ARCHIVES OF TRANSPORT ISSN (print): 0866-9546

Volume 60, Issue 4, 2021 e-ISSN (online): 2300-8830

DOI: 10.5604/01.3001.0015.5503

ANALYSIS OF THE POSSIBILITY OF IMPLEMENTING

INTEROPERABILITY TESTS ON POLISH RAILWAYS

Przemysław ILCZUK1, Agnieszka ZACZEK2, Magdalena KYCKO3

1
Warsaw University of Technology, Faculty of Transport, Warsaw, Poland
2
Office of Rail Transport, Warsaw, Poland
3
Railway Institute, Warsaw, Poland

Abstract:
Ensuring the greatest possible interoperability of rail transport, especially for railways in Europe, is one of the key projects
to be implemented using the European Rail Traffic Management System (ERTMS), including the European Train Control
System (ETCS) and the Global System for Mobile Communications-Railways (GSM-R). The ERTMS system aims to replace
many different rail traffic control systems with one, common and unified European solution (Commission Regulation (EU)
2016/919, 2016), (Directive (EU) 2016/797, n.d.) Its creation was dictated by the desire to standardize the traffic control
systems present in the territories of various European countries, at the same time extending their functionality and elimi-
nating the existing technical barriers. The aim of this article is to present the possibility of implementation interoperability
tests - IOP tests, on Polish railways. These tests are intended to provide a faster, more accurate and less costly demonstra-
tion of compliance with the ETCS interoperability requirements compared to field tests. The work defines the concept of
interoperability tests as well as the purpose of their application. The general principles and procedures for conducting
interoperability tests are presented. In the further part of the work, the operation of laboratories in the European Union is
analysed. The laboratories functional in Switzerland and Spain were selected for this analysis. Following, the paper pre-
sents the validity of implementing interoperability tests on the territory of the Republic of Poland. On the basis of the pan-
European procedure of conducting interoperability tests and the experience of foreign independent laboratories, conditions
for the implementation of tests in the Polish railways were developed, which could be used in the future to introduce IOP
tests in Poland.
Keywords: IOP tests, interoperability, ETCS tests

To cite this article:

Ilczuk, P., Zaczek, A., Kycko, M., 2021. Analysis of the possibility of implementing
interoperability tests on Polish railways. Archives of Transport, 60(4), 71-86. DOI:
https://doi.org/10.5604/01.3001.0015.5503

Contact:
1) przemyslaw.ilczuk@pw.edu.pl [https://orcid.org/0000-0001-9317-8710]; 2) agnieszka.zaczek@utk.gov.pl
[https://orcid.org/0000-0002-7461-9995]; 3) mkycko@ikolej.pl [https://orcid.org/0000-0002-5630-2812]

Article is available in open access and licensed under a Creative Commons Attribution 4.0 International (CC BY 4.0)
72 Ilczuk, P., Zaczek, A., Kycko, M.
Archives of Transport, 60(4), 71-86, 2021

1. Introduction check the technical and functional compatibility of

The increasing development of railways in recent the ERTMS between rolling stock and the rail net-
years with the emergence of new traffic manage- work. They also provides a solution which reduce
ment systems such as European Rail Traffic Man- the effort required to put a new line into service and
agement System (ERTMS) means that both the rail- minimize the temporary decommissioning of infra-
way infrastructure and vehicles must be equipped structure and rolling stock (by replacing test drives
with European Train Control System (ETCS) and with simulation studies). Selected aspects of integra-
Global System for Mobile Communications-Rail- tion between ERTMS / ETCS on-board and track-
ways (GSM-R) (Commission Regulation (EU) side devices are presented in articles (Adamski et al.,
2016/919, 2016), (Pawlik, 2015), (Girardi et al., 2019) and (Karolak, 2021). Presented appliance can
n.d.). In some European countries, the GSM-R sys- be used to carry out tests before a physical imple-
tem is already being replaced by the LTE system for mentation of ERTMS on a new line as well as in ad-
traffic guidance (CHRZAN, 2021). While in Poland vance introduction of ERTMS equipped rolling
is predicted that by the end of 2030, 6549 km of lines stock on a specific trackside implementation.
will be equipped with ETCS. Vehicles running on The aim of this article is to present the process of
those lines, also have to be equipped with this sys- IOP tests and possibilities of implementation of IOP
tem accordingly to KPW (KPW, 2017) and author- tests in Poland. The additional aim of this article is
ized under data published by the Office of Railway to encourage representatives of legislative authori-
Transport, in Poland, out of 6 833 traction vehicles ties and authorities responsible for safety to use sim-
(as of 31 December 2019), only around 10 % are ulation methods in the process of authorization to
equipped with GSM-R radio. According to the Re- exploitation.
port (UTK, 2019), 215 traction units were equipped This article is dedicated to the use of IOP tests for
with ETCS at the end of 2018. Gathered numbers ETCS testing purposes to confirm the compatibility
show that it is necessary to intensify the process of of on-board equipment with the track-side imple-
equipping traction vehicles with ETCS and GSM-R. mented equipment. The article aims to show how
The process of running vehicle and placing it in ser- IOP tests are carried out in other countries and how
vice must also be triggered, following by safety re- such tests could be carried out in Poland. In addition,
quirements. One of the most important steps in plac- the article analyzes the requirements and solutions
ing in service the vehicles is to perform the appro- implemented in Europe in terms of standards and re-
priate checks according to the operational scenarios quirements in Poland. In the article, the analysis of
developed. However, operational scenarios are al- introducing IOP tests to Poland was studied. The
ready carried out on physical and implemented de- problem of organisation of IOP laboratory, assump-
vices. Bearing in mind the costs of production, pro- tions for conducting IOP tests as well as their organ-
gramming and maintenance of ERTMS devices, it is isation and realisation were discussed.
important that any irregularities and rules of interac- In the first chapters of this article, IOP tests were de-
tion of individual elements of the ultimately coher- fined and their implementation in different European
ent and compatible system are detected at the earliest countries was described. In the next part of the arti-
stage as possible. cle challenges connected with introduction of IOP
In order to achieve safe and reliable operation of the tests were described and scenarios of their imple-
ERTMS system, numerous tests of all devices in the mentation in Polish conditions were proposed. Then
system must be performed (EN 50129:2003, n.d., p. proposals for the organization of IOP laboratories,
2003). However, the high cost of infrastructure and roles and responsibilities in the process of their cre-
rolling stock makes it costly and time-consuming to ation and guidelines for their implementation are
put them out of normal use for testing and evalua- discussed.
tion. For this reason, the use of laboratory simula-
tions is even more than justified. Within the frame- 2. Literature review
work of railway simulations, we can find various IOP tests are conducted to verify the correct opera-
functions such as driving and operational simulators tion of the ETCS system. The technical description
and simulators for equipment testing and data anal- of the ETCS system is presented in the ETCS system
ysis. Interoperability tests (IOP) are designed to requirements specification, i.e. Subset-026 (ERA,
Ilczuk, P., Zaczek, A., Kycko, M. 73
Archives of Transport, 60(4), 71-86, 2021

