What is the ERL scale and how does it guide solution transfer?

The ERL scale, Evidence Readiness Level, is the methodological framework developed by yeshcube to assess the maturity of evidence associated with human-impact solutions. It organizes progress from an initial hypothesis to consolidated results that support decisions about where, for whom and under which conditions a solution may be applied.

The scale covers projects in areas such as health, education, accessibility, social care and human development. In these settings, technical operation is assessed alongside effectiveness, safety, usability, acceptance, accessibility and suitability for the intended environment.

The validation problem

A technology may operate correctly from a computing or engineering perspective while important questions remain about its effects on people.

An intervention may also produce favorable results under controlled conditions and encounter difficulties during implementation. Usability, accessibility, cultural acceptance, staff training and sustainability can alter results when it moves into another setting.

Technology Readiness Levels, or TRLs, describe the development of a technology from basic principles to operation in relevant environments. This framework is useful for assessing technical maturity.

People-facing solutions also require evidence about ethical risks, user experience, cultural suitability and the conditions needed to preserve results during transfer.

A framework for evidence maturity

The ERL scale documents what is known about a solution at each stage of development and which questions remain open.

The framework is based on three foundations:

• Scientific rigor, through defined hypotheses, appropriate methods, documented results and critical review.
• Ethical integrity, through protection of the dignity, autonomy, privacy and safety of participants and users.
• Responsible transfer, through identification of the conditions required to apply a solution outside its original environment.

Assessment progresses through levels. Each transition requires evidence suited to the stage reached and to the risks associated with the solution.

The six ERL levels

The scale comprises six levels, from ERL-0 to ERL-5. Progress occurs when the available evidence meets the criteria defined for the relevant transition.

ERL-0 Initial hypothesis

ERL-0 covers the initial formulation of the problem, hypothesis and purpose of the solution.

Activities may include reviewing existing knowledge, conceptual design, preliminary risk identification and definition of the human or social value to be studied.

Evidence at this stage may include a hypothesis record, theoretical rationale, initial risk map and description of the intended population or setting.

ERL-1 Proof of concept

ERL-1 introduces an initial empirical test of the proposition.

This stage may include prototypes, pilot materials, technical tests and early studies in controlled environments with limited samples. Its purpose is to examine the feasibility of the concept and collect initial metrics.

Evidence may include a preliminary protocol, prototyping records, initial findings and an early assessment of ethical and technical risks.

ERL-2 Controlled pilot

ERL-2 covers limited assessment of the solution in an applied setting.

The pilot uses a defined protocol, appropriate measures and procedures for safety and supervision. It also documents accessibility, user experience and implementation conditions.

Evidence may include the pilot protocol, applicable ethical approval, a results report and records covering safety, usability and participation.

ERL-3 Initial transfer

ERL-3 represents the threshold for initial transfer within the framework.

The solution must have sufficient evidence to define a specific application, intended population and conditions of use. Assessment covers effectiveness, safety, usability, acceptance, accessibility and applicable regulatory compliance.

Evidence may include an integrated validation report, independent review, a public record of results and a transfer plan with defined responsibilities and monitoring mechanisms.

ERL-4 Validated scaling

ERL-4 examines whether the solution maintains its results and safety conditions when applied in additional settings or with different populations.

This stage may include replication, multicentre studies, longitudinal follow-up, cultural adaptation and economic assessment. It also requires implementation protocols capable of reproducing the relevant conditions.

Evidence may include replication reports, external review, adaptation documentation and sustainability analysis.

ERL-5 Consolidated impact

ERL-5 covers solutions with accumulated evidence, continuous monitoring and stable integration into their settings of use.

This level may include population-level outcomes, independent evidence synthesis, monitoring systems, specialist training and inclusion in guidelines, standards or policy.

Evidence may include impact reports, cumulative reviews, sustainability indicators and documentation of continuous improvement.

Multi-metric assessment

An ERL level is determined through several complementary dimensions. The weight and requirements of each dimension depend on the type of solution, intended population and application setting.

Scientific evidence

This dimension examines study design, hypothesis definition, measurement suitability, sample size and composition, consistency of results and potential for replication.

Critical review should identify the actual scope of the findings and the questions that remain open.

