What are the most common CPM scheduling mistakes in civil engineering?

Failing to account for potential delays, changes in scope, or unforeseen circumstances can lead to an inaccurate schedule and costly delays.

Common CPM (Critical Path Method) scheduling mistakes in civil engineering include inadequate task sequencing, inaccurate duration estimations, insufficient resource allocation, lack of contingency planning, and poor communication among project stakeholders.

I would like to add that part of ‘ignoring constraints’ is often ‘ignoring reality’. Usually this is the case with overly excited entities, clients who are too much focused on given promises (usually politically or hierarchically motivated). However, activities take time and the laws of physics still apply and days have only 24 hours. Having said this, of course, value engineering and thinking outside the box can improve or benefit the schedule.

Mistake 2: Overlooking constraints can lead to unrealistic scheduling assumptions and hinder project progress in civil engineering CPM scheduling.

Not considering resource constraints, such as limited manpower or equipment availability, can result in unrealistic schedules that are difficult to achieve.

In order to achieve a realistic CPM , the network graph have to be constructed so that there is only one activity without a predecessor and only one activity without a successor, except for activities that designate reference points or activities for which a conditioning relationship cannot be established. The level of detail of the activities have to be chosen so that their duration does not exceed 30 calendar days ( or something near). The sequence of activities have to be established taking into account all the constraints.

An example I have seen as a usual scheduling mistake is assumptions used to quantify labors/machinery production rates, Companies should rely on historical labors or machinery production rates to calculate level of effort needed to complete the tasks. Most schedulers use standard or assumed rates that matches available durations to finalize master schedule, Therafter baseline becomes un-realistic and soon needs to be revised.

Once the CPM schedule has been created and transmitted into an accessible format, it undergoes an approval process. Construction schedulers tend to severely underestimate the length of this submittal-approval process, which involves detailing, preparation, issuance of submittals & resubmittals.

Mistake 3: Using unrealistic assumptions, such as underestimating task durations or overestimating resource availability, can lead to inaccurate scheduling in civil engineering CPM. This oversight may result in missed deadlines, increased costs, and compromised project quality. It's crucial to thoroughly assess and incorporate realistic factors, such as project complexity, resource constraints, and external dependencies, to ensure an achievable schedule.

Making assumptions about project timelines or resource availability without proper data or analysis can lead to unrealistic scheduling and potential project delays.

Mistake 4: Failing to communicate effectively among project stakeholders can lead to misunderstandings, coordination issues, and delays in civil engineering CPM scheduling. Clear and consistent communication is essential for ensuring alignment on project goals, resolving conflicts, and maintaining progress according to the schedule.

Lack of communication between project team members, stakeholders, and subcontractors can lead to misunderstandings, delays, and costly mistakes in the schedule.

Keep it simple. The critical path method is confusing for many construction professionals, and may be entirely foreign to owners and investors. Presenting construction schedules in a user-friendly format is necessary in order for owners (and their associates) to provide educated opinions during the early stages of scheduling.

Mistake 5: Neglecting to prioritize quality control measures within the scheduling process can compromise the accuracy and reliability of civil engineering CPM schedules. Overlooking quality assurance can result in errors, rework, and ultimately, project delays and budget overruns. Integrating quality checks and validation procedures throughout the scheduling process is crucial for ensuring the integrity and effectiveness of the project timeline.

Prioritizing schedule adherence over quality control can result in subpar work and potentially rework, which can lead to project delays and increased costs.

Complex construction projects sometimes necessitate overlapping operations, and aggressive timelines require schedulers to visualize a complex sequence of activities involving multiple trades. However, orchestrating overlap has many dangers. Too much overlap causes congestion and lower output, while too little means inefficiency. Executing the ideal balance necessitates not only meticulous CPM scheduling, but also the collaboration of all contracted teams.

Mistake 6: Forgetting to learn from past projects and continuously improve scheduling methods can hinder progress in civil engineering CPM. Failing to analyze and adapt based on previous experiences may lead to repeated mistakes, missed opportunities for optimization, and ultimately, reduced efficiency in project scheduling and management.

not accurately identifying the sequence of activities, leading to flawed critical path analysis and when project timelines are not based on realistic assessments which cause delays then leading to unrealistic duration estimates. Then not assigning the right resources to tasks, which hinders progress and causes delays.

what else to consider: - no contiguous critical path:if the path to the end of a project is incorrect, then the schedule is of no value to be used to drive a project. -negative float:technically negative float means that the late schedule is before the early schedule, which is wrong.Schedules can’t be run with negative float. -wrong updates (of actual progress):Incorrect entry of actual progress on tasks(most common problem). -date constraints:you want early warning while there is enough time to make corrections, but the schedule should not be restricted by date constraints. -no successors : you can fix the negative float problem by deleting the Finish-to-Start dependencies no longer valid, but this introduces this mistake — no successors.