During the development of a vehicle or component, it is generally not possible to move directly from a CAD model to mass production. At different stages, engineering teams need physical specimens to evaluate design, performance, assembly, interfaces between components, failure modes, and compliance with technical requirements. In product development terminology, these specimens are commonly referred to as Prototypes. However, Prototype does not represent a single, universally standardized maturity level across the automotive industry. A specimen classified as an Engineering Prototype by one company may differ in purpose and maturity from a specimen with the same designation at another company.
This distinction becomes particularly important when planning tests. A label such as Prototype, DV Sample, or Production-intent does not, by itself, determine how applicable the test results will be to the final product. It is necessary to understand the specimen's configuration, which characteristics represent the target design, which elements are still temporary, and which requirement the test is intended to evaluate. A prototype may be suitable for evaluating geometry but may not represent the final product in a test that depends on material properties or manufacturing processes. Therefore, specimen suitability must be assessed according to the test objective.
What Is a Prototype?
In general engineering terms, a Prototype is a specimen built before final production to investigate, develop, or evaluate a product. Prototypes can range from simple models used to assess geometry and packaging to complex assemblies that closely resemble production products. Some prototypes are designed to answer a limited engineering question, while others support a broader range of Verification and Validation activities.
An important point is that there is no single global classification of prototypes followed identically by all vehicle manufacturers and component suppliers. Terms such as Concept Prototype, Engineering Prototype, Mule, A-Sample, B-Sample, C-Sample, Validation Prototype, or Pilot Sample may have different definitions across organizations. For this reason, professional projects should define Sample Maturity according to their own project criteria, rather than making testing decisions based solely on specimen labels.
Why Are Prototypes Built During Vehicle Development?
A prototype is a tool for learning and identifying problems before the product design is finalized. Some engineering questions can be answered through calculations and simulations, but at many development stages, physical or functional specimens are needed to evaluate more realistic product behavior. Assembly and packaging, ergonomics, mechanism functionality, structural behavior, thermal and electrical performance, and interactions between subsystems are examples of areas that may require prototypes.
The main advantage of a prototype is that it enables problems to be identified while design modifications are still easier and less costly. A prototype failure can be extremely valuable if it reveals a design weakness before production tooling is manufactured or mass production begins. Therefore, the purpose of building a prototype is not necessarily to pass a test; during development, generating information for engineering decision-making may be the more important objective.
What Is Sample Maturity?
Sample Maturity describes how closely a specimen approaches the target project configuration. However, maturity should not be described solely by a percentage or stage designation. A specimen may have reached its final state in some characteristics while remaining under development in others.
For example, component geometry may be finalized while the material remains temporary. Hardware may represent the intended production product, while the software is still a development version. Similarly, a component may be manufactured using production tooling, while the manufacturing process has not yet stabilized under final production conditions.
Therefore, the more precise question is not “What percentage of this specimen is final?” Instead, it is necessary to determine how closely the characteristics affecting the relevant requirement represent the target configuration.
What Is Sample Representativeness?
One of the most important concepts in selecting a specimen for testing is Sample Representativeness, or the extent to which the specimen represents the target product. A specimen is suitable for a Verification activity when the characteristics affecting the relevant requirement adequately represent the target configuration.
Suppose the objective is to evaluate the packaging of a component within a limited vehicle space. If the specimen geometry is accurate, the use of a temporary material may not be particularly important. However, if the same component is used for structural strength testing, material properties, thickness, joints, and manufacturing processes may significantly affect the result.
Therefore, a specimen may be representative of the final product for one test but not for another. This principle should guide specimen selection throughout the development process.
What Is a Concept Prototype?
During the early stages of development, a specimen may be built to evaluate an initial Concept. The objective may be to assess packaging, geometry, ergonomics, mechanism movement, or the feasibility of an idea. Such a specimen is not necessarily manufactured using the final product's materials or manufacturing processes.
Rapid manufacturing methods such as machining, 3D printing, or manual assembly may be used to produce these specimens because the primary objective is rapid learning and concept evaluation. If an engineering team can identify a packaging problem using a simple specimen before investing in production tooling, the prototype has fulfilled its purpose.
However, the results obtained from such a specimen should only be interpreted within the scope of the evaluation objective. A successful Concept Prototype does not necessarily mean the product is ready for production.
What Is an Engineering Prototype?
The term Engineering Prototype is commonly used for a specimen that engineering teams use to develop and evaluate a design, although its precise definition should be established according to the organization's development process.
This specimen may be closer to the target design than a Concept Prototype in terms of geometry, materials, or functionality and may be used for development testing, interface evaluation, or failure analysis. However, some components, manufacturing processes, or software versions may still be temporary.