Acceptance and user experience

This dimension studies perceived usefulness, comprehension, usability, satisfaction, adherence and continuity of use.

Methods may combine quantitative measures with interviews, observation and other qualitative techniques.

Technical feasibility

This dimension assesses stability, performance, interoperability, accessibility and the ability of the technology to operate in its intended environments.

It also covers maintenance, operational safety and responses to failure.

Ethical and regulatory compliance

This dimension reviews consent, privacy, data protection, supervision, proportionality of risk and applicable regulatory obligations.

Requirements vary according to purpose, population and the types of data involved.

Economic sustainability

This dimension examines development, implementation and maintenance costs, together with the resources required to sustain the solution over time.

It also studies whether the model can preserve the conditions associated with the observed results.

Social impact and equity

This dimension examines accessibility, inclusion of diverse populations, distribution of benefits and risks, and possible effects on vulnerable groups.

Assessment should identify who can access the solution, who may be excluded and which adaptations are required.

Gates and stop rules

Progression between levels includes control points known as gates. These controls allow the evidence to be reviewed before a new stage is authorized.

Gates may include:

• Independent scientific review.
• Ethical assessment.
• Risk-benefit analysis.
• Verification of multi-metric criteria.
• Accessibility and equity review.
• Confirmation of applicable regulatory compliance.

The scale also includes stop rules. These rules allow development to be paused, reformulated or restricted when relevant risks emerge.

They may be triggered by:

• Harm or unforeseen adverse effects.
• Ethical or regulatory non-compliance.
• Negative or inconsistent findings.
• Technical problems affecting safety.
• Implementation difficulties that alter validated conditions.

A pause forms part of the validation process. It allows hypotheses, design or scope of use to be reviewed before work continues.

Methodological transparency

Traceability makes it possible to understand how a study was designed, which changes were introduced, what results were obtained and how decisions were made.

Depending on the stage and research design, documentation may include:

• Preregistration of protocols and hypotheses.
• Description of variables and analysis methods.
• Records of methodological changes.
• Reporting of favorable, negative and inconclusive results.
• Sharing of anonymised data where ethically and legally appropriate.
• Identification of conflicts of interest and funding sources.

Transparency supports independent review and helps establish the proper scope of conclusions.

Relationship with other frameworks

The ERL scale can be used alongside established technical, scientific and regulatory frameworks.

TRLs describe technological maturity. ERL focuses on the maturity of the evidence required to apply a technology to people and human settings.

The choice of research standards depends on study design. Relevant frameworks may include CONSORT for randomized controlled trials, STROBE for observational studies, SPIRIT for trial protocols and TIDieR for intervention descriptions.

Compatibility means that these standards may be used as references within an ERL assessment. Each project must identify those that apply to its methodology and regulatory field.

Applications of the ERL scale

Applied research

The scale supports definition of the starting point, objectives for each stage and evidence required for progression.

It also assists with tracking a project over time and coordinating scientific, technical, ethical and transfer teams.

Product and service development

ERL assessment connects the functions of a solution with the claims that can be supported by evidence.

Teams can identify which uses are ready, which conditions must be preserved and which applications require further testing.

Transfer and implementation

The scale supports transfer plans with defined populations, settings, responsibilities, risks and monitoring mechanisms.

ERL-3 marks the beginning of this stage within the framework. Later levels examine replication, scaling and consolidation of impact.

Institutional communication

An ERL level provides a common reference for communicating the status of a solution.

Communication should include the scope of the level, the conditions assessed and the limitations of the available evidence.

Development and validation of the framework

The ERL scale is a methodology developed by yeshcube to organize its research and transfer processes.

Its evolution requires practical application, documentation, independent review and assessment with scientific teams, institutions and implementation organizations.

Potential adoption by third parties will depend on clear criteria, reproducible assessments and transparent governance processes.

Scope and limitations

An ERL level describes the evidence available for a specific solution, purpose, population and set of conditions.

The level may change when the product, protocol, population, setting or assessed claim changes. Evidence obtained in one environment requires review before it is applied elsewhere.

The scale does not replace legal requirements, regulatory authorizations, ethical review or the scientific standards of each discipline. It provides a structure for integrating and documenting those requirements throughout transfer.

The framework’s usefulness depends on precise criteria, the quality of assessments and transparent communication of results.

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