Project Scheduling Crashing26042007

7/28/2019 Project Scheduling Crashing26042007

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Step By StepStep By Step

Crash ProjectCrash Project



2

Techniques for Shortening aTechniques for Shortening a

Project ScheduleProject Schedule Add people to the schedule. Add people to the schedule.

Work longer hoursWork longer hours (Over Time).(Over Time).

Improve productivity.Improve productivity.

Overlap tasks or make serial tasks simultaneous or Overlap tasks or make serial tasks simultaneous or

parallel activitiesparallel activities (Fast Track).(Fast Track).

Remove or delay features or functionality from theRemove or delay features or functionality from the

project critical pathproject critical path (Cut Scope)(Cut Scope)

Consider innovative approaches such as a differentConsider innovative approaches such as a different

development methodology / alternative technologies.development methodology / alternative technologies.

Out-sourcing options.Out-sourcing options.



3

Crashing PrioritiesCrashing Priorities

► Critical Path’s activities (Starting withCritical Path’s activities (Starting with

lowest crash cost / day)lowest crash cost / day)

► Near critical activities with lowest floatNear critical activities with lowest float(Slack).(Slack).

► In case of equals. Start with lowest activityIn case of equals. Start with lowest activity

ID numbers.ID numbers.



4

CAUTIONSCAUTIONS

► Shortening or lengthening tasks on the critical path directlyShortening or lengthening tasks on the critical path directlyaffects project finish time.affects project finish time.

► Duration of “non-critical” task is irrelevant.Duration of “non-critical” task is irrelevant.► ““Crashing” all jobs is ineffective, focus on the few % of Crashing” all jobs is ineffective, focus on the few % of

jobs that are on the Critical Path (s). jobs that are on the Critical Path (s).► ““Crashing” task can cause shifting the Critical Path to aCrashing” task can cause shifting the Critical Path to adifferent Paths (Tasks).different Paths (Tasks).

► Shortening task- technical and economical challenge.Shortening task- technical and economical challenge.► Previous non-critical task can become critical.Previous non-critical task can become critical.

► Lengthening of non-critical task can also shift the criticalLengthening of non-critical task can also shift the criticalpath.path.

► Project length should be reduced as long as crashing costsProject length should be reduced as long as crashing costsare less than indirect cost.are less than indirect cost.



5

Cost TypesCost TypesIndirect Cost Indirect Cost :: Costs related proportionally Costs related proportionally with the duration of the project - (Shared with the duration of the project - (Shared cost with other projects or company units) - Whencost with other projects or company units) - When activities areactivities arecrashed crashed these tend tothese tend to decrease the Indirect cost of The project:decrease the Indirect cost of The project:

Overheads : Admin. ExpensesOverheads : Admin. Expenses Office Rental Office Rental

SupervisionSupervision

ConsultantsConsultants Interest Interest

Direct Cost Direct Cost ::Costs related directly Costs related directly with the duration of the project - Whenwith the duration of the project - When activitiesactivitiesare crashed are crashed these tend tothese tend to increase the direct cost of The project.increase the direct cost of The project.

Labor Labor Equipment Equipment MaterialsMaterials Sub-contractorsSub-contractors



6

Time-Cost Trade-off Time-Cost Trade-off

Indirect cost - DecreasedIndirect cost - Decreased

C o s t ( $ )

C o s t ( $ )

CrashingCrashing

Direct cost - IncreasedDirect cost - Increased

Minimum Cost = Optimal Project Time / CostMinimum Cost = Optimal Project Time / Cost

Minimum Cost = Optimal Project Time / CostMinimum Cost = Optimal Project Time / Cost

TimeTime

TotalTotal

Project DurationProject Duration

Project DurationProject Duration

CostCost

Non - Linear Cost Non - Linear Cost

Distribution Distribution

Optimal Project TimeOptimal Project Time

Optimal Project costOptimal Project cost



7Cost ( X $100 )Cost ( X $100 )

2020

1818

1616

1414

1212

1010

88

66

44

22

5 10 15 20 25 30 35 40 455 10 15 20 25 30 35 40 45

Crash This Activity 4 Days FromCrash This Activity 4 Days From 2020 ToTo 1616

MarginalMarginal

CostCost

=

CC – NCCC – NC

NT – CTNT – CT

=

4000 –4000 –20002000

20 – 1220 – 12

$ 250 / Day$ 250 / Day=

CrashingCrashing

CT = 12 daysCT = 12 days

CC = $4000CC = $4000

NormalNormal

NT = 20 daysNT = 20 days

NC = $2000NC = $2000

Job time = 16 days Job time = 16 days

Total Cost = $3000Total Cost = $3000

ActivityActivity

DurationDuration

DaysDays

Time-Cost Time-Cost Trade-off Trade-off

Crashing Cost = 4 * $ 250 +Crashing Cost = 4 * $ 250 + $$ 2000 = $ 30002000 = $ 3000

