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Updated on February 7, 2012

No project is implemented in isolation. Events happening around the project may affect its progress. A nation-wide strike, an un-expected calamity or an abrupt economic change may bring the project to a grinding halt. Even if everything goes well, the sponsors may be tempted to enter the market early. In all cases, the project  manager plays a vital role in shortening the project schedule. To start with, a manager should study fast-tracking or shift to an advanced technology. If nothing helps, more resources can be introduced for an early completion. Since it would invariably result in more costs, a manager must find out if, within the same time-frame, the costs could be brought lower than the crash-cost limit. This has been explained by Crashing Techniques through an example of a Yacht Project.


In crashing, the time is reduced by increasing resources. But the sequence is not disturbed. For example, a project involves raising a boundary wall in 16 days and moving machinery crates in 8 days, the total duration being 24 days. By engaging more workers and excavators, the boundary wall can be made in 12 days and machinery shifted in 4 days, reducing total time to 16 days.

Eating & driving
Eating & driving

In fast tracking, shifting of machinery would start when boundary is only partially complete, usually 2/3, and the entire job would be completed in 16 days without incurring extra cost. But it would increase risk to a certain degree. It is like drinking coffee or using mobile phone while driving in a fast lane.

To sum up, crashing involve time and cost trade off without any change in sequence of activities or task-dependencies. On the other hand, fast tracking does not increase costs but increases the risk as many jobs are done in parallel rather sequentially. 


In theory, crashing is done by throwing in additional resources but using the same techniques as in normal conditions. It is not a switch over to an advanced technology to complete a job in a very short time as shown below:

  • In Sri Lanka, a flyover was completed in just 60 days setting a world record. Instead of bringing sand, cement and steel to the site, pre-fabricated pillars and beams were moved in, lifted by cranes and bolted together.
  • In Scandinavian countries, helicopters are being extensively used for transporting large items like furniture, building materials, pipes, tiles and boards.
  • By using Micro-ovens, food can be cooked in a matter of minutes.
  • Angioplasty has displaced bypass surgery. Angioplasty requires a mere slit and one-night stay as opposed to Open Heart Surgery taking 5-7 days in hospital and six weeks of recovery.

A simple example

Two Scenarios

In order to help the manager, two types of networks are prepared. One represents normal conditions and the other crash conditions. Time and costs are calculated for each activity under both scenarios.

The activity 'A', shown in the side-table, can normally be completed within 5 days at a total cost of Rs.5,000. It may be possible to reduce the time to three days by (i) putting in more resources, (ii) allowing overtime-premium and / or (iii) introducing incentives to increase productivity.

Three consideration in time reduction

If we want to reduce the duration, we would have to consider three aspects:

(1) Time can only be reduced if we reduce duration of any activity on the critical path. For example, if we reduce A by 2 days, the total time would be reduced to 15 days. But if we reduce B by 2 days, total time would still remain the same I.e. 17 days.

(2) In this example, both A&C can be crashed as both are on the Critical Path. We should crash that activity which is cheaper. Incremental Cost for crashing A is Rs.1,250 (difference in Costs divided by difference in Time). The same cost in case of C would be Rs.500 per day. Obviously, we would prefer to reduce C by permissible time of 8 days.

(3) After crashing any activity, we would re-draw the network and re-assess the situation.

There are many paths in a network.  When we crash activities on the Critical Path, another path may become critical as will be observed later in this hub. 



As stated above, we can crash C by 8 days for which would have to incur an extra Rs.4,000 (8 days @ Rs.500 per day). After the crash, we re-draw the network.


A glance at the revised network would reveal that total time under the path A- C has reduced to 9 but B, on the other path, has time duration of 12 days. As critical path is the longest path, total time duration has only reduced to 12. Since our crash time is 10 days, we would now reduce B by two days.


For technological reasons, it is not possible to shorten the duration below the crash limit of 10 days even by spending more money or resources. But we can review the situation and reduce the crash cost to some extent. This is done through un-crashing.

After second crash, we observed that path A&C had a duration of 9 days. If we can increase any activity by one day, we would still be under the permissible limt of 10 days. As a rule, an activity with the highest per-day cost should be un-crashed. In this case, however, only C can be uncrashed for one day as the other A has never been crashed.

By doing so, we would make all paths as critical paths. Total cost would now be Rs.39,100 as under.


In the previous example, only three activities were used which resulted in two paths. Life is not as simple as that. In next example, 8 activities are introduced which brings in five paths. This would be a little difficult to solve. At the same time, some readers may find it interesting how a yacht can bring thrills and pleasure.

A simple example of Time & Cost under two scenarios

In turning the above statement into a network, we would draw a box for 'A' since it is a start activity. Once this is done, both B&C can be shown side by side. We would keep on adding the remaining activities keeping in mind their precedents as shown in the following sketch.

