Intelligent transport systems — Roadside modules SNMP data interface — Part 10: Variable message signs

Variable message signs (VMSs) are installed in areas where traffic managers identify a frequent need to convey information to the travelling public, such as upstream from interchanges to alert the public to downstream congestion in time for them to alter their routes. This allows traffic managers to improve the efficiency, safety, and quality of traveller journeys. In order to manage the operation of a VMS and the messages displayed, information exchange between the management systems and the VMS is needed. This document identifies basic user needs for the management of light-emitting diode (LED) matrix VMSs and traces these needs to interoperable designs. This includes the ability to identify the device, its capabilities, and its status. NOTE 1 This document is similar to portions of NTCIP 1203 v03, which defines how to manage VMSs using an older version of SNMP and is a normative reference in this document. NOTE 2 ISO 20684-1 provides additional details about how this series of standards relates to the overall ITS architecture.

Systèmes de transport intelligents — Interface de données SNMP pour les modules en bord de route — Partie 10: Panneaux à messages variables

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Publication Date
06-Apr-2021
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6060 - International Standard published
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TECHNICAL ISO/TS
SPECIFICATION 20684-10
First edition
2021-04
Intelligent transport systems —
Roadside modules SNMP data
interface —
Part 10:
Variable message signs
Systèmes de transport intelligents — Interface de données SNMP pour
les modules en bord de route —
Partie 10: Panneaux à messages variables
Reference number
ISO/TS 20684-10:2021(E)
ISO 2021
---------------------- Page: 1 ----------------------
ISO/TS 20684-10:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/TS 20684-10:2021(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Symbols and abbreviated terms ........................................................................................................................................................... 2

5 Conformance ............................................................................................................................................................................................................. 3

6 Physical architecture ...................................................................................................................................................................................... 6

7 User needs ................................................................................................................................................................................................................... 6

7.1 Manage the control mode of the VMS.................................................................................................................................. 6

7.2 Manage the sign display .................................................................................................................................................................. 7

7.3 Monitor the sign display doors ................................................................................................................................................. 7

7.4 Monitor the sign display mains power ............................................................................................................................... 7

7.5 Monitor the sign display power supplies ......................................................................................................................... 7

8 Requirements .......................................................................................................................................................................................................... 7

8.1 Message sign control mode .......................................................................................................................................................... 7

8.1.1 Message sign control mode definition .......................................................................................................... 7

8.1.2 Message sign control mode data exchange requirements ........................................................... 7

8.1.3 Message sign control mode capabilities ...................................................................................................... 8

8.2 Message library ...................................................................................................................................................................................... 8

8.2.1 Message library definition ....................................................................................................................................... 8

8.2.2 Message library data exchange requirements ........................................................................................ 8

8.2.3 Message library capabilities................................................................................................................................10

8.3 Sign display .............................................................................................................................................................................................12

8.3.1 Sign display definition ........................................................................................................................................... ...12

8.3.2 Sign display data exchange requirements...............................................................................................12

8.4 Sign display doors .............................................................................................................................................................................14

8.4.1 Sign display doors definition ..............................................................................................................................14

8.4.2 Sign display doors data exchange requirements .................. .............................................................14

8.4.3 Sign display door capability requirements ............................................................................................14

8.4.4 Sign display door design constraints ..........................................................................................................14

8.5 Sign display mains power ...........................................................................................................................................................14

8.5.1 Sign display mains power definition ...........................................................................................................14

8.5.2 Sign display mains power data exchange requirements ............................................................14

8.5.3 Sign display mains power capability requirements .......................................................................14

8.5.4 Sign display mains power design constraints .....................................................................................14

8.6 Sign display power supplies .....................................................................................................................................................15

8.6.1 Sign display power supplies definition .....................................................................................................15

8.6.2 Sign display power supplies exchange requirements ...................................................................15

8.6.3 Sign display power supplies capability requirements .................................................................15

8.6.4 Sign display power supplies design constraints ................................................................................15

8.7 Sign display light sensors ............................................................................................................................................................15

8.7.1 Sign display light sensors definition ............................................................................................................15

8.7.2 Sign display light sensors exchange requirements .........................................................................15

8.7.3 Sign display light sensors capability requirements ........................................................................15

8.7.4 Sign display light sensors design constraints ......................................................................................16

8.8 Sign display pixels .............................................................................................................................................................................16

8.8.1 Sign display pixels definition .............................................................................................................................16

8.8.2 Sign display pixels data exchange requirements ..............................................................................16

8.8.3 Sign display pixels capability .............................................................................................................................16

Annex A (normative) Management Information Base ....................................................................................................................17

© ISO 2021 – All rights reserved iii
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ISO/TS 20684-10:2021(E)

Annex B (normative) Requirements Traceability Matrix ............................................................................................................21

Annex C (informative) Relationship to NTCIP 1203 ...........................................................................................................................26

Bibliography .............................................................................................................................................................................................................................27

iv © ISO 2021 – All rights reserved
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ISO/TS 20684-10:2021(E)
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 non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

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. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 204, Intelligent transport systems.