2016a). This is an essential document allowing to ensuring interoperability and compatibility of

fully understand the functional aspects of ETCS sys- ERTMS within each country. For this reason labor-
tem. However, demonstration that ETCS equipment atories have different rules for: laboratory manage-
complies with the requirements of the TSI is pro- ment, recognition of tests in authorization process,
vided on the basis of: prerequisites for ERTMS subsystems, accepted op-
− Subset-076-5-2 - Functional test case specifica- erating scenarios, scope of the tests, or documents
tions (ERA, 2017b); confirming the performance of tests.
− Subset-076-6-3 - test sequence specifications One of the methods of conducting interoperability
(ERA, 2017c); tests is the use of serial communication channels, as
− Subset-076-7 - specification of the test scope described in the article (Hwang, 2015) in which it
(ERA, 2017a); was proposed a new interoperability test method and
which specifies the tests to be used to confirm the the tool to support it for the functional safety valida-
technical compatibility and functionality of the on- tion where the Ethernet and serial communication
board ETCS with the requirements of Subset-026 channels used by the actual train control systems are
(ERA, 2016a). in common use. Another approach to interoperabil-
It should be noted, that the ERTMS specifications ity tests is presented in the article (Barberio et al.,
give some leeway to the implementation of system 2014) where the results of research carried out under
functionality. Taking this into account, it is not the ARTEMIS CRYSTAL project, which tackles the
100% certainty that the on-board and track-side challenge to establish and push forward an Interop-
equipment is fully compatible with each other, even erability Specification (IOS) as an open European
if both fulfill the applicable specifications (ETCS standard for the development of safety-critical em-
System Management Switzerland, 2014). bedded systems. ETCS requirements and compati-
The approach to ETCS tests is described in the Eu- bility problems are dealt with in the document (Holst
ropean Union Agency for Railways guide (ERA, Moller, 2021), which presents test examples.
2017d), which presents the methodology in relation The ETCS laboratory testing approach is also pre-
to the subset requirements - 076, while this docu- sented in an article (Solas et al., 2016) which dis-
ment does not specify how interoperability tests cusses two novel laboratory tools that the EATS pro-
could be carried out in individual countries. In par- ject (FP7-TRANSPORT-314219) has produced in
ticular, the scope of tests may take into account na- order to overcome some of the problems those pro-
tional requirements that may go beyond the TSI cesses show and advance towards the “ Zero On-Site
(Commission Regulation (EU) 2016/919, 2016). Testing ”paradigm - a method that assumes no field
Union Industry of Signalling (UNISIG) developed testing, only laboratory testing. On the one hand,
dedicated specifications in 2012: saboteurs for the internal interfaces of the ETCS on-
− Subset-110 - IOP test guidelines (ERA, 2016c); board system have been created. These saboteurs in-
− Subset-111 - IOP test environment definition tegrate seamlessly with the rest of the elements of
(ERA, 2016d); the testing laboratory and allow to gather evidences
− Subset-112 - Basics for IOP Test Scenario Speci- regarding the safety functions of the equipment un-
fications (ERA, 2016b). der test. On the other hand, the Wireless Communi-
These specifications define the laboratory tests be- cation Emulators have been also developed. These
tween on-board system and the real conditions on tools allow to put the wireless interfaces of the
the infrastructure before physically implemented. ETCS on-board equipment in the worst cases it will
The first version of the mentioned above specifica- find in a real environment, by reproducing and in-
tions was officially signed by the members of the or- jecting noise and interferer signals, and measuring
ganization in 2014. The current version, as amended, the effect in the equipment under test. A similar ap-
is from 2016. proach was also presented in (Berbineau et al., 2021)
A review of laboratories offering IOP tests in Europe and (Nardone et al., 2020).
indicates that they already operate in Spain, Italy, While the authors of the article (Rosberg et al.,
Germany (Website, 2019), (Jaschke et al., 2005), 2021) indicate a number of problems identified in
Holland, Belgium, Denmark or Switzerland (Le relation to ERTMS. They also recommend the use
Borgne, 2019). The IOP tests are mainly aimed at of simulation methods to predict and solve them, as
74 Ilczuk, P., Zaczek, A., Kycko, M.
Archives of Transport, 60(4), 71-86, 2021

