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Allocating Resources to the Project

Expediting a ProjectFast-Tracking a ProjectResource LoadingAllocating Scare Resources

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Introduction• Projects Compete With One

Another for Resources– resources that are not consumed– resources that are consumed

• Goal of Resource Allocation is to Optimise Use of Limited Supply

• Requires making trade-offs– time constrained– resource constrained

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EXPEDITING A PROJECT

• The Critical Path Method• Probabilistic Activity Durations• Fast-Tracking a Project

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The Critical Path Method

• Normal Duration Estimates

• Normal Costs• Crash Duration Estimates• Crash Costs• Crash Cost Per Day

Cost Normal -Cost Crash DurationCrash -Duration Normal

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Probabilistic Activity Durations

• Three time estimates made for both normal resource loading and crash resource loading

• Variance of normal activity may be different than variance of crash time

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Fast-Tracking a Project• Used Primarily in

Construction Industry• Building phase started

before design and planning phases completed (Scottish Parliament)

• Particularly appropriate when large proportion of work is routine

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Resource Loading

• Amount of specific resources that are scheduled for use on specific activities or projects at specific times.

• Usually a list or table.

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Use of Software• Begin with Pert/CPM

Schedule• Activities examined

period by period and resource by resource

• In cases where demand for resource exceeds supply, tasks considered one by one and resources assigned to these tasks based on priority rules

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Some Priority Rules• As soon as possible• As late as possible• Shortest task duration

first• Minimum slack first• Most critical followers• Most successor• Most resources first

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Resource Loading/Leveling and Uncertainty

• What about– Workers getting sick?– Task not ready when

worker is ready?– Change orders?

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Pseudo activities• Used to link several project

together• Have duration but do not

require any resources• This approach allows a set

of projects to be dealt with as though it were a single project– use of MSP’s resource

loading and leveling charts and tables

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Bottle Necks• Identify the constraint • Exploit the constraint• Subordinate everything

else• Elevate the constraint• Go back to step 1

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Goldratt’s Critical ChainWhat is it?

• Tackles the inherent uncertainty in managing projects

• Systems approach

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Goldratt’s Critical Chain• Similar issues that trouble people

about working on projects regardless of type of project– unrealistic due dates– too many changes– resources and data not available– unrealistic budget

• These issues/problems related to need to make trade-offs

• To what extent are these problems caused by human decisions and practices?

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Observations

• Average Completion Times

• Implications of Assuming Known Activity Times

• Worker Time Estimates• Impact of Inflated Time

Estimates• Student Syndrome

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Common Chain of Events

• Underestimate time needed to complete project

• Project team members inflate time estimates

• Work fills available time• Safety time misused• Misused safety time results in

missed deadlines

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Common Chain of Events concluded• Poor multitasking increases

task durations• Uneven demand on

resources also results due to poor multitasking

• More projects undertaken to ensure all resources fully utilized

• More projects further increases poor multi tasking

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Reversing the Cycle• Reduce number of projects

assigned to each individual• Schedule start of new

projects based on availability of bottleneck resources

• Reduce amount of safety time added to individual tasks and then add some fraction back as project buffer– activity durations set so that

there is a high probability the task will not be finished on time

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The Critical Chain• Longest chain of

consecutively dependent events– considers both precedence

relationships and resource dependencies

• Project Buffer• Feeding Buffer

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Critical Chain Rules1. Projects should not be

started ASAP2. Tasks and resources

should not be precisely scheduled during planning

3. Adding explicit buffers into projects makes them run faster

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Buffer ManagementTaking the appropriate actionNo action needs to be taken, consumption of the buffer is expected

Identify the tasks consuming thebuffer, develop a recovery plan

Implement recovery plan Use information on task performancefor future improvement activities

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Why not start projects ASAP?

All three projects started ASAP• Constant resource shuffling• Priorities not synchronised• All projects are delayed

Start dates are staggered• Resources stay focused• Tighter synchronisation• All projects finish faster• More projects can be done

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Why not schedule precisely?Schedules set in planning• Uncertainties are unavoidable• Wanting to be reliable, people add safeties into estimates• Safeties get wasted in execution

Schedules set in Execution• Estimates are used only to plan projects• Task schedules determined in execution, when tasks are closer to being started

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How safety or contingency time is wasted

• Task dependency– Gains are wasted and delays are

passed on• Student Syndrome / Cherry Picking– Starting work is delayed• Parkinson’s Law– “Work expands to fill the time available”• Multi Tasking– A resource has to divide its time

between two or more tasks

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Benefits

• PROJECTS:• coming in on-time• completing within budget• completing without cutting• scope• reduced project lead-times• Improved efficiency

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Looking at the example of Breakfast in Bed there can be seen anumber of different tasks to perform, all of which have a resourceimplication.

Activity Effort(person-minutes)

Duration(minutes)

Butter toast 1 1Pour orange juice 1 1Boil egg 0 4Slice bread 1 1Fill pan with water 1 1Bring water to boil 0 3Toast bread 0 2Take loaded tray to bedroom 1 1Fetch tray, plates, cutlery 1 1Time resource estimates for "Breakfast in Bed" project

A resource allocation example

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Often estimates of the time taken are quite inaccurate

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Plan with Resource Allocation

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Revised Plan with Resource Allocation

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Plan with Levelled Resources and Warm Toast