A list of all parts in the ISO 20684 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
© ISO 2021 – All rights reserved v
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ISO/TS 20684-10:2021(E)
Introduction
0.1 Background

A variable message sign (hereinafter referred to as a “VMS”) is an electronic traffic sign installed on

the roadside to provide real-time traffic information to travellers, thereby improving their efficiency

in the utilization of road traffic, and is a major physical component of the intelligent transport system

(hereinafter referred to as “ITS”) which supplies the system with information for improvement of the

safety on the road.

More VMSs are expected to be installed and operated due to an increase in demand for establishment of

ITS and for replacement of existing VMSs which have exceeded their durability terms.

The operator of the traffic management centre needs real time data exchange between a VMS and the

centre to supply information to the VMS in real time and to control and manage the VMS.

However, no standards for the information transmitted and received between the traffic management

centre and the VMSs have been established, leading to the development of various protocols and their

application to each VMS construction project. As a result, a variety of problems have arisen, including

redundant investment in development costs and forced dependence on the protocol of the previous

operator when replacing the existing VMSs with new ones.

This document therefore defines the data items (messages), formats and communication protocols

(Application, Presentation, Session, and Transport layers) required to ensure the interoperability of the

information transmitted and received between the VMS and the traffic management centre, thereby

ensuring interoperability between the VMS and the centre.
0.2 Overview

This document defines the message, the data elements making up the message, and the application

layer profile for message transmission in order to ensure the interoperability between the VMS and the

traffic management centre.

In particular, in order to ensure the interoperability between the VMS and the traffic management

centre, the interoperability is developed based on OSI (open system interconnection) 7 layers. A

collection of standard protocols for each layer is referred to as a "profile."

ISO/IEC TR 10000-2 defines the basic classification and object presentation of OSI profiles as follows:

a) Interchange Format and Representation profiles define the information on and message structure

of the data exchanged by applications.

b) Application profiles define the transmission mechanism for data exchange (concerning OSI layers 5

to 7 — Session, Presentation, and Application layers).

c) Transport profiles define the procedures and methods for exchanging data packets between

systems (concerning OSI layers 1 to 4 — Transport, Network, Data Link, and Physical layers).

d) Relay profiles define the relaying function which enables the interconnection between systems

while using different transmission profiles.

This document defines "Interchange Format and Representation," defined in ISO/IEC TR 10000-2.

a) Components and data elements of basic messages define the messages and detailed data elements

which the operator of the traffic information system needs for operation of the VMS.

b) The data exchange communication profile defines the procedures and encoding methods for

information exchange between the traffic management centre and the VMS.
vi © ISO 2021 – All rights reserved
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ISO/TS 20684-10:2021(E)
0.3 Document approach and layout
This document defines:
a) Physical architecture for varible message signs (Clause 6).

b) User needs that are deemed to be common to many types of field devices (Clause 7).

c) Requirements for implementing the identified user needs, organized by major feature (Clause 8).

d) The management information base (MIB) for the features defined by this document (Annex A).

e) A requirements traceability table that traces requirements to the design elements (Annex B).

f) The relationship to NTCIP 1203 (Annex C).

In addition, a simplified version of the conformance table and the MIBs are available electronically at

https:// standards .iso .org/ iso/ ts/ 20684/ -10/ ed -1/ en.
© ISO 2021 – All rights reserved vii
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TECHNICAL SPECIFICATION ISO/TS 20684-10:2021(E)
Intelligent transport systems — Roadside modules SNMP
data interface —
Part 10:
Variable message signs
1 Scope

Variable message signs (VMSs) are installed in areas where traffic managers identify a frequent need

to convey information to the travelling public, such as upstream from interchanges to alert the public to

downstream congestion in time for them to alter their routes. This allows traffic managers to improve

the efficiency, safety, and quality of traveller journeys.

In order to manage the operation of a VMS and the messages displayed, information exchange between

the management systems and the VMS is needed.

This document identifies basic user needs for the management of light-emitting diode (LED) matrix

VMSs and traces these needs to interoperable designs. This includes the ability to identify the device,

its capabilities, and its status.

NOTE 1 This document is similar to portions of NTCIP 1203 v03, which defines how to manage VMSs using an

older version of SNMP and is a normative reference in this document.