methods with significantly lower costs than field land it is the Federal Transport Office - FOT) to en-
tests, or to implement corrections after implementa- sure and enforce ETCS interoperability. The studies,
tion. recommendations and requirements defined by this
The application of the simulation approach is now entity must always be taken into account and applied
also more widely used, as it is also used for routing in the IOP tests.
trains (Di Meo et al., 2020) and (Gago & IOP tests are an important part of a broader concept
Siergiejczyk, 2020), as well as for testing geoloca- in Switzerland, adopted by SM ETCS CH. It is a
tion systems (Filip, 2020). safety concept for obtaining an ETCS system au-
An important aspect that is the subject of many cur- thorization (Le Borgne, 2019). It involves obtaining
rent publications is to propose formal methods for safety evidence for the track-side and on-board parts
correctness testing, currently in the implementation of ETCS by the suppliers at the various stages of im-
phase, ERTMS level 3 (Di Meo et al., 2020), plementation and for the integration of ETCS as a
(Dghaym et al., 2020), (Arcaini et al., 2020), (Mam- whole. The safety concept adopted ensures that any
mar et al., 2020), (Tueno Fotso et al., 2020) and in discrepancies in ETCS can be verified at a very early
the field of cybersecurity (Abourahim et al., 2020). stage of implementation.
However, none of the presented documents specifies In the context of tests to verify the technical func-
the exact requirements for interoperability tests, let tional compatibility between the On-board and
alone tests that could be used in Polish conditions. Track-side parts of ETCS (IOP tests), the interoper-
Each country has its own additional requirements, ability of the system as a whole is a difference due
systems or units that have the required conditions for to certain defects in the specifications dedicated to
interoperability testing. the different parts of the system. It should be stressed
In view of these differences in the conduct of the that according to SM ETCS CH, product faults that
IOP tests, the tests carried out in laboratories in should generally be identified during product tests
Switzerland and Spain will be presented. (verification of ETCS as an interoperability constit-
uent) are often only detected during IOP tests (ETCS
2.1. Interoperability tests – Switzerland System Management Switzerland, 2014)
Three laboratories conducting tests for four existing Figure 1 shows the participation of actors in IOP
ERTMS lines are currently in Switzerland. The la- tests in Switzerland.
boratory is owned by ETCS trackside suppliers Tha- From the below figure, cooperation between track-
les, Siemens and Alstom. IOP tests are carried out side and on-board ETCS suppliers in IOP tests can
on ETCS on-board (OBU) and track-side (RBC or be particularly stressed.
L1LS) equipment. In addition, there are 15 infra- In advance of the starting tests in a Swiss laboratory,
structure managers (IM) in Switzerland, which is assumptions for IOP tests are required, which in-
important for testing. Despite of so many IMs, test- clude in particular:
ing by suppliers of the track-side part of ETCS en- − information about the implemented TSI baseline
sures an adequate level of verification of the com- and version, national requirements as well as the
patibility of the whole ETCS. Consequently, in- list of 'change request' implemented;
teroperability tests are not conducted for specific − the version of the Subset-091 specification defin-
railway lines, but for all ETCS implementations ing the safety requirements for ETCS technical in-
throughout Switzerland. These tests lean on Subsets- teroperability in levels 1 and 2 (ERA, 2015);
110, -111 and -112 developed by UNISIG (ERA, − declaration of any deviations from the specifica-
2016c), (ERA, 2016d), (ERA, 2016b). tion and confirmation that these deviations do not
It should be stressed that tests in laboratories are a cause any failure of the trackside or on-board
mandatory part of the trackside subsystem authori- equipment;
zation in Switzerland and a part of the authorization − a declaration by the supplier of on-board equip-
process for railway vehicles. ment confirming compliance with the applicable
In addition, there is a dedicated ETCS System Man- TSI requirements (as interoperability constitu-
agement Switzerland unit (SM ETCS CH) estab- ents);
lished by the national safety authority (in Switzer-
Ilczuk, P., Zaczek, A., Kycko, M. 75
Archives of Transport, 60(4), 71-86, 2021

Train manufacturer
Infrastructure manager ETCS track side supplier OBU supplier Vehicle keeper
Railway Undertaker

OBU
Contract Contract
supplier A
Infrastructure-
Manager/ Supplier
-
- IOP testing
- IOP statement Test cases Request to get
Laboratory OBU
Contract the IOP
test supplier B

Operational
concept/
scenarios
OBU
Contract
Engineering supplier C
rules (ETCS
System- IOP
Leader) statement

Fig. 1. Structure of participation in IOP tests in Switzerland (source: own study based on (ETCS System
Management Switzerland, 2014))

− the operational aspects to be considered as a basis 2.2. Interoperability tests – Spain

for selecting the implemented functionality of the ETCS, in Spain, is supplied by: Alstom, Ansaldo,
equipment in consultation with the suppliers; Bombardier, Siemens and Thales, with Thales sup-
− certificates of track-side and on-board suppliers plying only trackside equipment. The Cedex In-
that define the status of ETCS equipment and the teroperability Laboratory is an independent labora-
implementation of specifications (versions of tory offering interoperability tests of on-board and
specifications); track-side ETCS in Spain. The scope of the labora-
− how to build and run test cases (requirements); tory's activities includes the certification of individ-
− guidelines for defining test results (test protocols); ual ETCS components as well as the verification of
− how to handle and conduct tests in case of discrep- compatibility between track-side and on-board sub-
ancies, deviations; systems. The tests that Cedex carries out are defined
− the scope of assessment of individual test results jointly by Adif (National Infrastructure Manager),
and the overall assessment for a given test. Renfe (National Railway Undertaking), Cedex and
The next step after the tests in the Swiss laboratories the Ministry of Public Works and Transport.
is to review the IOP certificate, which summarizes IOP tests offered by Cedex consist of a developed
all verifications of compatibility of on-board equip- complete catalogue of test cases (215 for ETCS level
ment with track-side implementations for which in- 1 and 260 for ETCS level 2 (Cambronero et al.,
teroperability must be demonstrated. The review 2011)). These test cases are designed to test the main
shall cover any discrepancies that require specific functionality of the whole system, focusing on its
non-technical fault handling, specifying additional normal operation. The scope of these tests includes:
operational rules, behavior and provisions that apply speed control and braking curves, level transitions,
to them. The IOP testing process itself is relatively mode changes, temporary speed restriction manage-
expensive. The costs of conducting tests include: ment (TSR), drive permission management, odome-
costs of developing assumptions for IOP tests, costs try, ATO and predefined speed, DMI operation, na-
of IT equipment delivered to the laboratory, adapta- tional values.
tion costs, including costs of test tools, transport, etc. There is a complete catalogue of test cases in Spain
for testing track-to-train compatibility. This cata-
logue is constantly evolving, being complemented,
76 Ilczuk, P., Zaczek, A., Kycko, M.
Archives of Transport, 60(4), 71-86, 2021