Therefore, when receiving an Engineering Prototype for testing, recording its designation alone is not sufficient. It is necessary to identify which characteristics of the specimen are representative of the target design for the intended test.
What Is a Mule Vehicle?
In automotive development, the term Mule or Development Mule refers to vehicles used to develop or evaluate new technologies and subsystems before the final vehicle design is available. A new powertrain, chassis component, electrical system, or software may be installed on another platform or body to allow development activities to begin earlier.
The appearance of a Mule does not necessarily represent the final vehicle, and its interfaces between components may also be temporary. Its value lies in allowing engineering teams to evaluate the intended system's performance before a complete vehicle prototype becomes available.
However, results obtained from a Mule can only be generalized to the extent that its configuration is representative of the target product for the requirement being evaluated. Such a vehicle does not automatically represent the final vehicle Type.
What Is a Buck?
In the automotive industry, the term Buck is used for certain physical models or structures developed during product development. Depending on the project objective, a Buck may be used to evaluate component packaging, interior layout, ergonomics, or other geometric characteristics.
A Buck is not necessarily a functional or drivable vehicle and may represent only the required sections of the cabin or vehicle structure. Therefore, its evaluation results should be interpreted within the intended purpose of the specimen.
As with other product development terms, the precise definition of a Buck may vary between organizations, and one company's internal definition should not be generalized to the entire automotive industry.
Is a 3D-Printed Prototype Representative of the Final Component?
The answer depends entirely on the requirement being evaluated. 3D printing enables rapid production of component geometry and is useful for many packaging, dimensional fit, and concept evaluation activities. However, the material properties and manufacturing characteristics of a 3D-printed component are not necessarily identical to those of the production component.
If the test objective involves strength, fatigue, thermal behavior, or another characteristic affected by material properties and manufacturing processes, the specimen's representativeness must be assessed. A 3D-printed component may be suitable for dimensional checks but unsuitable for structural strength Validation.
Therefore, a prototype manufacturing technology is not inherently good or bad; its suitability depends on the engineering question.
What Does Production-intent Mean?
The term Production-intent is generally used for a specimen or configuration whose relevant characteristics are intended to represent the target production product. However, it is important to identify precisely which characteristics have reached the intended production state.
Geometry and material may be finalized while the software remains under development. A component may be manufactured using production tooling, while the manufacturing process has not yet reached final production conditions. In another specimen, the hardware may be finalized while system calibration continues to change.
Therefore, the term Production-intent is not sufficient without further explanation. The Test Plan should identify the maturity level of the characteristics that affect the test result.
What Is the Difference Between a Prototype and a Production-intent Sample?
Prototype is a broader term for specimens used during product development, while Production-intent generally indicates that the specimen is closer to the target production product in relevant characteristics. However, the exact distinction between these terms is not identical across all organizations.
The actual difference for testing cannot be determined from the specimen's designation alone. Material properties, geometry, manufacturing processes, supplier, hardware, software, and other relevant parameters must be assessed.
For structural testing, material properties and joint configuration may be particularly important. When evaluating software functionality, the software version and electronic control unit configuration may be more critical. The test objective determines which aspects of specimen maturity matter.
What Is a Pilot Build?
The term Pilot Build is generally used during stages closer to production for building specimens or assemblies that can support product and manufacturing process evaluation. However, its exact position within the development process varies between companies.
Pilot specimens may be used for certain Validation activities or production readiness assessments, but the Pilot designation alone does not establish that a specimen represents the final product at the Start of Production (SOP) for every requirement.
Therefore, when using a Pilot Sample, both the product configuration and the manufacturing process status should be recorded.
Do A-Sample, B-Sample, and C-Sample Have Universal Definitions?
No. These terms are used in some industries and supply chains, but their definitions may vary between customers, suppliers, and organizations. Therefore, a general table describing A-Sample, B-Sample, and C-Sample should not be treated as a universal automotive industry classification.
If a project uses these designations, the project's internal definitions should specify the characteristics and maturity level associated with each stage.
This approach helps prevent misunderstandings between vehicle manufacturers, suppliers, and laboratories.
What Is a DV Sample?
During Design Verification (DV), the specimen should adequately represent the target design in the characteristics relevant to the requirement being evaluated, so that verification of the design against that requirement is meaningful.
However, there is no single universal definition of a DV Sample. Specimen specifications must be determined according to the test. If the requirement concerns geometry, dimensional representativeness is important; if structural performance is being evaluated, material properties, joints, and other relevant characteristics must also be appropriate.
For this reason, a specimen may be suitable for one DV activity while lacking sufficient maturity for another.
What Is a PV Sample?
