Updated: Mar 28
4D planning is an industry practice that combines two deliverables many project teams already have: the project schedule and a 3D model. The 4D model allows stakeholders to visualize their schedule in a 3D space, which empowers engagement, communication, and decision making throughout the project lifecycle.
Those of us accustomed with project scheduling are all too familiar with the Gantt chart, coined in 1910 by Henry Gantt. Yes, you read that correctly, 1910. The Gantt chart is a bar chart that illustrates a project schedule in a visual manner. If you have ever had the pleasure of sitting through schedule review meetings on past construction projects, then you are likely aware that the format can be difficult to follow on a scope of any substantial size. Stakeholders often struggle to follow logic and linkages; some team members simply disengage. This is all too common within construction teams.
The downside to this disengagement includes trades and contractors not understanding or following the schedule, out of sequence activities, missed activities, and poor cost and schedule performance. Poorly planned or out-of-sequence work can also result in execution risks and injuries, as well as quality issues. Planning is a key factor in successful project performance. Teams need fit-for-purpose tools that facilitate effective planning in a manner that makes information accessible and engaging. These tools, in turn, empower them to make decisions and positively impact performance outcomes.
Unfortunately, the tools and processes most frequently used for project teams to execute granular planning haven't changed in decades. Large project schedules contain hundreds if not thousands of activities. It doesn't matter how much scheduling experience you have; following the logic in a Gantt chart with 10,000 activities is nearly impossible. How then do teams facilitate task-level planning? The reality is, they often deviate from the schedule in favor of to-do lists, Trello boards, or sticky notes.
Schedules have their place on projects. They can't be replaced, but they can be augmented to improve collaboration and performance in engineering, procurement, and construction. 4D planning has revolutionized the scheduling process, allowing teams to better collaborate and visualize information in a 3D environment. And, teams that are leveraging 4D planning are proving that these programs not only improve schedule understanding and accuracy, but also reduce cost growth, improve schedule durations, reduce rework, and reduce risk to workers in the field.
Humans are Visual
At least 65% of us are visual learners. As such, many project stakeholders will engage more effectively with data that is displayed using effective visual means. Think back to the last presentation you attended. Was the content mostly text slides or mostly graphics? How many of those text slides do you recall? Was the audience engaged with the content as presented, or were many participants more actively engaged in side conversations or with their mobile phones?
Since many of us prefer visual content, we can leverage this preference to engage project stakeholders with the 4D model. Rather than presenting construction teams with lengthy schedules and Gantt charts, we can present an immersive 4D model that can be navigated and manipulated on demand. Within a collaborative setting, teams often find that stakeholders will naturally center around these visual planning solutions, thereby prompting more active involvement in plan development and review sessions.
How a 4D Model is Produced
Utilizing a 4D planning solution, the 3D model and the construction project schedule are imported to build the baseline 4D model. 4D solutions support a multitude of schedule file types. Therefore, you likely won't need to change your scheduling solution to implement 4D planning on your project.
3D model files sometimes require pre-processing prior to importing into the 4D solution. Depending on the Level of Detail in your model, your current 3D architecture may suffice or may need to be adjusted to enable ease of 4D model development and long-term maintenance. Once your 3D files are imported, the individual tasks within the schedule may be linked to their corresponding components within the 3D model to produce the 4D sequence.
Automated Element Synchronization
If the model has been attributed to support linkage with schedule activities, 4D model development and updates can be automated. Synchronization requires a common attribute to link the 3D model element and the schedule activity; elements may be synchronized upon upload of the model and schedule files to the 4D environment.
Manual Element Synchronization
Without the ability to automate synchronization of the model elements and schedule activities, teams must manually attribute 3D model elements to develop their 4D model. This is a time-consuming and labor intensive task, and at scale, becomes unmanageable. On large projects, proper model attribution and schedule activity coding is necessary to support effective 4D model management. At the beginning of any 4D pilot, teams should develop a 3D model specification and 4D procedure to ensure that the project team understands the deliverables and requirements necessary to support the 4D program, which will in turn reduce the overall cost of the 4D program.
Model Based Scheduling
Another process or technique for creating a 4D schedule is to use the 3D model as the basis for creating a schedule. This is an effective way to create a construction schedule as the visual representation of the model ensures that construction activities are not missed during the planning process. For example, a 12” high concrete retaining wall that is to be poured around the perimeter of a building may have been missed in the contractor's schedule. This is a substantial task to be missed; if not coordinated this may result in congestion, area access limitations, and out-of-sequence work . Missing this task in the schedule would also undoubtedly affect the construction completion date. By creating the construction schedule in the 4D model environment using model-based scheduling, the team can ensure that all model elements have been planned and sequenced.