NOTE 2 ISO 20684-1 provides additional details about how this series of standards relates to the overall ITS

architecture.
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 20684-1, Intelligent transport systems – Roadside modules SNMP data interface – Part 1: Overview

ISO 20684-2:— , Intelligent transport systems – Roadside modules SNMP data interface – Part 2:

Generalized field device basic management

IETF RFC 3584, Coexistence between Version 1, Version 2, and Version 3 of the Internet-standard Network

Management Framework

NTCIP 1203:2014, National Transportation Communication for ITS Protocol — Object Definitions for

Dynamic Message Signs (DMS)
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 20684-1 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/

1) Under preparation. Stage at the time of publication: ISO/PRF TS 20684-2:2021.

© ISO 2021 – All rights reserved 1
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ISO/TS 20684-10:2021(E)
3.1
architecture

fundamental concepts or properties of a system in its environment embodied in its elements,

relationships, and in the principles of its design and evolution
[SOURCE: ISO/IEC/IEEE 42010:2011, 3.2]
3.2
centre system

ITS component that provides application, management, and/or administrative functions from a

centralized location (i.e. not at the roadside)
3.3
intelligent transport system
ITS
technology system that is designed to benefit a surface transport system
3.4
message

data concept that is a grouping of data elements, data frames, or data elements and data frames that is

used to convey a complete set of information
3.5
traffic management system
centre system (3.2) that monitors and controls traffic and the road network
3.6
variable message sign
VMS
field device that can display real-time traveller information to the public

Note 1 to entry: A VMS typically consists of one sign display, one sign controller, a cabinet that houses the sign

controller and potentially other components.
4 Symbols and abbreviated terms
ASCII American Standard Code for Information Interchange
ASN.1 Abstract Syntax Notation One
CRC cyclical redundancy check
I/O input/output
MULTI markup language for transportation information
MIB management information base
NTCIP national transportation communications for ITS protocol
RFC request for comments
NOTE RFCs published by the Internet Engineering Task Force
SNMP simple network management protocol
UTF-8 universal coded character set transformation format – 8-bit
2 © ISO 2021 – All rights reserved
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ISO/TS 20684-10:2021(E)
5 Conformance

This conformance section follows the rules defined in ISO 20684-1. Table 1 traces each user need to

a set of software features. Table 2 traces each feature to a set of requirements, in accordance with

ISO 20684-2. For a full understanding of these tables and codes, see ISO 20684-1 .

Table 1 — User need to feature conformance
User need Feature Conformance
Inherited user needs (ISO/TS 20684-2)
ISO/TS 20684-2:—, 7.1: Monitor the field device M
ISO/TS 20684-2:—, 7.3.1: Monitor cabinet doors O
ISO/TS 20684-2:—, 7.3.2: Monitor and control cabinet fans O
ISO/TS 20684-2:—, 7.3.3: Monitor and control heaters O
ISO/TS 20684-2:—, 7.3.4: Monitor cabinet humidity O
ISO/TS 20684-2:—, 7.3.5: Monitor cabinet temperature O
ISO/TS 20684-2:—, 7.3.6: Monitor cabinet AC power O
ISO/TS 20684-2:—, 7.3.7: Monitor cabinet battery power O
ISO/TS 20684-2:—, 7.3.8: Monitor cabinet generator power O
ISO/TS 20684-2:—, 7.3.9: Monitor cabinet solar power O
ISO/TS 20684-2:—, 7.3.10: Monitor cabinet wind power O
User needs defined in this document
7.1: Manage the control mode of the VMS M
8.1: Message sign control mode M
7.2: Manage the sign display (this document) M
8.2: Message library M
8.3: Sign display M
8.7: Sign display light sensors O
8.8: Sign display pixels O
7.3: Monitor the sign display doors O
8.4: Sign display doors M
ISO/TS 20684-2:—, 8.2 General-purpose I/O M
7.4: Monitor the sign display mains power O
8.5: Sign display mains power M
ISO/TS 20684-2:—, 8.2 General-purpose I/O M
7.5: Monitor the sign display power supplies O
8.6: Sign display power supplies M
ISO/TS 20684-2:—, 8.2 General-purpose I/O M

2) The development of the content of this document followed a formal systems engineering process, which entails

(1) defining needs, (2) developing a set of interface requirements, (3) developing features as a part of a high-level

design to meet the requirements, (4) refining the interface requirements from Step 2 to reflect the high-level

design, and (5) developing a low-level design defining the dialogues and data elements necessary to implement

the requirements. The documentation omits the original requirements as they are refined in Step 4 and listing

the original requirements would make the document highly redundant. The revised requirements ensure more