optimized and corrected with the experience gained Depending on the configuration, the scope of test
during testing. cases required for Cedex varies. For example, for the
The article (Iglesias et al., n.d.) presents the real de- first case indicated, all test cases have to be per-
ployment of ERTMS in all the new Spanish High formed, as this means that a completely new ETCS
Speed lines. The paper shows not only the high level system is being implemented for both on-board and
of interoperability reached in Spain, where almost trackside applications. An in-depth analysis of each
all the ECTS suppliers are present in both track and specific situation to be tested is carried out. Then, on
on-board subsystems, but also the near future chal- the basis of the analysis of the expert group, a set of
lenges that shall be overcome to continue a success- test cases applicable to a given configuration is se-
ful ETCS deployment. In addition, the article (Igle- lected, based on the characteristics of the rolling
sias et al., n.d.) presents the conditions of laboratory stock and the line and taking into account the func-
tests that are carried out by the Cedex laboratory tionality of the systems for the implementation. The
(Fig. 2). tests are performed when the ETCS system is fully
Cedex offers five different test arrangement for operational, i.e. independent EC verification pro-
ETCS implementation (Cambronero et al., 2011): cesses have been completed.
− new line and new rolling stock; It should be stressed that the process of verifying the
− validated line and new rolling stock; functionality of the ETCS system does not end with
− new line and validated rolling stock; testing itself. The tests require further analysis,
− validated line and validated rolling stock on an- which is mainly based on observation of the driver's
other line; cab data during the tests, track-side data recorded by
− validated line and new rolling stock with software the on-board equipment and information provided
validated in another rolling stock. by the track-side and on-board ETCS suppliers. This
is an important stage during which both, the system
and functionalities are analysed in detail. A report on
the verification of compatibility is then issued and
assessed in order to obtain the placing in service of
the rolling stock or line.
In the authorization process, in Spain, IOP tests are
required by the relevant national legislation which
sets out the test requirements for checking technical
compatibility and safe integration. The tests are car-
ried out after on-board equipment certification pro-
cess and the relevant EC certificate of verification
gained. Some of the infrastructure integration tests
are carried out in the CEDEX laboratory, others are
carried out on the line. Costs related to the tests are
borne by the applicant (ETCS supplier).
Interoperability tests are being standardized by the sig-
naling companies grouped in UNISIG to detect early
problems in the integration of trackside (RBC-IXL and
Eurobalise) and Onboard equipment (EVC) from differ-
ent (or same) suppliers and to assure interoperability. The
test architecture is defined in the Subset111 and the sce-
narios are specified in the Subset-112.
According to UNISIG the purpose of the standardization
is to make IOP tests measurable and comparable, that
means giving customers and organizations (especially
National Safety Authorities, ERA and Notified Bodies) a
clear view on the status and results of IOP test. So they
Fig. 2. Traffic simulation Lab (CEDEX, 2019)
Ilczuk, P., Zaczek, A., Kycko, M. 77
Archives of Transport, 60(4), 71-86, 2021

can be compared and mutually recognized by different The one of the challenges for the near future are the
laboratories and different suppliers. implementation of the complementary tests in labor-
The IOP tests between different suppliers allow for early atory instead of on a real track. Although it has been
detection of faults in the implementation of the ETCS mentioned in the previous paragraph the progress al-
system and the correction of any errors before its instal- ready reached, there are still some pending issues
lation. (Iglesias et al., n.d.). mainly related to the realisation of L2 tests in the la-
The tests developed in Spain could be a first approach to boratory. The lab updating is in progress but in this
be considered by the European Railway Agency. A kind case the connection of the RBC to the laboratory
of similar tests should be defined by ERA to assure cross simulated interlocking has to be done in a proprie-
acceptance among different NSAs (National Safety Au- tary solution with each company. This is due to the
thorities). The Spanish approach of defining complemen- fact that the interface between interlocking and RBC
tary test and later on executing this tests in a lab compli- is not defined in the ERTMS specifications, and
ant with Subset-094 should be considered by the ERA as therefore shall be defined bilaterally between the lab
a good one to be included in the TSI (Iglesias et al., and each company. This fact increases not only the
n.d.). time but also the cost of laboratory tests execution.
The European project INESS (Integrated European
3. Research problem Signalling System) will solve this issue but up to that
The research problem of this paper is the analysis of time it will not be a standard solution (Iglesias et al.,
requirements connected with IOP tests implementa- n.d.).
tion and the proposal of tests implementation taking Another challenge is the migration process form
into consideration legal and technical conditions on ETCS version 2.3.0d to version 3.6.0 mentioned in
European and national level. the TSI (Commission Regulation (EU) 2016/919,
Compliance of ETCS equipment with the require- 2016). There is no strategy that would enable an or-
ments specified directly in the TSIs is the responsi- derly process of changing both trains and tracks to
bility of the ETCS Providers and is a prerequisite for version 3.6.0. This process is quite complex if we
starting the relevant IOP tests. The main assump- want to reduce the impact in the commercial exploi-
tions for IOP tests are: tation. In this case the existence of both ETCS levels
− the boundaries for testing are defined by on-board will allow completing the process by means of tem-
ETCS and track-side interoperability constituents porarily exploiting the line in one of the levels. In
− the on-board system and the trackside equipment addition, it has not been established who is to bear
come from different suppliers or from different the relatively large costs related to migration.
product lines of one supplier;
− IOP tests are performed at interfaces which allow 3.1. General assumptions for interoperability
the user to control and observe the behavior of the tests
system; On the basis of the IOP test guide - Subset-110
− IOP tests are visualized at ETCS interfaces, e.g. (ERA, 2016c) developed by UNISIG, it is possible
human-machine interface, protocol interfaces. to visualize the process of conducting IOP tests, as
Figure 3 illustrates the scope of IOP tests for the in- shown in Figure 4, together with determining the re-
tegration of the on-board and track-side parts of sponsibility of entities participating in the tests.
ETCS presented by UNISIG. As the figure 4 shows, the following stages can be
It should be stressed that the guidelines for IOP tests distinguished within the IOP tests: preparation
alone should not refer to requirements set out in the phase, testing phase and results reporting phase.
TSI. The purpose of standardizing IOP tests is to The preparation phase consists of configuring the
make them measurable and comparable. This means test environment, i.e. defining a common set of data,
that it is possible to provide users and organizations ensuring equal test conditions for devices from dif-
with a clear picture of performed tests and to ensure ferent suppliers. Then, it is necessary to prepare the
their interoperability, thereby promoting compatibil- data of the developed project, which is an instruction
ity tests between different suppliers. on how to conduct IOP tests based on supplier im-
plementation paths.
78 Ilczuk, P., Zaczek, A., Kycko, M.
Archives of Transport, 60(4), 71-86, 2021