How a 4D Model is Managed
Updating the 4D model requires frequent and repeated data loads, usually weekly or bi-weekly as the model maturity evolves and schedule data is updated. The 4D model administrator loads the new data and validates the model attribution. Non-linked tasks are linked, and schedule data is verified against the base schedule file. Once complete, the 4D model is ready for use by the project team, current with the latest project data.
Model Based Progressing
An additional advantage of 4D, is the ability to progress tasks in near real-time. For example, a component within the 4D model, such as a pipe spool, can be selected and progressed upon completion by the responsible Foreman. Furthermore, rules of credit can be established to further delineate the progress of tasks. Once the spool has been staged near the installation location, 20% credit can be earned toward the overall completion of the task. Progress is updated seamlessly, instantly, and efficiently, reducing paperwork, and allowing supervisors to spend more time in the field with their crew. All that is required is a connected 4D environment, internet connection, a bit of training, and harware.
Once the schedule is attributed to the 3D model, 4D solutions have the capability to render many types of animations, exportable as videos for broad distribution. These animations can be used to facilitate constructability reviews, construction optimization analysis, project presentations to the project owner or stakeholders, and task level planning with construction crews. Popular animations that are often created on projects include, planned vs actual, look-aheads, and the overall construction sequence. Animations can be rendered by different views and filtered by the Work Breakdown Structure or by construction discipline.
By rendering a planned vs actual scenario, teams can view if the project is on schedule. If the project happens to be off schedule, teams can easily see which tasks were off-plan. Subsequently, a plan can then be derived to realign the tasks with the required completion dates.
Another popular animation that can be rendered is the “look ahead.” Tasks can be filtered by a specific date, showcasing which tasks are scheduled to start, are in progress, or have been completed. These animations are useful for construction crews as they can be used to plan upcoming work.
The most popular animation is the planned overall construction sequence. This animation is typically filtered by area or by discipline. The main feature of this animation is the ability to show the overall construction sequence to facilitate schedule awareness, optimization, or constructability reviews.
4D Planning Benefits
The benefits of 4D planning are substantial. Just ask any front-line supervisor or project manager that is currently using 4D planning on their project. Ultimately, 4D models allow us to visualize what we are constructing before we step foot on site, which provides teams the capacity to communicate the schedule visually and quickly to all stakeholders. This, in turn, allows us to identify schedule errors or inefficiencies, which may result in risk to workers, cost impacts, or schedule impacts.
Beyond the inherent benefit of project plan visibility, the following benefits are realized by teams that are deploying 4D planning programs on construction projects:
Improved understanding of the execution plan
Ability to identify out of sequence work
Reduction in risk to workers due to improved risk identification and mitigation
Reduction in out-of-sequence work which often results in cost and schedule impacts
Improved collaboration between construction contractors and trades
Improved productivity due to enhanced spatial planning
Reductions in equipment costs resultant from 4D equipment planning
Clear visibility of progress lag and ability to mitigate risk of delays
Equipment can be placed in the 4D model allowing for resource optimization, such as cranes, JLGs, etc. While beneficial for equipment planning, teams can also complete virtual dress rehearsals in 4D to conduct a full walk through of a heavy or critical lift in advance of the work. This empowers teams to walk through the process step by step, ask questions, and identify and mitigate concerns and risks.
Most importantly, 4D planning can reduce risks to workers and improve project safety performance by instilling a collaborative approach to planning within the project team. 4D models can be leveraged to identify safety risks prior to, and throughout, the construction process. Teams may then use this early planning time to implement preventative measures to avoid accidents. By shifting the timeline of risk identification earlier, and from the field to the office, teams can be proactive in reducing the potential of risks to workers and help ensure that everyone goes home safely at the end of each shift.
Research conducted by F.H. Griffis and C. Sturts has documented that "using 4D models resulted in an average of 5% savings in cost growth, 4% savings in schedule growth and 65% reduction in rework". (Griffis & Sturts, 2003). Minimizing schedule delays and cost growth is critical for all project stakeholders to ensure project success. The substantial reduction in rework can help turn a minimally profitable project into a profitable project; in the highly competitive construction market, where tight margins are common, executives are taking note of the potential for 4D to drive bottom-line organizational improvements.
Gledson and Greenwood (2016) completed an assessment on adoption of 4D in the UK. "The results indicated a significant relationship between the size of a company and the adoption of BIM as well as a link between the use of 4D and the companies' maturity. The research showed that 52.9% of participants surveyed, worked for companies using 4D on current projects and almost 70% of those surveyed believed that 4D could “add value to their business.”
The UK has been at the forefront of 4D implementation and adoption and have been reaping the rewards. Although other countries such as the USA and Canada have been lagging in their adoption, more companies are successfully implementing 4D programs year after year. However, considering the commonly cited challenges in project cost and schedule performance in the construction industry, it is expected that 4D planning will continue to gain momentum and see adoption increases year over year in the North American market.