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Critical Path vs Longest Path

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John Reeves
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Consultant said the longest path was the Critical Path "The attached longest path goes through the Package 2 permit, followed by the Caisson work for D, then E with the remainder of the building work for Area E through March 28th into Punchlist and Turnover." I ran the Float Path listing -  The critical path goes through package 2, then through Area C is shown completing on May 1, 2023 which is the Substantial Completion".  I think the path that goes to Substantial Completion is the crit path not to the last item on the schedule  Chances are they need to change their logic.

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Patrick Weaver
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The critical path is NEVER defined by float.  Some software allows colour to be added to bars based on a float value but this does not define the critical path.  There are several definitions of the 'critical path', none of the authoritative ones used float. For more on this see: Defining the Critical Path at: https://mosaicprojects.com.au/PMKI-SCH-012.php#Process5

Azhar Hassan Abbas
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The longest path definesthe Overall Duration of the Project whereas the Critical Path represents the longest continuous chain of activities which establishes the minimum overall Project duration.

Criterian for Criticality can be defined / fixed in the tool depending upon requirements. 

Kannan CP
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Hi Patrick,

Regarding the connection of critical path with float, in P6, there is an option to define the critical path based on the float available for each activity. We can inerpret critical path in other ways as well, relating the path of activities with contract completion date, or interim completion date etc.

Patrick Weaver
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The 'longest path' and the critical path can often be different. The longest path is a fact, it is the logical sequence of activities with the greatest overall duration.  This will be the critical path if there are no other factors in play such as delayd access to elements of the work (eg, access to site is contracted at a specific date seveal months after the contract starts to allow procurement), and/or several contracted completion dates. 

The critical path has nothing to do with float, most definitions consider the effect of the effect of a sequence of activities on a contracted completion event. If there are several contract completion events (handovers), each will have a critical path - the sequence of activities controlling that event).  

Unfortunately there are many definitions of 'the critial path' these are discussed in our White Paper Defining the Critical Path that can be downloaded from: https://mosaicprojects.com.au/PMKI-SCH-012.php#Process5

Kannan CP
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Longest path determines the string of activities that are required to be completed, as per the program logic, in order to reach the final completion date of the project.

Critical path depends on the settings in total float or based on the interim milestone settings with constraint dates.

Kannan CP
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Longest path determines the string of activities that are required to be completed, as per the program logic, in order to reach the final completion date of the project.

Critical path depends on the settings in total float or based on the interim milestone settings with constraint dates.