ETCS technical/ Oper

Product interoperability
Development Product Test proof Subsystem Integration System integration System IOP

Other subsystem System

Product test
ATS
ATS Integration Subsystem
test ATS Test ATS

GSM-R Product test

GSM-R Integration Subsystem
Test GSM-R Test GSM-R
Interoperability

Techn. IOP Test Track subsystem

LEU/Balises Product test LEU/
LEU/Balises
Balises (TSI Conf)
(TSI Conf)
Integration Subsystem
ILS Product Test ILS Test Track Test Track Train-Track
Techn. IOP Test
Operational
RBC (TSI Conf)
RBC Product Test RBC IOP
Train-Track (for manufacturer
Integration coming after track
in operation)
Operational IOP Test ETCS
(for manufacturer coming before track in operation)

Techn. IOP Train subsystem

OBU Product Test OBU
Test OBU
(TSI Conf)
Engine Product Test
Engine Integration Subsystem
Test Train Test Train
Nat ATP Product Test Nat
ATP

Time
Fig. 3. UNISIG IOP test range (Subset-110) (source: own study based on (ERA, 2016c))

Then IOP test description is created, which is a spec- all tested subsystems and successful passing of the
ification of the overall test strategy and list of test test environment control and its documentation.
scenarios related to the given project. In the next As part of the test execution phase, the implemented
step, documentation defining test assumptions, in- test cases are conducted according to a pre-defined
cluding test case results and test environment speci- schedule as well as test documentation and non-
fication, is developed. Then, it is necessary to define compliance reports. This information is the basis for
test scenarios that support the practical implementa- analyzing the test results and for monitoring any
tion of the test description and correlate them with problems
previously defined test cases. The list of IOP test The final phase of IOP testing is results analysis and
scenarios should be designed to include all specific reporting. Based on documented results of per-
test cases for a given project. Finally, the simulated formed tests, a detailed analysis is carried out to de-
environment is installed in accordance with the la- termine the correct operation of the system and the
boratory configuration assumptions. The test envi- identified non-conformities. At the end of this phase,
ronment is considered ready after initial checking of final test reports are issued.
Ilczuk, P., Zaczek, A., Kycko, M. 79
Archives of Transport, 60(4), 71-86, 2021

INTEROPERABILITY TEST PROCESS

IOP Guidelines
Pre-requisites Preparation Execution Reporting

Trackside

Operational Test Case and

Procedures Test Case scenario
Acceptance selection preparation (see
criteria note)
Execute test in Evaluate results
Lab NCR reporting
Ready for Test
operation TSI environment
conformity wayside
report approved
National safety
Execute test in Acceptance authority
Lab Integration Field criteria approval (Out of
IOP Test Report evaluation scope of IOP test
and tuning
process)
Ready for Test
operation TSI environment
conformity OBU approved
report

Wayside
OBU suppliers Customer
suppliers
responsibility responsibility
responsibility

Fig. 4. The IOP testing process according to UNISIG (Subset-110) (source: own study based on (ERA,
2016c))

3.2. Interoperability Test Environment should be taken to ensure easy maintenance, updat-
According to Subset-111 - the IOP testing environ- ing and modernization of this environment, but at
ment (ERA, 2016d), the test environment architec- the same time ensuring its constant universality.
ture should be as simple as possible to allow the im-
plementation and testing of various ETCS system 3.3. Interoperability test scenarios
devices, but at the same time ensure easy combina- When developing IOP test scenarios, consideration
tion of test environments supported by different on- should be given to defining the input data, its struc-
board equipment and track-side suppliers. In addi- ture and content, i.e. general prerequisites, execution
tion, it is important that the architecture allows the sequences and anticipated test results. In this area, it
connection of real ETCS system devices to the test is crucial to define the content of the scenarios and
environment, while ensuring the use of interfaces for to maximally simplify the understanding and evalu-
different suppliers. It should also be universal ation of test scenarios operating in various IOP test
enough to enable re-use of solutions already availa- environments. The format of the evaluation and the
ble from the previously performed tests. In addition, report should be harmonized to make it easier to un-
it should be possible to use additional, proprietary derstand between different sides of the tests, but also
applications of a given provider (e.g. login or remote to maintain a uniform approach to the different tests.
access to the user interface). Such requirements are set in the Subset-112 specifi-
Continuous monitoring of the scenario should be en- cation - principles of IOP test scenarios (ERA,
sured within the test environment. All data ex- 2016b).
changed between the test environment and ETCS Testing scenarios should contain all information
devices should be recorded on an ongoing basis. It necessary to identify test itself and track changes, or
should also be emphasized that the test environment clearly defined restrictions on its use. They should
should in no way refer to a specific version of the provide the best understanding, comparability and
TSI CCS. As already mentioned, it is primarily to ability to easily maintain such IOP test scenario de-
allow flexible and universal use. Of course, care scriptions. Therefore, each test scenario should have
80 Ilczuk, P., Zaczek, A., Kycko, M.
Archives of Transport, 60(4), 71-86, 2021