consistent terminology and traceability among the tables.
© ISO 2021 – All rights reserved 3
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ISO/TS 20684-10:2021(E)
Table 2 — Feature to requirement conformance
Feature Requirement (ISO/TS 20684-10, this document) Conformance
8.1: Message sign control mode
8.1.2.1: Configure control mode 8.1.3.2:M
8.1.2.2: Verify control mode M
8.1.3.1: Support central control mode M
8.1.3.2: Support local control mode O
8.1.3.3: Support central override control mode 8.1.3.2:M
8.2: Message library
8.2.2.1: Discover capabilities of the message library M
8.2.2.2: Configure default flash times O
8.2.2.3: Verify default flash times 8.2.2.2:M
8.2.2.4: Configure default page times O
8.2.2.5: Verify default page times 8.2.2.4:M
8.2.2.6: Configure default line justification O
8.2.2.7: Verify default line justification 8.2.2.6:M
8.2.2.8: Configure default page justification O
8.2.2.9: Verify default page justification 8.2.2.8:M
8.2.2.10: Configure default colours M
8.2.2.11: Verify default colours M
8.2.2.12: Configure message encoding M
8.2.2.13: Verify message encoding M
8.2.2.14: Configure a message M
8.2.2.15: Verify message configuration M
8.2.2.16: Verify message code M
8.2.2.17: Retrieve message enabled status M
8.2.2.18: Toggle message enabled status M
8.2.2.19: Delete message M
8.2.2.20: Delete all messages M
8.2.3.1.1: Supported minimum flash time 8.2.2.2:M
8.2.3.1.2: Supported maximum flash time 8.2.2.2:M
8.2.3.1.3: Supported flash time step size 8.2.2.2:M
8.2.3.2.1: Supported minimum page time 8.2.2.4:M
8.2.3.2.2: Supported maximum page time 8.2.2.4:M
8.2.3.2.3: Supported page time step size 8.2.2.4:M
8.2.3.3.1: Line justification – Left 8.2.2.6:M
8.2.3.3.2: Line justification – Centre 8.2.2.6:M
8.2.3.3.3: Line justification – Right 8.2.2.6:M
8.2.3.3.4: Line justification – Full 8.2.2.6:M
8.2.3.4.1: Page justification – Top 8.2.2.8:M
8.2.3.4.2: Page justification – Middle 8.2.2.8:M
8.2.3.4.3: Page justification – Bottom 8.2.2.8:M
8.2.3.5.1: Message encoding – ASCII O.1 (1..*)
The conformance column follows the rules defined in ISO 20684-1:2021, Clause 5.
4 © ISO 2021 – All rights reserved
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ISO/TS 20684-10:2021(E)
Table 2 (continued)
Feature Requirement (ISO/TS 20684-10, this document) Conformance
8.2.3.5.2: Message encoding – UTF-8 O.1 (1..*)
8.2.3.6.1: Circular moving text O
8.2.3.6.2: Linear moving text O
8.3: Sign display
8.3.2.1: Discover characteristics of the sign display M
8.3.2.2: Configure location of sign display M
8.3.2.3: Verify location of sign display M
8.3.2.4: Configure end duration message M
8.3.2.5: Verify end duration message M
8.3.2.6: Display a message on the sign display M
8.3.2.7: Monitor current message M
8.3.2.8: Monitor dynamic fields of current message O
8.4: Sign display doors
8.4.3.1: Sign display doors monitored M
8.4.4.1: Sign display doors monitored through general-purpose I/O M
8.5: Sign display mains power
8.5.3.1: Sign display mains power voltage M
8.5.3.2: Sign display mains power current M

8.5.4.1: Sign display mains power voltage monitored through general-purpose I/O M

8.5.4.2: Sign display mains power current monitored through general-purpose I/O M

8.6: Sign display power supplies
8.6.3.1: Sign display power supplies voltage M
8.6.3.2: Sign display power supplies current M
8.6.4.1: Sign display power supplies voltage monitored through general-pur- M
pose I/O
8.6.4.2: Sign display power supplies current monitored through general-pur- M
pose I/O
8.7: Sign display light sensors
8.7.3.1: Sign display light sensors monitored M
8.7.4.1: Sign display light sensors monitored through general-purpose I/O M
8.8: Sign display pixels
8.8.2.1: Discover characteristics of sign display pixels M
8.8.2.2: Perform pixel test M
8.8.3.1: Sign display pixels monitored M
8.8.3.2: Colourful pixel O
The conformance column follows the rules defined in ISO 20684-1:2021, Clause 5.

Each requirement specifying a need for a data exchange traces to one dialogue and one or more

data elements that an implementation claiming conformance to the requirement shall support.

The traceability from requirements to dialogues and data elements is defined in the Requirements

Traceability Matrix (RTM) as contained in Annex B. Annex B may include references to dialogues and

data elements defined in other documents; any locally defined dialogues shall be defined in the body of

the document, while all data elements shall be defined in Annex A of the document using a Management

Information Base (MIB) conforming to the format defined in IETF RFC 2578.
© ISO 2021 – All rights reserved 5
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ISO/TS 20684-10:2021(E)

If the implementation supports SNMP, all supported data element instances (i.e. SNMP objects) shall be

accessible via any dialogue that meets the requirements of SNMP and the data element definition.

