CHAPTER 4

Model Reviews

4.1 Introduction

This chapter describes types of model review, review processes, model preparation, and reviewer roles and responsibilities. It separates review types into two categories: model structure and composition plus design compliance.

• Model structure and composition includes modeling standards reviews and model integrity reviews. These reviews focus on verifying that model files comply with requirements defined in modeling standards. The following sections discuss each of the reviews in detail, including specific guidance and procedures for conducting design reviews within a 3D model environment.
• Design compliance includes survey reviews, discipline-specific design reviews, and clash detection and spatial coordination reviews. Each of these reviews involves verifying that model elements comply with design standards. The reviews differ in the type of standards being checked against.

4.1.1 Model Reviews According to ISO 19650

ISO 19650-4 provides a high-level workflow for QA and QC performed by the appropriate appointed parties in the execution of a project. To initiate the review process, design data is generated by an information provider for each information container, which is then checked for QC aspects according to the project information standards by an information reviewer. These reviewers inspect the container itself to determine if it meets information exchange requirements such as exchange schema and data format. This essential step needs to happen prior to reviewing information in each container.

The reviewer then examines information in each container to check the LOIN (i.e., the required levels of detail and information for model elements), the appointed party’s information requirements, and any information needed by other task teams. These information reviews verify the quality of data within the container but do not address design considerations. Once the information is reviewed and approved for sharing, an information model review can take place. This is done by the design team, which reviews the federated model according to the information requirements, acceptance criteria, and master information delivery plan or BEP.

The ISO standard is a useful resource for agencies when establishing their quality management program and project delivery standards. ISO 19650-4 provides a workflow but does not specify job aids or criteria for executing checks. Agencies adopting ISO workflows may need to expand their current job aids. The following sections highlight the scope of each review type and the additional resources needed to perform these reviews.

4.2 Model Structure and Composition

Model reviews examine how a model is constructed. A quality model uses the required software configuration or workspace (i.e., combination of settings and content libraries) and properly applies naming conventions, model structure, templates or assemblies, element types, styles, and LOIN. This section introduces two types of model structure and composition reviews: modeling standards and model integrity reviews.

A modeling standards review looks at compliance with the agency’s CADD/BIM/model development standards, and a model integrity review looks at the model structure. These reviews need to be conducted prior to checking 3D models for design compliance. (For core competencies that reviewers should possess and detailed procedures for conducting both kinds of reviews, see Appendix E.)

4.2.1 Modeling Standards Review

Scope of Review

This review is performed on discipline-specific models to check that LOIN and metadata requirements are met and for compliance with BIM/CADD standards. Through this process, model omissions are identified, which the back checker or originator can update.

Review checklists typically include checks such as

• LOIN of elements (i.e., level of geometric detail and level of attached information), as defined in a MET (usually part of the BEP);
• Compliance with BIM/CADD standards; and
• Application of CDE standards (e.g., file structure, reference architecture, file naming structure, file size limits), which may be defined in BIM/CADD standards, model development standards, or the BEP.

Review Information

Table 1 outlines reference standards and other documents required to complete this review.

Table 1. Documents for 3D modeling standards review.

Table 2. Documents for 3D model integrity review.

4.2.2 Model Integrity Review

Scope of Review

In a model integrity review, models from individual disciplines are methodically reviewed along with the federated model, which combines discipline-specific models into a single model. This review verifies that the contents of discipline-specific models and the federated project model comply with geometric and surface accuracy, and it verifies the completeness of each model’s content.

Topics covered by checklists for model integrity reviews typically include

• Federated model structure (e.g., how discipline-specific models are referenced together),
• Structure of discipline-specific models (e.g., types of model elements used),
• Template and corridor definition,
• Density of points in terrain surfaces and along linework,
• Density of template drops in corridors,
• Gaps or overlaps between models,
• All disciplines are using the correct version of the software,
• All disciplines are using the correct coordinate system and units, and
• Confirming boundaries in discipline files.

Review Information

Table 2 outlines the documents required to complete this review.