During Production Validation (PV), greater emphasis is placed on a product whose relevant characteristics and manufacturing processes are closer to the target production conditions. The supplier, production tooling, manufacturing process, and assembly conditions may become more important depending on the requirement.
The objective is not only to evaluate the design using an engineering specimen but also to generate appropriate evidence about the performance of a product manufactured using the intended production process.
However, the precise definitions of PV and Production-intent Samples should be derived from the organization's own product development process rather than from a general rule.
The article “What Are DV and PV in the Automotive Industry? From Design Verification to Production Validation” explains the different objectives of these stages and the required specimen maturity levels.
What Role Do Prototypes Play in Pre-Testing?
Prototypes are one of the primary tools used in Pre-Testing. Before using a final specimen or proceeding with an expensive test, engineering teams can use prototypes to evaluate design behavior and identify potential failure modes.
For example, a development specimen may be tested to identify which areas of a structure experience greater deformation or which component fails before others. This information can be highly valuable for design improvement.
However, if the prototype differs from the target design in characteristics that affect the result, those limitations must be considered when interpreting the outcome. Passing a Pre-Test on a prototype does not guarantee that the final configuration will pass.
Does Passing a Prototype Test Mean the Final Product Will Also Pass?
No. A test result provides evidence only about the configuration that was tested. If the final specimen differs in material, manufacturing process, supplier, software, geometry, or interfaces, the impact of those differences must be assessed.
The more representative the prototype is in relevant characteristics, the greater the confidence that may be gained from testing. However, representativeness must be evaluated against the specific requirement.
For this reason, the Test Report or project records should clearly identify the specimen and configuration to which the result belongs.
Is Prototype Failure Necessarily a Bad Outcome?
Not during development. Prototypes are built to identify problems before production, and their failure can provide valuable information about design weaknesses.
The important point is that failure should not be reduced to a photograph of a broken component. Test data, failure location, load path, material properties, and other relevant factors must be investigated to identify the Root Cause.
If a prototype fails at an appropriate development stage and the engineering team uses the findings to improve the design, the specimen has effectively fulfilled one of the main objectives of product development.
How Should Prototypes Be Managed During Destructive Testing?
If a test may damage or permanently alter a specimen, it should be determined before execution whether that specimen is also required for other activities. Specimen allocation and test sequencing are particularly important in this situation.
Vehicle, battery, body, seat assembly, and other complex system prototypes can be expensive and limited in number. Using a valuable specimen for an unsuitable test can result in the loss of both hardware and development time.
Therefore, before destructive testing, it should be clear what evidence the specimen is being used to generate and what further use, if any, is expected after testing.
Why Is Configuration Management Critical for Prototypes?
Prototypes generally change more rapidly than production products. Two vehicles may look identical but have different ECU software versions, component revisions, or calibrations.
If the configuration is not recorded, it may later become unclear which design the test result belongs to. Part Number, design revision, software version, supplier, or other characteristics may be necessary for traceability, depending on the test.
This becomes particularly important in projects where several prototypes are used simultaneously. A result without properly documented specimen identity has reduced engineering value and usability.
Must All Components of a Prototype Have the Same Maturity Level?
No. A vehicle prototype may contain components and subsystems at different maturity levels. The body may be close to production status, while the electronic control unit remains a prototype and the software is still under development.
Therefore, an overall vehicle designation cannot describe the maturity of every subsystem. For each test, the relevant components and interfaces must be identified, and their maturity levels assessed.
This is increasingly important in modern vehicles, where a significant proportion of functionality depends on software.
Why Is the Software Version Part of a Prototype's Identity?
In software-intensive systems, a software change can alter vehicle behavior without any visible physical modification. Therefore, the Vehicle Identification Number (VIN) or hardware Part Number alone may not always be sufficient to define the specimen.
If a test depends on software functionality, the software version and, where relevant, system calibration must be traceable. Results from a previous version cannot be applied to a new version without assessing the impact of the changes.
For this reason, configuration management in modern vehicles includes both hardware and software.
What Is the Role of Prototypes in Standards-Based Testing?
A prototype can be highly useful for development testing performed according to a standardized test method. Before the main test, the engineering team can assess how closely the design meets the requirement and identify potential problems early.
However, if the activity is intended for Type Approval or another formal process, the specimen must meet the requirements of that process. Whether a development prototype is acceptable for formal testing cannot be determined by a universal rule.
Therefore, it is important to distinguish between using a standardized test method and the regulatory purpose of the test. Applying a procedure from a regulation during development does not automatically make the activity an official Type Approval test.
What Is the Role of Prototypes in Type Approval?
In the Type Approval process, the specimen must represent the intended product Type within the framework of the applicable regulation. Therefore, the designation Prototype alone does not determine whether a specimen is suitable for this process.
