IDENTIFYING THE CRITICAL PATH
1. Prepare the site Survey site
1.2. Plan alterations
1.3. Estimate building work 1.4. Contract builders
1.5. Purchase building materials 1.6. Carry out building work
1.1. About 3 weeks (needs discussions and an expert) 1.2. Only 1 week once we have the
information
1.3. 1 week because we’ll need to call builders in
1.4. 2 weeks because we need three estimates and decision
1.5. 1 week because builders will normally do most of this 1.6. About 4 weeks to knock down
walls and partition 2. Furnish and equip office
2.1. Plan furnishing needs 2.2. Identify what we have 2.3. Purchase furniture 2.4. Plan equipment needs 2.5. Identify what we have 2.6. Purchase equipment 2.7. Install equipment 2.8. Install furniture
2.1. 2 weeks because it needs discussion with staff
2.2. 2 weeks – could be done in same discussions
2.3. This normally takes 3 weeks to deliver
2.4. 2 weeks – similar discussions with staff needed
2.5. Same 2 weeks 2.6. Allow 3 weeks 2.7. 1 week
2.8. 1 week 3. Service preparation
3.1. Plan service during the move 3.2. Inform service users
3.3. Arrange resources needed 3.4. Deliver service during move 3.5. Prepare new staff locations and
rotas
3.6. Prepare info about new location 3.7. Inform when move completed
3.1. 2 weeks, needs discussion to share space
3.2. 2 weeks, need to discuss who and tell them
3.3. 2 weeks, might do this in same discussions
3.4. 1 week duration of move
3.5. 4 weeks, could be tricky and a lot to arrange
3.6. 3 weeks because we’ll need to print new stationery
3.7. 1 week as this can all be done by email and letter
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As some of these activities had a lot of separate tasks, the project manager checked each of these estimates against the task list to ensure that everything had been considered.
Once the times have been estimated for each activity it is possible to draw up a detailed schedule. You will probably have made a Gantt chart by this time and you may like to revise it in the light of the information that is now available. The revised Gantt chart may give enough information for you to go ahead without any further scheduling if timing in the project is not a par- ticular concern.
2.1 (any 2 weeks) 2.2 (any 2 weeks) 2.4 (any 2 weeks) 2.5 (any 2 weeks)
3.1 (any 2 weeks) 3.2 (any 2 weeks) 3.3 (any 2 weeks)
3.5 3.6
1.1
1 2 3 4 5 6 7 8 9 10 11 12 13 14
1.2 1.3 1.4 1.5 1.6
2.3 + 2.6 2.7
2.8
3.7 3.4
Figure 8.2 Critical path for relocation of an office
If the timescale is important there is a technique that can help you to be much more precise about the timing of each element and the sequence in which they need to be completed in order to complete the whole project in the shortest possible time. This is called critical path analysis, and is some- times referred to as CPA. The critical path is the shortest possible time in which the project can be completed once the timing of each task and the nec- essary sequencing has been taken into account. The activities and their timings can be drawn on a chart that shows the paths that each activity must take and their relationships to each other. In particular, this chart shows the dependencies. Dependencies are when one activity cannot start until another is completed. It is usually the impact of dependencies that slows a project down, and so the dependencies and the resulting sequence need to be iden- tified to establish the critical path (see Figure 8.2).
Scheduling 103
You may need to draw out the diagram several times before you can show the sequence clearly. The sequence of activities in package 1, prepare the site, is the easiest one to draw first because each activity is dependent on the previous one. For example:
࿖ 1.1 (survey site) has to come first.
࿖ 1.2 (plan alterations) cannot happen until the survey information is avail- able and any necessary decisions about building work to be carried out are made.
࿖ Estimates of the costs of building work (1.3) cannot be made until the plans are complete and specifications produced.
࿖ Three estimates must be obtained and a decision made about which builder should be awarded the contract before the contract can be agreed (1.4).
࿖ 1.5 (purchase building materials) cannot be completed until the contract is signed because this is usually done by the builders according to the specification.
࿖ All of this has to be completed before building work can commence (1.6).
࿖ And this sequence has to be completed before the office move can happen.
Package 2, furnish and equip the office, cannot start until the alterations have been planned because these will determine the space in which furniture and equipment will have to fit. Staff will want to understand the opportunities and restrictions of the new office space before they can comment on the fur- nishing and equipment needs in any detail. It is also safer to wait until the alteration plans are complete before starting on Package 3, service prepara- tion, because any staff involved will find it difficult to discuss changes in working practices until they have some idea about the length of time that the service will be disrupted.