in particular identification data, including change it is not possible to adopt 100% one solution and im-
histories; identified requirements, description and plement it. It is necessary to take into account a num-
presentation of the scenario; configuration of the test ber of important factors, such as the condition of the
environment for a given scenario; test prerequisites; Polish railway network and rolling stock equipment
execution sequences; expected results (verification with the ETCS system, organizational capabilities of
steps) with a range of acceptable deviations; final the infrastructure manager, or even KPW (KPW,
conditions determining the status of on-board equip- 2017), which will affect the shape of the laboratory
ment and the condition of the infrastructure. in Poland. This chapter presents the conditions for
The principles of IOP test scenarios developed by the implementation of IOP tests in Polish railway
UNISIG Subset-112 (ERA, 2016b) also define the conditions based on the analysis of existing labora-
parameters to be determined for the trackside and tories conducting IOP tests.
on-board ETCS layers for the purposes of conduct-
ing interoperability test scenarios. In addition, two 4.2. IOP testing laboratory
forms were also developed under this specification: In order to enable IOP tests, an independent labora-
the interoperability test scenario form and the IOP tory should be created that will be available to all
test report form. It is extremely helpful material for test applicants on an equal basis. The laboratory
creating rules for the implementation of the labora- should be properly accredited to conduct IOP tests.
tory offering this type of test. In this regard, it is possible to use the procedures and
experience of a laboratory operating in Spain which
4. Results has such accreditation.
4.1. Conditions for testing implementation in the The IOP test laboratory should be understood as a
Polish railways set of dedicated tools, ICT devices, test procedures
Considering the pace of ERTMS system develop- and competent personnel allowing to perform multi-
ment and implementation plans, there is a need to ple tests of ERTMS devices in a simulation environ-
implement interoperability tests in the Polish rail- ment. The laboratory should be organized in such a
way system. The described IOP test laboratories dif- way as to ensure the greatest possible flexibility of
fer in both organization and scope of tests. Each of use. First of all, through the possibility of using real
them has been adapted by individual countries to na- ETCS devices as well as through their simulation in
tional conditions. In the conditions of the Polish rail- a test environment. The test environment architec-
way market, which significantly differs from the ture should meet the requirements of Subset-111
ones analyzed (mainly due to national law, operating (ERA, 2016d), developed by UNISIG. Figure 5
regulations and differences in railroad technology), shows the architecture of such a laboratory.

User Interface

RBC Adapter RBC under Test

RBS

Test Control and Logging

OBU Adapter OBU under Test

RBS

Position of generic interfaces Test control link

Proprietary interfaces Communication link

Fig. 5. Architecture of the test environment according to UNISIG (source: own study based on (ERA,
2016d))
Ilczuk, P., Zaczek, A., Kycko, M. 81
Archives of Transport, 60(4), 71-86, 2021

The laboratory should be equipped with an adequate tax or checksum of telegrams generated by interop-
number of stands where IOP tests can be conducted. erability constituents. Both the on-board and track-
Each laboratory stand should be equipped with ap- side parts of the ETCS system for which IOP tests
propriate IT tools, connections and designated as- are to be carried out must be strictly in accordance
sembly points for real ETCS system devices. IOP with the requirements of the CCS TSI (on generic
test benches should be located in such a way that the level), which must be confirmed by the EC verifica-
test equipment is not affected by any external inter- tion certificate issued by a notified body with com-
ference that could falsify test results. Each work- petence in certification in this area.
station should also meet the relevant ergonomics re- Tests may be carried out at the level of the interop-
quirements, including handling of manipulators in erability constituents or subsystems. Testing should
the case of e.g. use as part of actual DMI display not be made dependent on a fixed configuration for
testing. a particular vehicle. However, to determine the full
It is also crucial to ensure that all tests for specific compatibility of the devices in the target conditions
devices are carried out in one test stand without the it is required. From the specific configuration and
need to change the configuration of devices during working environment on the vehicle of the ETCS
the entire procedure. Access control should also be system there are certain dependencies of operation,
provided for each test stand, thanks to which only such as braking curves, which depend on the per-
the person responsible for conducting IOP tests on centage of braking mass, determined by the manu-
given devices will be able to access during the test facturer of the railway vehicle. Here, the key is
procedure. The IOP testing laboratory should pro- whether IOP tests are to demonstrate ESC compati-
vide a high level of test automation. bility

4.3. Preliminary assumptions for IOP tests 4.4. Legal conditions

To conduct IOP tests, an IOP test manager should be In order to ensure the effectiveness of the implemen-
designated - the person responsible for conducting tation and conducting of IOP tests, they must be in-
IOP tests for a given project, who should be sup- troduced as mandatory in the process of applying for
ported by: infrastructure manager (e.g. by verifying an authorization for placing in service (placing on
and creating new test scenarios, sharing design data the market) for a type of railway vehicle what should
of each implementation), ETCS trackside and be included in the act on rail transport (UoTK, Dz.
onboard part suppliers and rolling stock manufac- U. 2003 Nr 86 poz. 789 as amended, n.d.) and the
turer (e.g. by providing test items and commission- interoperability regulation (Regulation 1042 of
ing IOP tests). 9.06.2021, n.d.). These tests give the opportunity to
IOP tests should be based on operational scenarios increase the coordination of suppliers and customers
and individual trackside implementations - in this of the ETCS system, as well as easier comparison of
area it is also necessary to base and use guidelines to the quality of systems from different manufacturers,
confirm ETCS System Compatibility (ESC), which and above all they can be used to demonstrate ESC
is to be defined by the infrastructure manager. Tests compatibility. Another argument for including IOP
should be carried out on devices representing rele- tests as required in the authorization process is the
vant parts of actual track-side deployments. Only need to perform ESC tests and enter the ESC com-
tests that cannot be performed in a laboratory envi- pliance parameters in the European Register of Au-
ronment should be carried out in real conditions - on thorized Types of Vehicles (ERATV) (Commission
the network, which is decided by the infrastructure Regulation (EU) 2016/919, 2016). Therefore, most
manager in consultation with the other parties par- tests should be carried out in laboratory conditions
ticipating in the tests taking into account the risks of in order to reduce the costs of test implementation,
not carrying out field tests. which is also allowed by (ERA, 2021) and (PKP
It should be emphasized that IOP tests (carried out PLK S.A., 2021b), (PKP PLK S.A., 2021a).
during the subsystem implementation phase) are not
intended for testing the generic compliance of a
product with the TSI, i.e. EC verification of the syn-
82 Ilczuk, P., Zaczek, A., Kycko, M.
Archives of Transport, 60(4), 71-86, 2021

