ISO/TS 17444-1:2012
(Main)Electronic fee collection — Charging performance — Part 1: Metrics
Electronic fee collection — Charging performance — Part 1: Metrics
ISO/TS 17444-1:2012 defines metrics for the charging performance of electronic fee collection (EFC) systems in terms of the level of errors associated with charging computation. ISO/TS 17444-1:2012 is a toolbox standard of metrics. The detailed choice of metrics depends on the application and the respective context. ISO/TS 17444-1:2012 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.
Perception du télépéage — Performance d'imputation — Partie 1: Métrique
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TECHNICAL ISO/TS
SPECIFICATION 17444-1
First edition
2012-10-01
Electronic fee collection — Charging
performance —
Part 1:
Metrics
Perception du télépéage — Performance d’imputation —
Partie 1: Métrique
Reference number
©
ISO 2012
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ii © ISO 2012 – All rights reserved
Contents Page
Foreword .iv
Introduction . v
1 Scope . 1
2 Normative references . 2
3 Terms and definitions . 3
4 Abbreviated terms . 7
5 Definition of charging performance metrics . 7
5.1 General . 7
5.2 Metric Identification . 11
5.3 End-to-End metrics . 11
5.4 User Account Metrics .12
5.5 Payment Claim Metrics .13
5.6 Billing Details Metrics .13
5.7 Toll Declaration Metrics .15
5.8 Charge Report Metrics .18
Annex A (informative) Defining Performance Requirements .21
Bibliography .24
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
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Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
In other circumstances, particularly when there is an urgent market requirement for such documents, a technical
committee may decide to publish other types of document:
— an ISO Publicly Available Specification (ISO/PAS) represents an agreement between technical experts in
an ISO working group and is accepted for publication if it is approved by more than 50 % of the members
of the parent committee casting a vote;
— an ISO Technical Specification (ISO/TS) represents an agreement between the members of a technical
committee and is accepted for publication if it is approved by 2/3 of the members of the committee
casting a vote.
An ISO/PAS or ISO/TS is reviewed after three years in order to decide whether it will be confirmed for a further
three years, revised to become an International Standard, or withdrawn. If the ISO/PAS or ISO/TS is confirmed,
it is reviewed again after a further three years, at which time it must either be transformed into an International
Standard or be withdrawn.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO/TS 17444-1 was prepared by Technical Committee ISO/TC 204, Intelligent transport systems, and by
Technical Committee CEN/TC 278, Road transport and traffic telematics in collaboration.
ISO 17444 consists of the following parts, under the general title Electronic fee collection — Charging performance:
— Part 1: Metrics [Technical Specification]
1)
— Part 2: Examination framework
1) To be published.
iv © ISO 2012 – All rights reserved
Introduction
Electronic Tolling systems are complex distributed systems involving critical technology such as dedicated
short-range communication (DSRC) and global navigation satellite systems (GNSS) both subject to a certain
random behaviour that may affect the computation of the charges. Thus, in order to protect the interests of the
different involved stakeholders, in particular Service Users and Toll Chargers, it is essential to define metrics
that measure the performance of the system as far as computation of charges is concerned and ensure that
the potential resulting errors in terms of size and probability are acceptable. These metrics will be an essential
tool when establishing requirements for the systems and also for examination of the system capabilities both
during acceptance and during the operational life of the system.
In addition, in order to ensure the interoperability of different systems it will be necessary to agree on common
metrics to be used and on the actual values that define the required acceptable performances, although this is
not covered in this part of ISO/TS 17444.
Toll schemes take on various forms as identified in ISO/TS 17575 (all parts) and ISO 14906. 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 when a vehicle crosses or
stands within a certain zone), and those 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; 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; many of the motorways in Southern Europe belong to this category.
— Discrete road links charging: determined by usage of specified road links, whether or not used in their entirety.
EXAMPLE German heavy goods vehicle (HGV) charge.
— Charging for cordon crossing: triggered by passing in or out through a cordon that encircles a city
core, for example.