Yatch Project - Network under Normal Conditions

Once we have draw the network, we can insert durations of each activities. It would be noted that in normal circumstances, the project completion stands at 28 days. If we swtich normal durations with crash durations in the same network, the time-frame would get reduced to 18 days.

Going back to normal network, we observe that there are five paths of varying duration. Critical Path is the longest path which is A-B-D-G with 28 days duration. Naturally, if we reduce any activity in this path, our project time would be reduced. Of A,B,D & G, the cheapest is D with per day cost of Rs.80,000. We can crash it by two days.

The CPM has now shifted to A-C-E-G with 27 days duration. Among them G is the cheapest and can be crashed for 3 days. Since G is included in another path (A-B-E-G), we reduce 3 days from both the paths. Similarly, we would crash C,B & A. We can go on till we reach the crash time, 18 days in this case.

Finally, we can uncrash some activities provided that: (i) the same are not on the critical path, and (ii) have been crashed before. The activity to be uncrashed would be the one with highest per day cost. In our case, we find only C meeting that criterion and add back crash cost for two days. Hence, our final crash cost would be Rs.10,916(,000) as against original crash cost of Rs.11,240(,000), showing a saving of Rs.324,000.

This is explained by a short statement:



Sometimes we are faced with conflicting situation like two critical paths or two activities in the same path with the same crashing costs per period. The priority rules are:

  • If there is more than one critical path, crash one which contains cheapest activity.
  • In case, a path contains two activities with the same crashing cost per day, crash one with the high reduction time.
  • In case, reduction time is also the same, crash one with higher ID.

For example, if there are two activities,C&E, and both are in the same path, have the same daily crashing costs, have the same reduction time, we would crash E as it has a higher ID.


Apart from Activity Costs, there are Indirect Costs like Managerial Services, Site Office Maintenance and Consultants Fees to be paid on daily or weekly basis. Unlike direct costs, the indirect costs would decrease with the reduction in time. In other words, indirect costs have a perfect positive correlation with the time period as against negative correlation of the activity cost. Because of this, their slopes differ as shown below:

Direct, Indirect & Total Cost behavior


Crashing may be taken as a war against time. It may fire back. Inducting new workers may result in classic conflict between old and new. Moreover, the new workers may not be well oriented with job and the environment. In a worst scenario, this may lengthen the project schedule instead of reducing it.

As a thumb rule, more you crash, more you spend. In some cases, this would not pass the traditional cost & benefit test. Unless there are clear-cut advantages, a manager should not resort to crashing as some important aspects may be ignored in a haste.


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    • profile image

      gepeTooRs 2 years ago

      Virtually no tool matches the simplicity of which No Hands SEARCH ENGINE OPTIMIZATION has, the one required plugs are your blog street address, search keyword phrases and desired single point texts and also NHSEO will do devices available for you.

    • profile image

      phineas 3 years ago


    • profile image

      neneth 4 years ago

      thank you

    • hafeezrm profile image

      hafeezrm 5 years ago from Pakistan

      Please ask a specific question;

    • profile image

      londiwe 5 years ago

      still clueless

    • hafeezrm profile image

      hafeezrm 5 years ago from Pakistan

      Thank for the question. You said the project has been delayed. In this case there should be a time indicator like SPI not CPI.

      Further you say that time is extremely important like (i) there may be penalty for delay, (ii) there may be a loss of revenue or market. These incidences can be quantified which would give an idea of benefit for timely completion.

      If you can complete the project on urgent basis by incurring lesser amount, this would pass the cost-benefit test. So other things (like risk in crashing, problem in disruption of original schedule) remaining the same, one can go for crashing.

      Please note that loss reduction is a benefit which may include other intangible consequences like reputation for timely completion, pride of performance, employee morale)

    • profile image

      surianarayanan 5 years ago

      Good Morning sir,

      CPI(Cost performance indicator), if its bellow 1 than i guest it means that the actual cost has exceeded the budgeted cost.Since we have delayed and time is extremely important, I guest i should crash the project to minimize other losses. Can you comment again.

    • hafeezrm profile image

      hafeezrm 5 years ago from Pakistan

      Crashing is a trade off between time and cost. It is beneficial in case of (i) an urgency for completion of the project to gain the market access. (ii) considerable time has been lost and speedy implementation is required for completion in time, (iii) resources are needed elsewhere.

    • profile image

      Fahmida Islam 5 years ago

      Dear Sir,

      What is the importance of Crashing? just give me some points. Please

    • hafeezrm profile image

      hafeezrm 5 years ago from Pakistan

      CPI ? You mean Slope.

      What is good or bad in crashing depends on Cost-Benefit Analysis or Risk and Return Reward. Crashing increases costs and must be compensated by more benefits. If none, why crash. (Slope sets relative importance, a single slope figure does not mean anything.