N T

– C T

N T

– C T

CC – NCCC – NC

Linear Cost Distribution Linear Cost Distribution



8

Time-Cost Trade-off Time-Cost Trade-off ExampleExample

A $20 1

B $40 2

C $30 1

D $25 4

E $30 2

F $30 1

G $0 0

ACTIVITY

ID

CRASH

COST PER

DAY

MAXIMUM

CRASH

TIMETIME COST TIME COST

3 $50 2 $70

6 $80 4 $160

10 $60 9 $90

11 $50 7 $150

8 $100 6 $160

5 $40 4 $70

6 $70 6 $70

NORMAL

DIRECT COSTS

CRASH

INITIAL TOTAL DIRECT COSTS = $450INITIAL TOTAL DIRECT COSTS = $450INITIAL TOTAL INDIRECT COSTS = $400INITIAL TOTAL INDIRECT COSTS = $400

SAVING INDIRECT COST PER CRASHED DAY = $50/DAY.SAVING INDIRECT COST PER CRASHED DAY = $50/DAY.



9

Original NetworkOriginal Network

1 B E

A $20 6 8

B $40 A C G

C $303 10 6

D $25 D F

E $30 11 5

F $30

CRASHING COST = $0CRASHING COST = $0

INITIAL TOTAL DIRECT COSTS = $450INITIAL TOTAL DIRECT COSTS = $450

INITIAL TOTAL INDIRECT COSTS = $400INITIAL TOTAL INDIRECT COSTS = $400

INITIAL TOTAL COSTS = $450 + $400 = $850INITIAL TOTAL COSTS = $450 + $400 = $850

PROJECT DURATION = 25 DAYS.PROJECT DURATION = 25 DAYS.

A-B-E-G = 23 DAYS

A-C-F-G = 24 DAYS

A-D-F-G = 25 DAYS



10

2 B E

A $20 6 8

B $40 A C G

C $30 2 X 10 6

D $25 D F

E $30 11 5

F $30

TOTAL CRASHING COST = $20TOTAL CRASHING COST = $20

INITIAL TOTAL DIRECT COSTS = $450 + $20 = $470INITIAL TOTAL DIRECT COSTS = $450 + $20 = $470

INITIAL TOTAL INDIRECT COSTS = $400 - $50 = $350INITIAL TOTAL INDIRECT COSTS = $400 - $50 = $350



Crash “ A ”Crash “ A ”

$20$20

A-B-E-G = 22 DAYS

A-C-F-G = 23 DAYS

A-D-F-G = 24 DAYS



11

Crash “ D ”Crash “ D ”

3 B E

A $20 6 8

B $40 A C G

C $30 2 X 10 6

D $25 D F

E $30 10 5

F $30

TOTAL CRASHING COST = $20 + $25 = $45TOTAL CRASHING COST = $20 + $25 = $45





$20$20

$25$25

A-B-E-G = 22 DAYS

A-C-F-G = 23 DAYS

A-D-F-G = 23 DAYS



12

Crash “ F ”Crash “ F ”

4 B E

A $20 6 8

B $40 A C G

C $30 2 X 10 6

D $25 D F

E $30 10 4X

F $30

TOTAL CRASHING COST = $20 + $25 + $30 = $75TOTAL CRASHING COST = $20 + $25 + $30 = $75





$20$20

$25$25 $30$30

A-B-E-G = 22 DAYS

A-C-F-G = 22 DAYS

A-D-F-G = 22 DAYS



13

5 B E

A $20 6 7

B $40 A C G

C $30 2 X 9X 6

D $25 D F

E $30 9 4X

F $30

TOTAL CRASHING COST = $20 + $25 + $30 + $25+ $30 + $30 = $160TOTAL CRASHING COST = $20 + $25 + $30 + $25+ $30 + $30 = $160





$20$20

$25$25 $30$30

Crash “ D,C and E ”Crash “ D,C and E ”

$25$25

$30$30

$30$30

A-B-E-G = 21 DAYS

A-C-F-G = 21 DAYS

A-D-F-G = 21 DAYS



14

Time-Cost Trade-off Time-Cost Trade-off

Crash ResultCrash Result

PROJECT DURATIONTOTAL DIRECT COS TOTAL INDIRECT COS TOTAL PROJECT COSTCRASHING COST

25 450 400 850 0

24 470 350 820 20

23 495 300 795 45

22 525 250 775 75

21 610 200 810 160

CRASH PROJECT

$ 8 5 0

$ 8 2 0

$ 7 9 5

$ 7 7 5

$ 8 1 0

0

100

200

300

400

500

600

700

800

900

25 24 23 22 21

PROJECT DURATION

C O

S

TOTAL

PROJECT

COST

TOTAL

DIRECT

COST

TOTALINDIRECT

COST

CRASHING

COST

OPTIMUMOPTIMUM

COST – TIME POINTCOST – TIME POINT

OPTIMUMOPTIMUM

PROJECT DURATIONPROJECT DURATION

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Project Scheduling Crashing26042007