NOTE The dialogues defined in this document are specified to promote a common interface for testing

purposes and are not intended to restrict otherwise allowable requests or notifications. The file for the

maintenance portal can be found at the following address: https:// standards .iso .org/ iso/ ts/ 20684/ -10/ ed -1/ en.

6 Physical architecture

The physical architecture of the key components for a VMS system is depicted in Figure 1. A VMS,

which may be portable or permanent, can be controlled from either a centre system (such as a traffic

management system) or field support equipment (such as a laptop computer). The telecommunications

network between these units can be wired or wireless. The local VMS typically includes a roadside

module containing a processor and a sign display that displays the actual message, typically through a

matrix of pixels.
Figure 1 — View of a physical architecture
This document is only concerned with the interface between an e
...

TECHNICAL ISO/TS
SPECIFICATION 20684-10
First edition
Intelligent transport systems —
Roadside modules SNMP data
interface —
Part 10:
Variable message signs
Systèmes de transport intelligents — Interface de données SNMP pour
les modules en bord de route —
Partie 10: Panneaux à messages variables
PROOF/ÉPREUVE
Reference number
ISO/TS 20684-10:2021(E)
ISO 2021
---------------------- Page: 1 ----------------------
ISO/TS 20684-10:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2021

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting

on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address

below or ISO’s member body in the country of the requester.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii PROOF/ÉPREUVE © ISO 2021 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/TS 20684-10:2021(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Symbols and abbreviated terms ........................................................................................................................................................... 2

5 Conformance ............................................................................................................................................................................................................. 3

6 Physical architecture ...................................................................................................................................................................................... 6

7 User needs ................................................................................................................................................................................................................... 6

7.1 Manage the control mode of the VMS.................................................................................................................................. 6

7.2 Manage the sign display .................................................................................................................................................................. 7

7.3 Monitor the sign display doors ................................................................................................................................................. 7

7.4 Monitor the sign display mains power ............................................................................................................................... 7

7.5 Monitor the sign display power supplies ......................................................................................................................... 7

8 Requirements .......................................................................................................................................................................................................... 7

8.1 Message sign control mode .......................................................................................................................................................... 7

8.1.1 Message sign control mode definition .......................................................................................................... 7

8.1.2 Message sign control mode data exchange requirements ........................................................... 7

8.1.3 Message sign control mode capabilities ...................................................................................................... 8

8.2 Message library ...................................................................................................................................................................................... 8

8.2.1 Message library definition ....................................................................................................................................... 8

8.2.2 Message library data exchange requirements ........................................................................................ 8

8.2.3 Message library capabilities................................................................................................................................10

8.3 Sign display .............................................................................................................................................................................................12

8.3.1 Sign display definition ........................................................................................................................................... ...12

8.3.2 Sign display data exchange requirements...............................................................................................12

8.4 Sign display doors .............................................................................................................................................................................14

8.4.1 Sign display doors definition ..............................................................................................................................14

8.4.2 Sign display doors data exchange requirements .................. .............................................................14

8.4.3 Sign display door capability requirements ............................................................................................14

8.4.4 Sign display door design constraints ..........................................................................................................14

8.5 Sign display mains power ...........................................................................................................................................................14

8.5.1 Sign display mains power definition ...........................................................................................................14

8.5.2 Sign display mains power data exchange requirements ............................................................14

8.5.3 Sign display mains power capability requirements .......................................................................14

8.5.4 Sign display mains power design constraints .....................................................................................14

8.6 Sign display power supplies .....................................................................................................................................................15

8.6.1 Sign display power supplies definition .....................................................................................................15

8.6.2 Sign display power supplies exchange requirements ...................................................................15

8.6.3 Sign display power supplies capability requirements .................................................................15

8.6.4 Sign display power supplies design constraints ................................................................................15

8.7 Sign display light sensors ............................................................................................................................................................15

8.7.1 Sign display light sensors definition ............................................................................................................15

8.7.2 Sign display light sensors exchange requirements .........................................................................15

8.7.3 Sign display light sensors capability requirements ........................................................................15

8.7.4 Sign display light sensors design constraints ......................................................................................16

8.8 Sign display pixels .............................................................................................................................................................................16

8.8.1 Sign display pixels definition .............................................................................................................................16

8.8.2 Sign display pixels data exchange requirements ..............................................................................16

8.8.3 Sign display pixels capability .............................................................................................................................16

Annex A (normative) Management Information Base ....................................................................................................................17

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Annex B (normative) Requirements Traceability Matrix ............................................................................................................21

Annex C (informative) Relationship to NTCIP 1203 ...........................................................................................................................26

Bibliography .............................................................................................................................................................................................................................27

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ISO/TS 20684-10:2021(E)
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 non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

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. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 204, Intelligent transport systems.

