Introduction

0.1 General

Electronic tolling systems are complex distributed systems involving critical technology such as dedicated short-range communication (DSRC), camera-based technology (e.g. automatic number plate recognition, ANPR) and global navigation satellite systems (GNSS). These technologies are all subject to a certain behaviour that can affect the computation of the charges. Thus, to protect the interests of the different stakeholders involved, particularly toll service users (SUs) and toll chargers (TCs), it is essential to define metrics that measure the performance of the system in terms of computation of charges, and that ensure that the potential resulting errors are acceptable. These metrics will be a useful tool for establishing requirements for the systems and for examining the system capabilities during acceptance and throughout the operational life of the system.

In addition, to ensure the interoperability of different systems, it is necessary to agree on common metrics for use and on the actual values that define the required acceptable performances. However, these points are not covered in this document.

Instead, this document is defined as a toolbox standard of examination tests, with a method for defining and documenting a specific examination framework to meet specific needs. The detailed choice of the set of examination tests within an examination framework depends on the application and the respective context. Conformance to this document means using the definitions and prescriptions laid out in this document whenever the respective system aspects are subjected to performance measurements, rather than using other definitions and examination methods.

0.2 Charging performance metrics

This document also defines a set of charging performance metrics with definitions, principles and formulae, which together make up a reference framework for the establishment of requirements for electronic fee collection (EFC) systems and their later examination of the charging performance.

These charging performance metrics are intended for use with any toll scheme, regardless of its technical underpinnings, system architecture, tariff structure, geographical coverage or organizational model. They are defined to treat technical details that can differ between technologies as a “black box”. They focus solely on the outcome of the charging process, i.e. the amount charged in relation to a pre-measured 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 (FE) interface and the interoperability interfaces between toll service providers (TSPs) and TCs, as well as information on the end-to-end level.

Metrics for the following information exchanges are defined:

— charge reports (including usage evidence);
— toll declarations;
— billing details and associated event data;
— payment claims on the level of user accounts;
— exception lists;
— end-to-end metrics which assess the overall performance of the charging process.

The proposed metrics are specifically addressed to protect the interests of the actors in a toll system, such as TSPs, TCs and SUs. They can be used to define requirements (e.g. for requests for proposals) and for performance assessments.

Toll schemes take on various forms as identified in ISO 17573‑1 and ISO 12855. In order to create a uniform performance metric specification, toll schemes are grouped into two classes based on the character of their primary charging variable:

— charging based on discrete events (charges associated to the fact that a vehicle is crossing or standing within a certain zone);
— charging based on a continuous measurement (duration or distance).

The following are examples of discrete (event-based) toll schemes.

— Single object charging: a road section, bypass, bridge, tunnel, mountain pass or even a ferry, charged per passage.

EXAMPLE 1

Most tolled bridges belong to this category.
— Closed road charging: a fixed amount is charged for a certain combination of entry and exit on a motorway or other closed road network.

EXAMPLE 2

Many of the motorways in Southern Europe belong to this category.
— Discrete road links charging: determined by use of specified road links, whether or not they are used in their entirety.

EXAMPLE 3

Heavy goods vehicle (HGV) charge in Germany.
— Charging for cordon crossing: triggered by passing in or out through a cordon that encircles a city core, for example.

EXAMPLE 4

Congestion and infrastructure charging schemes in Stockholm and Gothenburg (Sweden).

The following are examples of continuous toll schemes.

— Charging based on direct distance measurement: defined as an amount per km driven.

EXAMPLE 5

HGV charge in Switzerland and US basic vehicle miles-travelled toll systems concepts.
— Charging based on direct distance measurement in different tariff zones or road types: defined as an amount per km driven, with different tariffs applying in different zones or on different road types. This is a widely discussed approach, also known as time-distance-place charging, and is under consideration in European countries.

EXAMPLE 6

OReGO, the pilot programme in Oregon, North America.
— Time in use charge: determined by the accumulated time a vehicle has been in operation, or alternatively, by the time the vehicle has been present inside a predefined zone.

In all of these toll schemes, tolls can additionally vary as a function of vehicle class characteristics (such as trailer presence, number of axles, taxation class and operating function) and depending on time of day or day of week, such that, for example, tariffs are higher in rush hour and lower on weekends.

With this degree of complexity, it is not surprising to find that the attempts to evaluate and compare technical solutions for SU charging have been made on an individual basis each time a procurement or study is initiated, and with only limited ability to reuse prior comparisons made by other testing entities.

The identification of different types of schemes as proposed in the ISO 17575 series and their grouping in the mentioned two classes is described in Table 1. Table 1 also identifies the examples mentioned above.

Table 1 — Toll scheme designs grouped according to scheme categories

Examples	Scheme type	ISO 17575 series category
Single object charging	Discrete	Sectioned roads pricing
Closed road charging	Discrete	Sectioned roads pricing
Discrete road links charging	Discrete	Sectioned roads pricing
Charging for cordon crossing	Discrete	Cordon pricing
Time in use charge	Continuous	Area pricing — time
Cumulative distance charge	Continuous	Area pricing — distance
Charging for cumulative distance in different zones (or by road type)	Continuous	Area pricing — distance

0.3 Examination framework

The examination framework that is defined in this document is designed for measuring the metrics defined in Clause 6. The general aim is to achieve a maximum comparability and reproducibility of the results without restricting the technological choices in system design. Specific examination frameworks can be defined for the evaluation and monitoring phases of a project due to the differences in the availability of equipped vehicles.

a) Evaluation phase

The evaluation phase encompasses system evaluation and selection, as well as commissioning and ramp-up during implementation. Important aspects of this phase are:

— relatively small sample sizes; and
— well-controlled behaviour of test vehicles.
b) Monitoring phase

After the system has gone into operation, its behaviour needs to be monitored for several reasons, such as fine-tuning of the system performance, monitoring of service level agreements (SLAs) between contractual partners (supplier, TC, TSP, etc.). In this phase, the following system aspects can be expected:

— very large sample sizes possible, but with unknown behaviour of the vehicles;
— in principle all measurements from implementation phase possible, too.

0.4 Reader's guide

To understand the content of this document, the reader should be aware of the methodology and assumptions used to develop the examination framework; therefore, a suggested reading order is given below.

a) Annex B provides details of the underlying considerations for developing the examination framework.
b) Annex C provides background statistical information which will enable the reader to determine sample sizes and confidence limits based on the defined performance requirements.
c) Clause 5 provides the definition of the examination framework for the evaluation of charging performance.
d) Clause 6 provides definitions of charging metrics and their applicability to the scheme types described above.
e) Clause 7 contains the toolbox of examination tests for the evaluation of charging performance for the identified scheme types.
f) Annex A contains an example template for the documentation of examination tests and their results.
g) Annex D contains methods which can be used to reduce the required sample sizes for metrics with high and low probabilities during the evaluation phase.
h) Annex E provides examples of specific examination frameworks which have been developed in accordance with the methodology in 5.2.

PD CEN ISO/TS 37444:2023

Electronic fee collection. Charging performance framework

Current, Under Review

Published:

31 Jul 2023