If temporary components, non-final software, or a different configuration are present, their impact on the definition of the product Type and the approval requirements must be assessed.
Decisions regarding specimens used in formal approval processes must follow the applicable regulation and the procedures of the Type Approval Authority and designated Technical Service.
How Should Sample Maturity Be Recorded in the Test Plan?
The Test Plan should specify the required specimen and configuration for each activity. The expression “one Prototype” generally does not provide sufficient information.
If production material is required, this should be documented. If a specific software version is necessary, that version should be identified. If the test must be performed on a component from the intended supplier with production-representative characteristics, this requirement should also be established before the specimen is built.
This prevents a common problem: a specimen is manufactured, only for the team to discover immediately before testing that it does not adequately represent the target product for the requirement being evaluated.
How Is DVP&R Related to Prototypes?
In DVP&R, or Design Verification Plan and Report, every Verification result should be traceable to the relevant requirement and supporting evidence. Specimen configuration is an important part of this traceability.
If a requirement was verified using Prototype Revision B and the design was subsequently changed to Revision C, it must be determined whether the previous evidence remains valid. Without specimen traceability, a requirement may incorrectly remain marked as completed.
For this reason, prototype management, configuration management, and DVP&R are closely connected in practice.
Should Testing Be Repeated After a Prototype Changes?
There is no universal answer. An Impact Analysis should be performed to determine whether the change affects the requirement and the previous evidence.
If geometry relevant to the test has changed, the material has been replaced, or the evaluated software functionality has been modified, additional Verification may be necessary. Conversely, a change unrelated to the requirement does not automatically require retesting.
The article “Which Tests Should Be Repeated After a Design Change?” discusses this process in greater detail.
What Information Is Required Before Sending a Prototype to a Laboratory?
The test objective must first be defined, whether it is product development, Pre-Testing, DV, PV, or another process. The specimen configuration should then be documented at the required level of detail.
Part Number, design revision, material, manufacturing process, software version, and other characteristics affecting the test may need to be provided. Known differences between the prototype and the target design should also be identified.
This information helps ensure that the test result is not interpreted beyond the actual limitations of the specimen.
Must a Prototype Be Complete?
No. A specimen must be sufficient and suitable for the specific requirement. If the test concerns only a component, a complete vehicle may not be necessary. Conversely, if interaction with the vehicle structure or another subsystem is an important part of the requirement, testing the component alone may not be sufficient.
This decision should be based on the test method and applicable requirement. A more complete specimen is not necessarily better; it must be appropriate for the engineering question.
When Is a Prototype Unsuitable for a Test?
When differences between the specimen and the target configuration significantly affect the requirement being evaluated, the extent to which the result can be used to draw conclusions about the target design becomes limited.
This does not mean that the specimen is useless. The same prototype may still be highly valuable for product development, failure investigation, or comparative testing.
Therefore, asking “Can this Prototype be tested?” is usually not precise enough. A better question is: “Which engineering questions can this Prototype help answer?”
How Should Expensive Prototypes Be Managed for Testing?
The cost of a prototype is not limited to the price of its components and hardware. Engineering time, measurement equipment, fixtures, transportation, and the opportunity to use the specimen also have value.
For this reason, specimen allocation should be integrated into test planning. Non-damaging tests may be performed before damaging tests when their conditions are compatible, and certain specimens may be reserved for failure analysis.
However, the test sequence should be determined by the actual effect of each activity on the specimen rather than by a simple general rule.
A Suitable Prototype Does Not Necessarily Look Like the Final Product
A specimen's appearance is not a reliable indicator of its maturity. A prototype may look identical to a production vehicle while containing temporary software or internal components. Conversely, a specimen with an unfinished appearance may fully represent the target product for a specific structural requirement.
Therefore, rather than judging a specimen by its appearance or development stage designation, the characteristics affecting the test should be evaluated.
This approach transforms prototype management from a purely logistical activity into an integral part of product Verification planning.
A Prototype Is a Learning Tool, Not Merely an Incomplete Version of the Final Product
A prototype creates real value when it is built and used to answer a specific engineering question. A Concept Prototype can help evaluate geometry, a Development Mule can enable early development of a system, an Engineering Prototype can reveal failure modes, and a specimen closer to production can provide stronger evidence about the target product.
However, none of these designations alone determines the validity of the results. It is necessary to understand which specimen characteristics represent the target design, which elements remain temporary, and which characteristics affect the requirement being evaluated.
Therefore, before every test, instead of simply asking “Is this specimen a Prototype or Production-intent?”, a more precise question should be considered: “For the requirement being evaluated, do the relevant characteristics of this specimen adequately represent the target configuration?” The answer determines how reliably the test result can support the project's next decision.