4.5. Roles and responsibilities in IOP tests stand with testing equipment in a laboratory envi-
Infrastructure Manager ronment and with interfaces that meet the technical
An infrastructure manager should participate in the requirements contained in Subset-111.
organization of the laboratory. This is crucial be-
cause the infrastructure manager has all the data nec- IOP test manager
essary for conducting IOP tests regarding individual It is the IOP test coordinator who is responsible dur-
implementations of the ETCS system on the network ing the test for ensuring trouble-free running of the
it manages. As already mentioned, the infrastructure given IOP test from the point of view of technical
manager determines the ESC types for ETCS imple- settings of devices, simulation and reporting of re-
mentations on the infrastructure it manages. It is im- sults. It must also ensure the maintenance and nec-
portant that the manager must also guide engineer- essary updating of IOP testing tools. The coordina-
ing principles on his infrastructure in order to main- tor must have extensive knowledge of the design and
tain technical uniformity of trackside solutions. This programming of the ETCS system.
is crucial to ensure an adequate level of stability for
certain types of ESCs that on-board equipment man- Notified Body
ufacturers and railway vehicle manufacturers must The notified body is responsible for verifying that
meet. the technical compliance checks have been carried
With regard to conducting IOP tests, the manager out in accordance with the technical document pub-
should provide all implementation data to map ref- lished by the Agency. Based on the IOP test report,
erence conditions for individual ESC types. Works and if required, the ESC test report, the Notified
with the IOP test manager and provides all necessary Body shall confirm that the report has considered all
information to maintain test devices in accordance complete tests and has identified all non-conformi-
with specific ESC types and modifications. It should ties and limitations (if applicable). At this stage, the
be emphasized that it should be the infrastructure notified body no longer verifies in any way the in-
manager's responsibility to develop and / or verify teroperability constituents and their groups for
the IOP test list for testing, taking into account the which an EC declaration of conformity was issued
reference conditions for specific track-side imple- before IOP tests.
mentations.
4.6. Conducting IOP tests
Entity applying for IOP tests Conducting IOP tests should be in accordance with
The following entities may apply as an entity apply- the guidelines set out in Subset-110, -111, -112
ing for IOP tests: supplier of on-board ETCS system (ERA, 2016c), (ERA, 2016d), (ERA, 2016b). IOP
equipment, railway vehicle manufacturer, infra- tests should focus on network-specific (given ETCS
structure manager, railway vehicle owner or mod- deployment on the network) interface problems, in-
ernization contractor. The catalog of entities pre- cluding existing transitions. In particular, tests
sented corresponds to the ESC assumptions. In the should cover all relevant operating procedures,
process of obtaining authorization for placing on the mainly in degraded conditions (e.g., failures, de-
market of a railway vehicle type, the applicant for fects).
authorization is responsible for conducting ETCS Operation of the ETCS system is based on the con-
compatibility verification (ESC) for a given area of stant calculation and control of braking curves, that
use of the vehicle. is, calculating of the maximum allowable speed as a
The entity applying for the IOP tests must provide function of the road, constantly monitoring it and en-
certified equipment and software of the on-board suring a safe system response in the event of exceed-
part of the ETCS system and specify a representative ing (Gruba et al., 2018). The scope of IOP testing
configuration for the given IOP test together with the should include:
ESC types for which it applies for confirmation of − speed control (in individual driving modes)
compliance, in accordance with the conditions spec- − braking curves;
ified in the IOP testing process. It equips the test − transition between ETCS levels on the railway;
− entry / exit to / from the area equipped with the
ETCS system depending on the given level of
Ilczuk, P., Zaczek, A., Kycko, M. 83
Archives of Transport, 60(4), 71-86, 2021