4.3 Design Compliance

The design compliance review assesses a model to ascertain whether a design complies with applicable design codes, standards, and technical criteria. At a high level, the review process (Figure 7) is fairly simple: Isolate the content in a model, compare it to the standard, document the check, log any issues, and move on to the next element type. A reviewer needs two distinct skill sets to execute these reviews. First, they need the domain expertise to determine whether content complies with standards. Second, they need the modeling skill set to open the file, isolate the content, and view the properties.

This section describes the survey, discipline design, and clash detection/spatial coordination reviews; the scopes of these reviews; and the types of documents and reference standards involved in the reviews. (For more detailed sample review procedures along with the core competencies needed to conduct each type of review, see Appendix E.)

4.3.1 Survey Review

Scope of Review

The survey review is a check for compliance with agency geomatics or survey specifications for developing and delivering models of existing conditions. A number of survey review categories

are typically addressed by a surveyor (or a reviewer with survey knowledge or background). These categories include the survey method, reference frames, geodetic control, topographic and planimetric base models, terrain surfaces, land and mineral boundaries, easements, ROWs, and associated metadata.

Survey Review Categories

• Survey method: The instruments and methods used to collect survey data are suitable for developing and delivering the required level of detail (LOD), precision and accuracy, functionality, and fitness for the intended use of the survey data.
• Reference frame: This is a review of the spatial and temporal characteristics of survey data, including datum (horizontal and vertical), geoid model, projection, scale factors, and epoch.
• Data dictionary/feature codes/layers/levels: Features are assigned to the appropriate feature code, layer, or level and represented correctly in the digital survey files or base map drawing.
• Geodetic control: Location, accuracy, reliability, and stability of the primary and secondary control monuments support construction, compliance with required accuracy and precision for the project, and alignment with the reference frame.
• Topographic and planimetric features: Data on relevant topography and planimetric features have been collected, are representative of existing conditions, have a sufficient LOD for the intended use, and are reflected accurately in a model or base map. This review also verifies alignment with the geodetic control, reference frame, and data dictionary/feature codes/layers/levels regime.
• Terrain surfaces: Terrain models accurately reflect data inputs, such as points, breaklines, and surface boundary; contain neither voids nor other anomalies nor unexpected triangulation; and convey the required LOD for the intended use. This review also verifies alignment with topographic and planimetric data.
• Land/mineral boundaries, easements, property boundaries, and ROWs: 2D land and boundary features and geometry are accurately represented, and the determination and documentation thereof comply with operative jurisdictional laws and regulations and industry standards.

Review Information

Table 3 outlines reference standards and other documents required to complete this review.

Table 4 indicates the applicability of reference standards and other review documents for the defined survey review categories.

Table 3. Documents for survey review.

4.3.2 Discipline Design Review

This type of review checks for a design’s overall functionality and its compliance with project requirements for design standards, design intent and project milestone deliverables, constructability, quantities, and cost estimates. Design reviews specifically check for

• Project requirements: Commitments have been met (e.g., to stakeholders).
• Design codes or standards criteria: Discipline-specific design codes and standards criteria are used properly, as required by agency design manuals, and the design conforms with project milestone requirements. This also includes design elements that may have been omitted or missed, such as missing slope transitions or structural sections.
• Design calculations: The design model matches the engineering calculations, and any model-based calculations are correct based on the design code and standards criteria for the design discipline.
• Constructability: The design is constructable and functional overall. This assessment may include construction staging and interim milestones like traffic switches.
• Quantities: Design quantities entered in the engineering-cost estimate match modeled quantities, and quantities are assigned to the correct pay item number or cost code. This process may be automated if the software provides that functionality.
• Cost containment: Also called a value engineering review, this check assesses design value based on multiple design alternatives for controlling overall cost without compromising the design intent and safety.

Scope of Review

The discipline design review is a comprehensive review of all elements pertaining to engineering standards and design. This review checks whether a model conforms with design codes and calculations, project requirements, and design intent. It follows a series of procedures that verify

• Model objects were developed using the correct design code or criteria (as required by design standards and manuals).
• Model-based design calculations are correct.
• Modeled element dimensions and geometry are consistent with design calculations.
• The design satisfies project scope and requirements.
• Proper documentation exists through all stages of review.
• Modeled items match the pay item schedule and estimated quantities, and omissions are identified.