    • profile image

      surianarayanan 5 years ago

      Dear sir,

      Let say if the CPI is 0.88, will it be good to use crashing method.

    • profile image

      Curt 6 years ago


    • hafeezrm profile image

      hafeezrm 6 years ago from Pakistan

      @Tharun Thomas

      In the question, both normal time and crash time are given. Crash time is a technical bottleneck, one cannot do work in the less than that by just adding the resources. (Change in technology is not part of crashing).

      So you would draw two networks: Normal and Crash. The critical path of the crash network would set your limit. There may be some individual activity which can be crashed further but it would not be on the critical path and so crashing it would serve no purpose.

    • profile image

      Tharun thomas 6 years ago

      Sir i still have a doubt.

      How can we fix the no of days to be crashed for an activity ?

    • hafeezrm profile image

      hafeezrm 6 years ago from Pakistan

      @curt. It is a mistake. When uncrashing, the cost should be reduced. It should have been 10,404. Thanks for observing.

    • profile image

      curt 6 years ago

      In the first question's solution you have subtracted 500 which is the cost of uncrashing but in the solution of second question u have added the cost of uncrashing. Why

    • profile image

      zohaibnoor 6 years ago

      thanks to share this sir .

    • hafeezrm profile image

      hafeezrm 6 years ago from Pakistan

      Thanks Muhammad Adil Khan for your comments.

    • profile image

      Muhammad adil khan 6 years ago

      Dear sir,

      That is great learning, I m feeling much easier now, it would help me understand CRASHING effectively. Thanks a lot for your devotion in writing HUBs, It simply is an efficient learning with no Cost.


    • hafeezrm profile image

      hafeezrm 6 years ago from Pakistan

      The question would have to be reconstructed in order to understand. It would be better if you send it to me by email attached the question in its original format like a table having proper headings. My email is

    • profile image

      Margaret Bennett 6 years ago

      Hi - this is not a comment but a queston. Is there anyy person that can help me with a solution for the question below about crashing?

      The following graph is about a CPS model for lowest-cost project schedule representing time-cost trade-off (i) for each individual activity of a project and (ii) for a project as a whole. This involves direct costs associated with individual project activities (which increase if activities are expedited/crashed) and indirect costs of N$6.50 associated with the project as a whole. (Which decrease if the project duration is shortened or increase if the project duration is extended.

      A b

      5 – 3 6 - 4

      (6) (8) d

      C 7 - 3

      9 – 5 (4)


      a. Find the lowest-cost schedule for completing the project (20 marks)

      b. Present the various schedule lengths( in sequential steps you followed to reach the lowest-cost schedule) in a project cost-time curve and shoe the lowest cost point

    • hafeezrm profile image

      hafeezrm 6 years ago from Pakistan

      Thanks Muhammad Adil Khan for your comments.

    • profile image

      Muhammad Adil khan 6 years ago


      Respected Sir, Thank you so much for sharing this article.

      This article gives the clear cut concepts of crashing and especially the difference between crashing and fast tracking is of vital importance.


    • hafeezrm profile image

      hafeezrm 6 years ago from Pakistan

      In crashing time, you just add more resources like labor and equipment. The mode or technology is NOT changed such as use of helicopter to transport material rather 4 trucks instead of two.

    • profile image

      Umesh 6 years ago

      Dear Sir,

      Great article, thank you very much.

      I'm new to the subject so appreciate very much if you could list out common crashing techniques (Which could be used in any project).



    • hafeezrm profile image

      hafeezrm 6 years ago from Pakistan

      You are welcome Trevorita.

    • profile image

      TREVORITO 6 years ago


    • hafeezrm profile image

      hafeezrm 6 years ago from Pakistan

      Thanks Tapera for your comments.

    • profile image

      Tapera 6 years ago

      Great, you have made my day! Stay blessed!

    • hafeezrm profile image

      hafeezrm 6 years ago from Pakistan

      ID means identity. It simplifies the process. A, B, C & D are all ID representing various activities. It is easy to say "Crash B" which is the same as "reducing duration of activity - Construction of Deck."

    • Naim Hasan profile image

      Naim H 6 years ago from Dhaka

      and i have a supplement question to ask, what does ID mean? Thanks in advance.

    • Naim Hasan profile image

      Naim H 6 years ago from Dhaka

      Thanks mr. hafeez for a detailed explanation on crashing.

    • hafeezrm profile image

      hafeezrm 7 years ago from Pakistan

      Dear Shoaib,

      Each activity has ID like A & T. If these are in equal, activity with higher ID could be crashed which in this case would be T.

    • profile image

      M TAHSEIN JAWED 7 years ago


    • profile image

      Muhammad Shoaib Ikram 7 years ago

      Sir, under the heading of 'When a Conflict Arises', it could not understand the meaning of the term 'ID'.

