 at 12:05 am

Margaret, Thank you so much for your advise! Do you think taking into consideration the length of the original critical path is a good idea?

The new critical path now is 79 days, which is 42 days longer than original critical path (37).
First I would analyze all the activities on the non critical paths and use the slack times from the activity G -14 days and Activity D – 5 days relocating the resources from this activities (G and D) to the activity B (now 55 days). Relocating the resources to the activity B will shorten the activity B by 19 days, therefore reducing the critical path from 79 to 60 days.
Keeping in mind that the original critical path is 37 days, I would need to reduce a new critical path by only 23 days.
I would crash the critical path by 23 days, finding the lowest cost crash activity first. Crashing activities would include using the additional funds to support additional personal, adding more efficient equipment, working extra shifts. As well I could consider fast-tracking of precedes activities.
I would continue crashing the activity on the critical path until the incurring cost is less than the incurring penalty.

Pleas let me know what do you think about my approach?

Thank you!

Reply

online reputation April 30, 2013 at 10:08 pm

I’ve been surfing on-line more than three hours today, but I never found any interesting article like yours. It’s pretty worth enough for me.

Personally, if all website owners and bloggers made
just right content as you probably did, the web will likely be much more useful than ever
before.

Reply

Previous post:

Next post:

audio