ETCS and baseline implemented on the vehicle full driving supervision mode in the ETCS area of
and on the infrastructure; the given level and baseline;
− driving in individual modes and changing the driv- − Display of appropriate messages by the DMI in
ing mode; given circumstances, including the information
− establishing connection and maintaining commu- displayed at the driver's request, but also the order
nication with RBC by the on-board equipment; in which the messages are displayed;
− management of temporary speed limits (TSR); − Entering the ETCS area (appropriate level) with-
− monitoring of driving authorization data, includ- out confirmation by the driver;
ing testing the system's response to an unexpected − Operation of ETCS on-board equipment after re-
shortening or extension of a driving authorization; ceiving information about electroless areas or with
− track conditions (e.g. checking the system re- driving without stopping areas.
sponse to REC message, checking operation in the Above are only examples of test cases to demon-
event of loss of balis group, checking system be- strate ETCS system compatibility, including ESC
havior in the absence of STM / SHP mode); checks. Undoubtedly, it is also fully justified to use
− DMI work, including testing the proper display of an independent laboratory for the purpose of verify-
all messages required by the ETCS system in real ing the operation of the new trackside ETCS system
time; before its physical implementation on the railway.
− implementation of national variables.
The examples listed above are, of course, not a cat- 5. Conclusions
alog of closed verification that can and should be The ERTMS system is already a well-known, effi-
carried out as part of IOP tests - they are only a gen- cient technology used all over the world. However,
eral outline. Each determination of test cases should there is still a lack of flexibility in the area of author-
first of all be analyzed in detail by the infrastructure ization and certification. The key to the system's suc-
manager in consultation with the suppliers of the cess in the future is both cost reduction and simpli-
ETCS system in relation to the specific implementa- fication of system verification and authorization pro-
tion on the line and traffic conditions on this line, cedures. This applies to the implementation of a new
taking into account the required ESC checks. subsystem, and even more so to new versions of
Each item listed above should be approached in de- software related to already functioning subsystems.
tail and its correlations and relationships with the Currently, the process of placing ETCS equipment
others should be analyzed. Specific test cases should and subsystems in service requires a large number of
be precisely determined for individual ETCS system tests due to the complexity of signaling systems and
functions and possible traffic situations, their con- various engineering principles. Shift2Rail
nections in various configurations, but also in the ab- (Shift2Rail – European Railway Program for Inno-
sence of complete data or in the event of equipment vation of Railway Products) multi-year action plan
failure. As the example of the Spanish Cedex labor- states that the expenditure and time spent on testing
atory shows, 260 level test cases implemented dur- on the web is at least 30% for each specific project
ing IOP tests were developed for ETCS level 2. (Molina et al., 2018).
Examples of test cases implemented in the labora- This article demonstrates the relationship between
tory as part of IOP tests may be: ESC compatibility and IOP tests that should be con-
− Entry to the ETCS area of the given level and base- sidered as the only valid form of demonstrating ESC
line - on-board equipment in level 0 or STM / compatibility, as well as interoperability to which
SHP; IOP tests will contribute.
− Stopping the vehicle before the end of the driving Assuming that the developed simulated IOP testing
authorization in full supervision mode when driv- environment fully complies with the ETCS system
ing in the ETCS area of the given level and base- specifications and CENELEC specifications, as well
line; as exactly the same interfaces embedded in the ac-
tual equipment have been integrated in the labora-
− Speed control in full supervision mode while driv-
ing in the ETCS area of the given level and base- tory development process, it can be guaranteed that
the behavior of the simulated and actual system
line;
equipment is absolutely identical.
− Omission of the end of the driving authorization in
84 Ilczuk, P., Zaczek, A., Kycko, M.
Archives of Transport, 60(4), 71-86, 2021

It can be concluded that despite the considerable [2] Adamski, D., Białoń, A., & Łukasz, Z. (2019).
costs of developing this type of tool, the cost of track Selected aspects of proper integration between
tests is reduced, as the number of field tests is mini- ERTMS/ETCS on-board and trackside devices.
mized, which reduces the use of infrastructure and MATEC Web of Conferences, 294, 5008-.
rolling stock. What's more, laboratory tests allow https://doi.org/10.1051/matec-
you to perform multiple checks, which helps build conf/201929405008
confidence in the compatibility of implemented [3] Arcaini, P., Kofroň, J., & Ježek, P. (2020). Val-
parts of the system. idation of the Hybrid ERTMS/ETCS Level 3
The analysis carried out in this work has shown that using Spin. International Journal on Software
IOP tests are a tool that gives the opportunity to Tools for Technology Transfer, 22(3), 265–
prove ESC compatibility. In addition, IOP tests en- 279. https://doi.org/10.1007/s10009-019-
sure the interoperability of the ETCS system by var- 00539-x
ious ETCS suppliers on various system implementa- [4] Barberio, G., Di Martino, B., Mazzocca, N.,
tions and on different lines within the country with- Velardi, L., Amato, A., Gentile, U., Marrone,
out long and costly tests on rail lines. Tests in labor- S., Nardone, R., & Peron, A. (2014). An In-
atories can be carried out easier and faster than in the teroperable Testing Environment for
field, they do not require booking track closures, ERTMS/ETCS Control Systems. 8696, 147–
they do not affect the capacity on loaded lines. 156.
There is currently no laboratory in Poland offering [5] Berbineau, M., Sabra, A., Deniau, V., Gransart,
IOP testing to prove the compatibility of the ETCS C., Torrego, R., Arriola, A., Val, I., Soler, J.,
system, as it is implemented in other countries. Con- Yan, Y., Vizzarri, A., Mazzenga, F., Kharbech,
sidering the pace of ERTMS development, as well S., Clavier, L., Kassi, R., & Garcia-Loygorri, J.
as the advance of laboratories offer IOP tests, the re- M. (2021). Zero on site testing of railway wire-
lease of this type of tests in Poland should be given less systems: The Emulradio4Rail platforms.
priority, at least at a level equal to the implementa- 2021-April. https://doi.org/10.1109/VTC2021-
tion of the ERTMS system itself. Spring51267.2021.9448903
The article critically analyses the experience of other [6] Cambronero, M., Arranz, A., De LA Roza, C.,
countries that have already implemented IOP tests, Domingo, B., Gomez, J., Iglesias, J., Santiago,
on the basis of which it presents a model adapted to J., & Arias, C. (2011). Complementary tests the
Polish conditions. Clear guidelines for the organisa- key of the successful ERTMS deployment in
tion of such tests at both the national and executive Spain.
level are given. Arguments for the implementation [7] CEDEX. (2019). CEDEX, Technical and scien-
of IOP tests in the country are presented. The analy- tific activities. Centro de Publicaciones Secre-
sis conducted in this paper can be used by legislators taría General Técnica Ministerio de Trans-
and infrastructure managers to implement IOP test- portes, Movilidad y Agenda Urbana.
ing in the country by introducing appropriate regu- [8] Chrzan, M. (2021). Study of the possibility of
lations and instructions. The article is therefore an using transmission in the LTE system on a se-
analysis of the possibility to introduce IOP tests in lected railway line for the purpose of running
Poland. railway traffic. Archives of Transport, 57(1),
91–101.
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