A list of all parts in the ISO 20684 series can be found on the ISO website.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
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ISO/TS 20684-10:2021(E)
Introduction
0.1 Background

A variable message sign (hereinafter referred to as a “VMS”) is an electronic traffic sign installed on the

roadside to provide real-time traffic information to travellers, thereby improving their efficiency in the

utilization of road traffic, and is a major physical component of the intelligent transportation system

(hereinafter referred to as “ITS”) which supplies the system with information for improvement of the

safety on the road.

More VMSs are expected to be installed and operated due to an increase in demand for establishment of

ITS and for replacement of existing VMSs which have exceeded their durability terms.

The operator of the traffic management centre needs real time data exchange between a VMS and the

centre to supply information to the VMS in real time and to control and manage the VMS.

However, no standards for the information transmitted and received between the traffic management

centre and the VMSs have been established, leading to the development of various protocols and their

application to each VMS construction project. As a result, a variety of problems have arisen, including

redundant investment in development costs and forced dependence on the protocol of the previous

operator when replacing the existing VMSs with new ones.

This document therefore defines the data items (messages), formats, and communication protocols

(Application, Presentation, Session, and Transport layers) required to ensure the interoperability of the

information transmitted and received between the VMS and the traffic management centre, thereby

ensuring interoperability between the VMS and the centre.
0.2 Overview

This document defines the message, the data elements making up the message, and the application

layer profile for message transmission in order to ensure the interoperability between the VMS and the

traffic management centre.

In particular, in order to ensure the interoperability between the VMS and the traffic management

centre, the interoperability is developed based on OSI (open system interconnection) 7 layers. A

collection of standard protocols for each layer is referred to as a "profile."

ISO/IEC TR 10000-2 defines the basic classification and object presentation of OSI profiles as follows:

a) Interchange Format and Representation profiles define the information on and message structure

of the data exchanged by applications.

b) Application profiles define the transmission mechanism for data exchange (concerning OSI layers 5

to 7 - Session, Presentation, and Application layers).

c) Transport profiles define the procedures and methods for exchanging data packets between

systems (concerning OSI layers 1 to 4 - Transport, Network, Data Link, and Physical layers).

d) Relay profiles define the relaying function which enables the interconnection between systems

while using different transmission profiles.

This document defines "Interchange Format and Representation," defined in ISO/IEC TR 10000-2.

a) Components and data elements of basic messages define the messages and detailed data elements

which the operator of the traffic information system needs for operation of the VMS.

b) The data exchange communication profile defines the procedures and encoding methods for

information exchange between the traffic management centre and the VMS.
0.3 Document approach and layout
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ISO/TS 20684-10:2021(E)
This document defines:
a) Physical architecture for varible message signs (Clause 6).

b) User needs that are deemed to be common to many types of field devices (Clause 7).

c) Requirements for implementing the identified user needs, organized by major feature (Clause 8).

d) The management information base (MIB) for the features defined by this document (Annex A).

e) A requirements traceability table that traces requirements to the design elements (Annex B).

f) The relationship to NTCIP 1203 (Annex C).

In addition, a simplified version of the conformance table and the MIBs are available electronically at

https:// standards .iso .org/ iso/ ts/ 20684/ -10/ ed -1/ en.
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TECHNICAL SPECIFICATION ISO/TS 20684-10:2021(E)
Intelligent transport systems — Roadside modules SNMP
data interface —
Part 10:
Variable message signs
1 Scope

Variable message signs (VMSs) are installed in areas where traffic managers identify a frequent need

to convey information to the travelling public, such as upstream from interchanges to alert the public to

downstream congestion in time for them to alter their routes. This allows traffic managers to improve

the efficiency, safety, and quality of traveller journeys.

In order to manage the operation of a VMS and the messages displayed, information exchange between

the management systems and the VMS is needed.

This document identifies basic user needs for the management of light-emitting diode (LED) matrix

VMSs and traces these needs to interoperable designs. This includes the ability to identify the device,

its capabilities, and its status.

NOTE 1 This document is similar to portions of NTCIP 1203 v03, which defines how to manage VMSs using an

older version of SNMP and is a normative reference to this document.