Review Information

Table 5 outlines reference standards and other documents required to complete this review.

4.3.3 Clash Detection and Spatial Coordination Review

Scope of Review

This review involves analyzing each discipline-specific model to evaluate the position of its model elements in relation to each other and in relation to the model elements from other discipline-specific models. It checks for hard clashes (i.e., direct conflicts), soft clashes (i.e., lack of adequate clearance), and sight distance. The review can also determine whether adequate space for constructing or maintaining design elements has been provided. Checklists can identify specific rules to be conducted or included in clash tests.

Review Information

Table 6 outlines reference standards and other documents required to complete this review.

Table 5. Documents for discipline design review.

Table 6. Documents for clash detection and spatial coordination review.

4.4 Roles and Responsibilities

This section addresses how roles and responsibilities differ for project team members and the types of typical job categories involved in various model-based reviews. (See Section 2.3.2 for the five basic steps for executing a review—initiate, check, back check, update design, and verify changes.)

4.4.1 Project Roles Across Disciplines

The following roles and responsibilities must be fulfilled on each project. On smaller projects, one person may fill multiple roles. For example, a roadway resurfacing project may have the same person assume the roles of project manager, design manager, and roadway discipline lead. When one person occupies multiple roles (e.g., design manager and discipline lead), a peer from outside the project team needs to carry out the independent quality review and audit roles. Some of these roles and responsibilities may be new to an agency, such as CADD/BIM manager

4.4.2 Review Preparation

Any qualified person may prepare the documents that will be reviewed except for the individuals who will conduct the review and audit the review process. The project quality–management plan should identify the reviewers and the scope of the review at each milestone. Basic tasks involved in preparing a model for a review are shown in Figure 8.

4.4.3 Reviewer Selection

The review types in Sections 4.2 and 4.3 are organized according to the primary skill set needed to execute the reviews. Design compliance reviews require a primary design skill set with secondary skills in navigating and manipulating 3D model content. Model integrity and modeling standards reviews require a primary 3D modeling–skill set with secondary skills in the discipline. When selecting a reviewer for 3D plans, a minimum level of experience is required to check design work—just like reviewers for 2D plan workflows. Agencies can define the minimum qualifications and experience of reviewer roles and how they relate to each other using the appendices in this guide.

At the time of writing, some of the most-qualified design managers and discipline leads do not have the skills required to use 3D models. 3D modeling tools became widely used after the responsibilities of many current practitioners transitioned from active design documentation to overseeing the design documentation process. Another challenge is that software products focused on reviewing, rather than authoring, 3D models are still emerging. Currently, there is no software product that supports the limited 3D modeling–skill set of a typical design reviewer; even for expert reviewers, the products do not have all the tools necessary to review models. (See Section 6.4.1 for more on review software functionality.)

Appendix D provides a set of 3D modeling–core competencies for each review type. Agencies can use information in this appendix to develop training programs for design reviewers. It also contains resources that can help software developers bring design-review tools to market that have a much lower barrier to use than 3D model–authoring software.

By documenting core competencies clearly with the review procedures, project teams can more easily locate individuals with needed skill sets, and reviewers can more readily determine if they need support to execute a review. For example, a design reviewer can direct another person to manipulate a model for them, enabling them to thoroughly review the design. This practice has utility while reviewers are upskilling to acquire necessary core competencies for software,

but it should not be a long-term solution. Agencies can use the core competencies to develop a skills-based training curriculum for reviewers, utilizing defined quality management processes and sample datasets. (See Section 6.3 for trainings and workshops that agencies can use to implement the guide.)

4.4.4 External Review Preparation

External reviewing agencies (e.g., permitting agencies) have their own requirements for submittals. Some may not be able to receive model-based submittals. External review requirements should be planned for in the project BEP and prepared and reviewed alongside other deliverables. Consider the following points when developing processes for external reviewing agencies:

• Determine how external agencies will review 3D model information, and determine whether a 2D PDF needs to be developed and extracted from the 3D model. This additional step should be included in agency procedures.
• Identify new responsibilities or competencies for external agencies to review 3D models at milestones, and decide how training would be conducted.
• Identify agencies that may not have resources to revise 3D models. For example, state DOTs may encounter utility agencies that lack the resources to receive, interpret, and use 3D model data. In some cases, shapefiles may offer a middle ground that is accessible. Another option is for DOTs to develop an industry-specific user group for an industry that lags in the development and usage of 3D design detail. This format offers small and large utility owners an opportunity to interact with and support one another, under the coordination of DOT staff.

