ISO/TR 25221:2025
(Main)Electronic fee collection — Image-based tolling systems — Measurable characteristics
Electronic fee collection — Image-based tolling systems — Measurable characteristics
This document analyses the processes of image-based systems to be used for tolling purposes, with the aim to identify their specific characteristics, and where these characteristics can be observed. The study intends to answer the following questions: a) Which are the relevant characteristics of an image-based system used for electronic fee collection (EFC)? b) How can these characteristics be specified?
Perception de télépéage — Systèmes de péage basés sur l'analyse d'images — Caractéristiques mesurables
General Information
Standards Content (Sample)
Technical
Report
ISO/TR 25221
First edition
Electronic fee collection — Image-
2025-01
based tolling systems — Measurable
characteristics
Perception de télépéage — Systèmes de péage basés sur l'analyse
d'images — Caractéristiques mesurables
Reference number
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Symbols and abbreviated terms. 2
5 Framework and classifications of discrete tolling systems . 3
5.1 General — Dimensions of the problem .3
5.2 General to processes and functional variables .3
6 Variables in image-based tolling systems . 10
6.1 General .10
6.2 Detection rate .11
6.2.1 Definition .11
6.2.2 Detection of false positives rate .11
6.2.3 Detection of false negatives rate . 12
6.3 Identification rate . 12
6.3.1 Definition . 12
6.3.2 ANPR result verification .14
6.4 Classification rate .14
6.5 Association of identified licence plates with registered vehicles .16
6.6 V erification system added value and verification error .16
7 Testing and performance evaluation . 17
7.1 Generalities .17
7.2 Suitability of characteristic variables .17
Annex A (informative) Image-based systems in contexts different from EFC . 19
Bibliography .20
iii
Foreword
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iv
Introduction
[15]
The European Commission Implementing Regulation (EU) 2020/204 on detailed obligations of European
electronic toll service providers includes among the allowed tolling techniques: “electro-optical imaging
systems at the toll charger’s fixed or mobile equipment at the roadside, providing means for automatic
number plate recognition (ANPR), in EFC systems where the installation and use of an OBE is not required.”
ISO/TR 6026, produced by ISO/TC 204 in collaboration with CEN/TC278, identifies necessary areas of
standardization for image-based tolling. Activities to revise existing EFC standards to support ANPR
technologies have already been started.
It is well known that certified equipment is required, when ANPR is used for purposes other than tolling
(for example, limited traffic zones and speed limit enforcement), and that certification activity requires test
suites. This area has so far not been addressed in the field of EFC.
Also, while some phases in the process of electronic fee collection can be devised as technology independent,
at least the phases of recognition and the identification of vehicles are strictly dependent on the technology
used for tolling, so, in the specific case of ANPR, they depend on the ANPR technology.
Some regional standards (for example, UNI 10772) specify procedures for testing the optical and optical
character recognition (OCR) capabilities of ANPR systems, but the process chain of EFC is much wider than that.
A study is needed to identify characteristics of image-based systems for tolling to be tested for conformance
to specifications and to measure key performance indicators (KPIs).
It is recognized that image-based systems that are suitable for tolling can be used for other purposes.
Although such systems are out of the scope of the present document, informative Annex A is provided with
some examples and case studies.
v
Technical Report ISO/TR 25221:2025(en)
Electronic fee collection — Image-based tolling systems —
Measurable characteristics
1 Scope
This document analyses the processes of image-based systems to be used for tolling purposes, with the aim
to identify their specific characteristics, and where these characteristics can be observed. The study intends
to answer the following questions:
a) Which are the relevant characteristics of an image-based system used for electronic fee collection (EFC)?
b) How can these characteristics be specified?
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes
requirements of this document. For dated references, only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO/TS 17573-2, Electronic fee collection — System architecture for vehicle related tolling — Part 2: Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/TS 17573-2 and the following
terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
automated number plate recognition
ANPR
technology to automatically read vehicle registration plates
Note 1 to entry: A vehicle registration plate typically contains the indicator or the code of the country that issued the
vehicle registration plate.
Note 2 to entry: Optical character recognition techniques are typically part of the technology associated with
automated number plate recognition.
[SOURCE: ISO 17573-2:2020, 3.18]
3.2
enforcement
means to identify and pursue violators of laws, regulations or rules
3.3
false negative
incorrect reporting of a failure when in reality it is a pass
[SOURCE: ISO/IEC TR 29119-11:2020, 3.1.34]
3.4
false positive
incorrect reporting of a pass when in reality it is a failure
[SOURCE: ISO/IEC TR 29119-11:2020, 3.1.35]
3.5
formally valid licence plate
licence plate that has been correctly identified as for the nationality of the vehicle, the characters and the
numbers, and the associated format
3.6
free-flow tolling system
collection of tolls on toll roads without the use of physical toll barriers
3.7
constrained tolling system
collection of tolls on toll roads that impose restrictions (in road lanes or speeds, or both) on vehicles where
tolls are collected
Note 1 to entry: This covers, among others, all toll booths and toll plazas based tolling systems.
3.8
true negative
correct reporting of a failure when it is a failure
[SOURCE: ISO/IEC TR 29119-11:2020, 3.1.82]
3.9
true positive
correct reporting of a pass when it is a pass
[SOURCE: ISO/IEC TR 29119-11:2020, 3.1.83]
4 Symbols and abbreviated terms
A association rate
r
A number of correct ANPR results (true positives)
tp
C classification rate
r
C number of correctly classified vehicles (true or semi-true positives)
m
D number of detected false positives
fp
D number of detected false negatives
fn
D , detection of false negatives rate
nr
D detection of false positives rate
pr
D detection efficiency
r
Im ratio between the number of vehicles correctly identified by the secondary
secondary
system and the total number of correctly identified vehicles by the primary
and secondary systems
Ip is the number of vehicles correctly identified only by the secondary system
secondary
ID identification rate
r
P number of formally identified licence plates
f
P number of identified licence plates corresponding to existing real identified
r
vehicles, that combines the res
...
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