EXAMPLE Stockholm congestion charging.
The following are examples of continuous toll schemes.
— Charging based on direct distance measurement: defined as an amount per kilometre driven.
EXAMPLE Switzerland’s HGV charge; US basic vehicle miles travelled approach.
— Charging based on direct distance measurement in different tariff zones or road types: defined as an
amount per kilometre 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 many European countries. The pilot programme in Oregon is an example from 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 these examples of toll schemes, tolls may additionally vary as a function of vehicle class characteristics
such as trailer presence, number of axles, taxation class, operating function, and depending on time of day or
day of week, so that, for example, tariffs are higher in rush hour and lower on the weekends.
With this degree of complexity, it is not surprising to find that the attempts to evaluate and compare technical
solutions for Service User 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 ISO/TS 17575 (all parts) and their grouping in
the mentioned two classes is described in Table 1, which also identifies the examples mentioned above.
Table 1 — Tolling scheme designs grouped according to Scheme categories
Examples Scheme type ISO/TS 17575 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 (or time) in different zones Continuous Area pricing – distance
(or by road type)
No toll schemes are purely continuous. At the very least, a system must be able to stop accumulating charges
when it leaves a jurisdiction in which a charge is due, and resume charging when it returns or enters another.
Additionally, many Charging Schemes are set up so that the tariff is modified using discrete parameters, such
as spatial zones, time spans, vehicle classes, etc. Under those circumstances, each unit of distance or time
costs a different amount depending, for example, on whether it takes place inside or outside an area, such as
a city, whether a trip takes place in rush hour or at night, or depending on what type of vehicle is used. In this
part of ISO/TS 17444 references to a “continuous system” have to be understood as those systems having
some continuous behaviour even though they may also integrate some discrete nature. References to “discrete
systems” are limited to those systems that are purely discrete.
In these schemes, all the discrete parts (zones, cordons, events, time, vehicle class, etc.) that a system has
to identify are translated into a particular tariff (e.g. price per kilometre) that has to be applied to the measured
continuous variable (e.g. travelled kilometres) resulting in another continuous parameter, money.
Among the different Interoperability Application Profiles defined in CEN/TS 16331, only Section Road Tolling
has a purely discrete nature while the other four profiles have both discrete and continuous natures.
Some features of discrete and continuous toll schemes that are of relevance for the definition of metrics
proposed in this part of ISO/TS 17444 are analysed below.
Discrete toll schemes
In a discrete toll scheme, distinct events are associated with the identification of Charge Objects. It can be
that a vehicle crossed a cordon, passed a bridge, was present in an area, or in an area on a given day. An
event that takes place can either be correctly recorded by the system or can be missed. However, there is also
the possibility that an event is recorded even though it did not actually take place. This is summarized in the
following matrix in Table 2.
Table 2 — Theoretical event decision matrix for discrete schemes
System detects Chargeable Event
Event Matrix
Yes No
Missed Recognition
Correct
Yes
Charging
(Undercharging)
Chargeable Event takes
place
False Positive
Correct
No
Non-charging
(Overcharging)
In this matrix there are two successful scenarios (Correct Charging and Correct Non-charging), and two
unsuccessful (Missed Recognition and False Positive). The unsuccessful scenarios have very different
consequences. A Missed Recognition, i.e. a Chargeable Event that takes place but is not recorded by the
system, implies an undercharging, as the Service User is not charged.
vi © ISO 2012 – All rights reserved
In the case of False Positive, a vehicle that is not using the toll domain is being charged for an event which did
not take place. This implies an overcharging which is in violation of the legal rights of the Service User, and
ultimately risks eroding trust in the system.
This part of ISO/TS 17444 therefore makes a distinction between the two types of errors and defines associated
metrics to protect the interests of the Toll Charger and Service Users in terms of the allowed probabilities of
those events.
Continuous toll schemes
A continuous toll scheme is one where the charge is calculated using accumulated time or distance the base
tariff is applied to.
Note that a
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