    • asadayub profile image

      asadayub 7 years ago

      Respected Sir, Thank you so much for sharing this article. This is of-course one of the difficult topics to cover, but i'm now pretty much strong on the concepts about which activity to crash, and which to un-crash. The rules are also very well explained as to which activity should be crashed first. Thank You so much sir for such a nice hub.

    • profile image

      kamranqamar 7 years ago

      sir, excellent article. immaculately explained.bravo..thnx

    • profile image

      Amna Jamal 7 years ago

      Thank you sir for posting this article.

      It helped me a lot .

    • profile image

      Dr.Yusuf Al-Malki 7 years ago

      That was a great works, Many thanks to you.

    • profile image

      Sikujua Seboru 7 years ago

      God bless you for the great wisdom,

      this was extremely helpful to me.

      get me on

    • profile image

      hira sami 8 years ago

      very well expalined



    • hafeezrm profile image

      hafeezrm 8 years ago from Pakistan

      Sadaf Saleem:

      There are eight activities: A,B,C,D,E,F,G & H

      Of these: A,B,D & G are already on the critical path while E,F & H were never crashed. This leaves C which is in the two paths i.e. A-C-E-G and A-C-F-H. At best we can uncrash C by two days.

      Hope this is clear to you.

    • profile image

      Sadaf Saleem 8 years ago

      Thank you so much for providing us such a wonderful info....Specially the case study examples and numericals are really helpul and reflects your deligence...

      Sir, I have solved the complex examole but my answer to uncrashing is 3 days...ive tried saveral times...can u plz help me??

    • profile image

      sanhita das 8 years ago

      it is a useful article

    • asif jamal profile image

      ASIF JAMAL 8 years ago from Islamabad

      thnks sir

      this is morehelpful to undersatnd the subject(PM)

    • profile image

      maria 8 years ago

      thanx alot sir for increasing our knowledge!

    • SHAHZAD,AHMED profile image

      SHAHZAD,AHMED 8 years ago

      Respected Sir,

      This article gives the clear cut concepts of crashing and especially the difference between crashing and fast tracking is of vital importance. Further the examples are simple and easy to understand. Sir, your given material in this article is really authentic and easily understandable.

    • Rufi Shahzada profile image

      Rufi Shahzada 8 years ago from Karachi

      Dear Sir,

      That is great learning.... I m feeling much easier now, it would help me understand CRASHING effectively. Thanks a lot for your devotion in writing HUBs, It simply is an efficient learning with no Cost!




    • profile image

      Zakira Perveen 9 years ago

      Superb...lovely...marvellous post. You rock!

    • profile image

      samreen habib 9 years ago

      Assalam-o-Alaykum sir,

      Now i can understand at which time we should start crashing & till what time we should continue ....thanks

    • Fahad_Khan profile image

      Fahad_Khan 9 years ago from Karachi

      Thanks a lot to Mr. Hafeez for taking out time and writing this article in the most elaborate manner. It has cleared all my confusions and strengthened the concepts regarding the topic.

    • profile image

      ASAD SHERAZ 9 years ago

      After reading of this articale i completely understand the crashing thank you.

    • profile image

      Sher Attiq-ur-Rehman 9 years ago

      Thank again:

      when i read the crashing article so,then i fully understand and Thank agains the sharing the crasing and uncrasing information.

    • Emran Ali profile image

      Emran Ali 9 years ago from karachi

      Dear Mr Hafeez

      It is one of the toughest topic in Project management , Your this article has certainly makes it easy to understand about crashing and un-crashing in both ways statement wise and network wise . Thank so you much for sharing such an important article which gaves me deep knowledge and certainly limpid ambiguity in certain areas .

      Best Regards

    • hafeezrm profile image

      hafeezrm 9 years ago from Pakistan

      Dear Bilal Zafar,

      When you have crashed all activities, you may find that there were some activities which were un-necessarily crashed. Such activities are on non-critical paths. If your critical path, under crash condition, was of 10 days and you observed that another path had only 8 days, you will be tempted to increase the same to 10 days. But for this, you have to find out that such activities have already been crashed. Once you are sure of this, you may go through their crashing cost per day. It would make sense that you uncrash that activity which has the maximum crash cost (as against minimum for crashing. Remember in crashing you spend but in un-crash you recover).

      In Yacht examples, the critical path consists of A-B-D-G while there are four other paths which contain C,E,F & H. Of these, E, F & H have never been crashed. So it leaves only C which can be uncrashed by two days to make it 10 (8+2).

    • profile image

      Bilal Zafar 9 years ago

      Dear Mr Rehman

      You were kind to post this article to increase our knowledge and strengthen our concepts about crashing.

      You are requested to provide some elaboration on the uncrashing phase of the process as my concepts are still vague about it. I am confused about which activity to uncrash and by how many days.


    • profile image

      MUHAMMAD DANIAL 9 years ago




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