NOTE 2 ISO 20684-1 provides additional details about how this series of standards relate to the overall ITS

architecture.
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 20684-1:— , Intelligent transport systems – Roadside modules SNMP data interface – Part 1: Overview

ISO 20684-2:— , Intelligent transport systems – Roadside modules SNMP data interface – Part 2:

Generalized field device basic management

IETF RFC 3584, Coexistence between Version 1, Version 2, and Version 3 of the Internet-standard Network

Management Framework

NTCIP 1203:2014, National Transportation Communication for ITS Protocol — Object Definitions for

Dynamic Message Signs (DMS)
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 20684-1 and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
1) Under preparation. Stage at the time of publication: ISO/FDIS 20684-1:2021
2) Under preparation. Stage at the time of publication: ISO/DTS 20684-2:2021.
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ISO/TS 20684-10:2021(E)
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
architecture

fundamental concepts or properties of a system in its environment embodied in its elements,

relationships, and in the principles of its design and evolution
[SOURCE: ISO/IEC/IEEE 42010:2011, 3.2]
3.2
centre system

ITS component that provides application, management, and/or administrative functions from a

centralized location (i.e. not at the roadside)
3.3
intelligent transport system
ITS
technology system that is designed to benefit a surface transport system
3.4
message

data concept that is a grouping of data elements, data frames, or data elements and data frames that is

used to convey a complete set of information
3.5
traffic management system
centre system (3.2) that monitors and controls traffic and the road network
3.6
variable message sign
VMS
field device that can display real-time traveller information to the public

Note 1 to entry: A VMS typically consists of one sign display, one sign controller, a cabinet that houses the sign

controller and potentially other components.
4 Symbols and abbreviated terms
ASCII American Standard Code for Information Interchange
ASN.1 Abstract Syntax Notation One
CRC cyclical redundancy check
I/O input/output
MULTI markup language for transportation information
MIB management information base
NTCIP national transportation communications for ITS protocol
RFC request for comments
NOTE RFCs published by the Internet Engineering Task Force
SNMP simple network management protocol
UTF-8 universal coded character set transformation format – 8-bit
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ISO/TS 20684-10:2021(E)
5 Conformance

This conformance section follows the rules defined in ISO 20684-1. Table 1 traces each user need to

a set of software features. Table 2 traces each feature to a set of requirements, in accordance with

ISO 20684-2. For a full understanding of these tables and codes, see ISO 20684-1 .

Table 1 — User need to feature conformance
User need Feature Conformance
Inherited user needs (ISO/TS 20684-2)
ISO/TS 20684-2, 7.1: Monitor the field device M
ISO/TS 20684-2, 7.3.1: Monitor cabinet doors O
ISO/TS 20684-2, 7.3.2: Monitor and control cabinet fans O
ISO/TS 20684-2, 7.3.3: Monitor and control heaters O
ISO/TS 20684-2, 7.3.4: Monitor cabinet humidity O
ISO/TS 20684-2, 7.3.5: Monitor cabinet temperature O
ISO/TS 20684-2, 7.3.6: Monitor cabinet AC power O
ISO/TS 20684-2, 7.3.7: Monitor cabinet battery power O
ISO/TS 20684-2, 7.3.8: Monitor cabinet generator power O
ISO/TS 20684-2, 7.3.9: Monitor cabinet solar power O
ISO/TS 20684-2, 7.3.10: Monitor cabinet wind power O
User needs defined in this document
7.1: Manage the control mode of the VMS M
8.1: Message sign control mode M
7.2: Manage the sign display (this document) M
8.2: Message library M
8.3: Sign display M
8.7: Sign display light sensors O
8.8: Sign display pixels O
7.3: Monitor the sign display doors O
8.4: Sign display doors M
ISO/TS 20684-2, 8.2 General-purpose I/O M
7.4: Monitor the sign display mains power O
8.5: Sign display mains power M
ISO/TS 20684-2, 8.2 General-purpose I/O M
7.5: Monitor the sign display power supplies O
8.6: Sign display power supplies M
ISO/TS 20684-2, 8.2 General-purpose I/O M

3) The development of the content of this document followed a formal systems engineering process, which entails

(1) defining needs, (2) developing a set of interface requirements, (3) developing features as a part of a high-level

design to meet the requirements, (4) refining the interface requirements from Step 2 to reflect the high-level

design, and (5) developing a low-level design defining the dialogues and data elements necessary to implement

the requirements. The documentation omits the original requirements as they are refined in Step 4 and listing

the original requirements would make the document highly redundant. The revised requirements ensure more