There are a number of activities in packages 2 and 3 that can be completed while the building work is in progress, but some cannot be progressed until the new office is ready for occupation. At that stage, the furniture can be installed (2.8) whether it has been moved from the previous location or has been purchased as new. Similarly, the equipment can be installed (2.7) once the electric wiring has been completed, although some equipment may need furniture to be in place first. During the week of the move the normal office service will be covered by a temporary service (3.4) which has to be arranged and resourced in time for that period.
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The service cannot be provided from the new office until all the activities have been completed. Figure 8.2 shows the sequence in which that has to happen and the length of time each activity will take. To find the critical path, you look for the stages in the sequence where something must be com- pleted before others can progress. In this 1.1 (surveying the site) must start first and be followed by 1.2. Once 1.2 (planning the alterations) is complete, a number of other activities can start. These include 1.3, 2.1, 2.2, 2.4, 2.5 and 3.1. These activities all have paths that lead to completion of the building work, but each path takes a particular length of time to arrive at that stage.
The activities in package 1 take the longest in total, with 1.1 to 1.6 taking twelve weeks in total. The next longest (3.1 and 3.6) take only five weeks, and so there is some choice about when these are carried out between weeks five to twelve. Activity 3.5 (Prepare staff locations and rotas) is a little different because that will not be needed until the new office is ready for staff to begin to deliver the service from there, although these matters are usually agreed well in advance because they can arouse strong feelings.
A crucial stage is reached when the building work is complete because the furniture (2.8) and the equipment (2.7) can be installed. During this week the temporary service (3.4) must be provided and everyone who needs to know about the new office location can be informed (3.7). The critical path is the line that takes longest to reach each point at which further activities are dependent. The line in this project is 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, then one week during which three activities take place. This critical path adds up to 13 weeks, by the end of which time the office can be occupied and used.
It is important to have some idea of the length of time the project will take in the early stages of planning if the time of completion is critical. In a project of this nature, it is often possible to reduce the critical path a little by investing more resources. For example, the length of time the building work will take might be reduced if more staff were engaged in the work. Other things cannot be speeded up – for example, it is not usually possible to speed up the drying time of plaster. The installation of furniture and equipment might also be completed more quickly if that becomes necessary, but this might be more expensive. As you can see, the balance of time, cost and quality is always an issue in managing a project.
If you do make changes to the schedule to reduce the length of time taken by one or more of the activities, be careful to consider the impact this has on the critical path. For example, in this diagram it would not create any advan- tage to carry out an activity more quickly if it was not one of those on the critical path. However, if enough time in the activities on the critical path was to be reduced, the path itself might change. In this example, if the current critical path was to be reduced to take less than 14 weeks, the path of 1.1, 1.2, 3.1 – 3.7 might become the critical path, but there are also two other paths Scheduling 105
that would take 13 weeks (the paths to install furniture and equipment). All the estimated times on these paths would have to be considered to establish whether any other time could be reduced so that the shortest possible critical path time could be identified.
Although it is essential to identify dependencies, it is very helpful to estab- lish that these are unavoidable. If one activity is usually completed before another it is not necessarily essential to complete it first, and it might be pos- sible to overlap the activities. It is an advantage to reduce the number of dependencies because that will increase the flexibility available in imple- menting the project.
These examples illustrate the use of this technique in a fairly simple way, and hand-drawn diagrams would suffice to support planning. In more com- plex projects it is usual now to use computer software that helps you to draw these diagrams, and enables the detail of tasks to be included with the activ- ities. The greatest advantage with computer programs is the opportunity to try out the impact of making changes much more quickly than would be possible if each new diagram had to be hand-drawn. However, the time needed to learn to use new software is a consideration for someone who may not often have to manage complex projects. There is also an issue of under- standing, and some people find that puzzling out a hand-drawn diagram helps them to think all of the issues through in a way that does not necessarily happen when feeding the information into a computer. A project manager does not always have a personal choice about what approach to take because of the number of other people who are involved in a project. There is no reason, however, why you should not make your own choice to work things out for yourself before you produce information in the form required by others.
PAUSE FOR THOUGHT
Check your understanding. If a task on the critical path is expected to finish five days early, will the project complete five days early?
The answer is no, because there might be another task that was not critical in the original planning because it would have finished two days before this unexpectedly early one. In this case, this other task now becomes the critical one and defines the expected fin- ishing time, which would now be three days early.
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9
Implementing the project
Implementation is an exciting time for people managing projects. It is the point at which all the planning begins to turn into practical outcomes. The work of a project manager changes at this stage from imagining how things will work into supporting the activities. The focus of attention moves from developing frameworks to monitoring the real activities to ensure that every- thing is progressing as planned. The attention of those managing projects can never stray far from planning because this is the mechanism by which we are able to keep the balance between time, cost and quality. Even when imple- mentation is about to start there is a little more planning to complete to ensure that the transition from planning to activity is smooth and effective.