This part of ISO/TS 17444 defines metrics for the charging performance of electronic fee collection (EFC)
systems in terms of the level of errors associated with charging computation.
This part of ISO/TS 17444 is a toolbox standard of metrics. The detailed choice of metrics depends on the
application and the respective context.
This part of ISO/TS 17444 describes a set of metrics with appropriate definitions, principles and formulations,
which together make up a reference framework for the establishment of requirements for EFC systems and
their later examination of the charging performance.
The charging performance metrics defined in this part of ISO/TS 17444 are intended for use with any Charging
Scheme, regardless of its technical underpinnings, system architecture, tariff structure, geographical coverage,
or organizational model. They are defined to treat technical details that may be different among technologies
and vendors or vary over time as a "black box".
They focus solely on the outcome of the charging process - i.e. the amount charged in relation to a premeasured
or theoretically correct amount - rather than intermediate variables from various components as
sensors, such as positioning accuracy, signal range, or optical resolution. This approach ensures comparable
results for each metric in all relevant situations.
The metrics are designed to cover the information exchanged on the Front End interface and the interoperability
interfaces between Toll Service Providers, Toll Chargers and Road Users as well as on the End-to-End level.

Metrics on the following information exchanges are defined:
- Charge Reports;
- Toll Declarations;
- Billing Details and associated event data;
- Payment Claims on the level of user accounts;
- User Accounts;
- End-to-End metrics which assess the overall performance of the charging process.

The details on the rationale of this choice are described in 5.1.
The proposed metrics are specifically addressed to protect the interests of the actors in a toll system, such as
Toll Service Providers, Toll Chargers and Road Users. The metrics can be used to define requirements (e.g.
for requests for proposals) and for performance assessment.
This part of ISO/TS 17444 recognizes two types of situations where a performance assessment is necessary:
a) when an assessment is carried out during a limited time span, such as when formulating requirements and
assessing systems for acquisition purposes, conducting acceptance testing as part of the commissioning
process, or as part of a certification procedure. Any one of these types of assessment is referred to as
an evaluation;
b) when an assessment is needed as an ongoing supervision process, throughout the lifetime of a system, in
order to validate contracted service levels, to identify fraud or malfunction, or to support ongoing maintenance
and performance improvement processes. This type of assessment is referred to as monitoring.