consistent terminology and traceability among the tables.
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ISO/TS 20684-10:2021(E)
Table 2 — Feature to requirement conformance
Feature Requirement (ISO/TS 20684-10, this document) Conformance
8.1: Message sign control mode
8.1.2.1: Configure control mode 8.1.3.2:M
8.1.2.2: Verify control mode M
8.1.3.1: Support central control mode M
8.1.3.2: Support local control mode O
8.1.3.3: Support central override control mode 8.1.3.2:M
8.2: Message library
8.2.2.1: Discover capabilities of the message library M
8.2.2.2: Configure default flash times O
8.2.2.3: Verify default flash times 8.2.2.2:M
8.2.2.4: Configure default page times O
8.2.2.5: Verify default page times 8.2.2.4:M
8.2.2.6: Configure default line justification O
8.2.2.7: Verify default line justification 8.2.2.6:M
8.2.2.8: Configure default page justification O
8.2.2.9: Verify default page justification 8.2.2.8:M
8.2.2.10: Configure default colours M
8.2.2.11: Verify default colours M
8.2.2.12: Configure message encoding M
8.2.2.13: Verify message encoding M
8.2.2.14: Configure a message M
8.2.2.15: Verify message configuration M
8.2.2.16: Verify message code M
8.2.2.17: Retrieve message enabled status M
8.2.2.18: Toggle message enabled status M
8.2.2.19: Delete message M
8.2.2.20: Delete all messages M
8.2.3.1.1: Supported minimum flash time 8.2.2.2:M
8.2.3.1.2: Supported maximum flash time 8.2.2.2:M
8.2.3.1.3: Supported flash time step size 8.2.2.2:M
8.2.3.2.1: Supported minimum page time 8.2.2.4:M
8.2.3.2.2: Supported maximum page time 8.2.2.4:M
8.2.3.2.3: Supported page time step size 8.2.2.4:M
8.2.3.3.1: Line justification – Left 8.2.2.6:M
8.2.3.3.2: Line justification – Centre 8.2.2.6:M
8.2.3.3.3: Line justification – Right 8.2.2.6:M
8.2.3.3.4: Line justification – Full 8.2.2.6:M
8.2.3.4.1: Page justification – Top 8.2.2.8:M
8.2.3.4.2: Page justification – Middle 8.2.2.8:M
8.2.3.4.3: Page justification – Bottom 8.2.2.8:M
8.2.3.5.1: Message encoding – ASCII O.1 (1..*)

The conformance column follows the rules defined in ISO 20684-1:— , Clause 5.
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ISO/TS 20684-10:2021(E)
Table 2 (continued)
Feature Requirement (ISO/TS 20684-10, this document) Conformance
8.2.3.5.2: Message encoding – UTF-8 O.1 (1..*)
8.2.3.6.1: Circular moving text O
8.2.3.6.2: Linear moving text O
8.3: Sign display
8.3.2.1: Discover characteristics of the sign display M
8.3.2.2: Configure location of sign display M
8.3.2.3: Verify location of sign display M
8.3.2.4: Configure end duration message M
8.3.2.5: Verify end duration message M
8.3.2.6: Display a message on the sign display M
8.3.2.7: Monitor current message M
8.3.2.8: Monitor dynamic fields of current message O
8.4: Sign display doors
8.4.3.1: Sign display doors monitored M
8.4.4.1: Sign display doors monitored through general-purpose I/O M
8.5: Sign display mains power
8.5.3.1: Sign display mains power voltage M
8.5.3.2: Sign display mains power current M

8.5.4.1: Sign display mains power voltage monitored through general-purpose I/O M

8.5.4.2: Sign display mains power current monitored through general-purpose I/O M

8.6: Sign display power supplies
8.6.3.1: Sign display power supplies voltage M
8.6.3.2: Sign display power supplies current M
8.6.4.1: Sign display power supplies voltage monitored through general-pur- M
pose I/O
8.6.4.2: Sign display power supplies current monitored through general-pur- M
pose I/O
8.7: Sign display light sensors
8.7.3.1: Sign display light sensors monitored M
8.7.4.1: Sign display light sensors monitored through general-purpose I/O M
8.8: Sign display pixels
8.8.2.1: Discover characteristics of sign display pixels M
8.8.2.2: Perform pixel test M
8.8.3.1: Sign display pixels monitored M
8.8.3.2: Colourful pixel O

The conformance column follows the rules defined in ISO 20684-1:— , Clause 5.

Each requirement specifying a need for a data exchange traces to one dialogue and one or more

data elements that an implementation claiming conformance to the requirement shall support.

The traceability from requirements to dialogues and data elements is defined in the Requirements

Traceability Matrix (RTM) as contained in Annex B. Annex B may include references to dialogues and

data elements defined in other documents; any locally defined dialogues shall be defined in the body of

the document, while all data elements shall be defined in Annex A of the document using a Management

Information Base (MIB) conforming to the format defined in IETF RFC 2578.
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ISO/TS 20684-10:2021(E)

If the implementation supports SNMP, all supported data element instances (i.e. SNMP objects) shall be

accessible via any dialogue that meets the requirements of SNMP and the data element definition.

NOTE The dialogues defined in this document are specified to promote a common interface for testing

purposes and are not intended to restrict otherwise allowable requests or notifications. The file for the

maintenance portal can be found at the following address: https:// standards .iso .org/ iso/ ts/ 20684/ -10/ ed -1/ en.

6 Physical architecture

The physical architecture of the key components for a VMS system is depicted in Figure 1. A VMS,

which may be portable or permanent, can be controlled from either a centre system (such as a traffic

management system) or field support equipment (such as a laptop computer). The telecommunications

network between these units can be wired or wireless. The local VMS typically includes a roadside

module containin
...

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