4.5 Review Process and Preparation

This section describes how the addition of 3D model–based design reviews affects the traditional quality management timeline. It addresses similarities and differences in preparing for milestone reviews and discusses risks associated with 3D model–based deliverables and mitigation strategies. This section also discusses the need to establish standardized clash routines.

4.5.1 Review Timeline

All the various types of reviews are part of an overall review process timeline. Agencies typically develop milestone deliverables, at which times formalized agency reviews occur. These reviews typically happen at core design stages (e.g., 30%, 60%, 90%, 100%). Milestone reviews are typically led by agency reviewers or completed and documented by a consultant team.

The design team should thoroughly and routinely check their work prior to milestone reviews. The recurring schedule and identified reviewers for each review type are documented in the BEP. For example, early and incomplete 3D modeling may be shared with geotechnical staff so plans for a geotechnical investigation can be developed, executed, and returned to the project manager. Geotechnical feature details may be incorporated in several ways as the final 3D model evolves. One method is for geotechnical staff (either in-house or consultants) to use early model data and add subsurface investigative results and interpolated features, returning the updated files to the project manager for further use. Geotechnical data may also be delivered in raw form and incorporated through CADD staff assistance. These methodologies are highly dependent on the capacity and expertise of staff, including the timing of resource allocations within a broader project development process.

While agency milestone reviews typically happen at specified intervals based on design progress or completion, survey is complete before the design initiates. As such, a modeling

Review protocols can be organized as checklists or supplemented with checklists. The goal is to have a repeatable, reproducible way to check designs and models that implements the quality management process consistently and rigorously. (Sample review procedures can be found in Appendix E.)

Consider the following when creating review protocols:

• Automations should be thoroughly tested before being incorporated into standard review procedures. If a reviewer develops their own automations, they should demonstrate that the results are reliable. Examples include preset clash detection routines and reports generated by software.
• Automation and process control are effective strategies to identify and contain high frequency, low-impact issues. Examples include spelling errors, CADD standards compliance, metadata contents, and file naming conventions. Originators should run these checks before submitting a packet for review.
• Protocols should consider ergonomic issues like automation complacency and boredom when performing repetitive tasks. Reviewers should be guided by job aids (e.g., checklists, step-by-step procedures) to inspect for risks with the highest impact and aided by well-tested and thoughtfully formatted reports for tedious checks, like geometry comparisons between calculations and the model.
• Generating a review artifact that provides a record of what was checked, when it was checked, and who checked it.

4.5.4 Standardizing Clash Routines

The scope of and reference documents for clash detection are provided in Section 4.3.3, and sample clash detection–review procedures are available in Appendix E. BIM software will check for clashes between elements within both current and referenced models based on specified requirements. Designers and reviewers can create unique clash routines—a sequence of requirements to check—at any time. A clash routine analyzes elements with specified properties (e.g., levels/layers, attribution, object classification) for compliance with spacing and overlap rules.

Making standard clash routines available to reviewers will establish a repeatable process while improving efficiency. As long as designers correctly apply CADD standards, namely using the correct levels/layers when modeling, standardized routines can be part of review protocols. Depending on skill sets and available software, these routines can be run by either reviewers or designers, who then provide a clash detection report in the review package. Designers can also run clash routines throughout the design process to detect and address issues early in the development process.

Ideas for standard routines include checking utility facilities for

• Hard clashes and clearance requirements,
• Hard clashes between steel reinforcement,
• Concrete clear cover around steel reinforcement, and
• Element overlap between phasing models to evaluate construction staging.

Agency standards and design manuals define clearance and spatial requirements. These requirements can inform standardized clash routines or rule sets that may be imported into a new routine to save users the hassle of beginning from scratch.