NP 4398 – Development of an ISO Norm based on railML ®

by Joyce Dillon ( (comments: 0)

ISO’s NP 4398 is a project spearheaded by the Norwegian railway government agency "Norwegian Railway Directorate" which aims to help facilitate data exchange in the railway sector. The norm shall be an open, XML-based, data file format which enables an efficient and unambiguous exchange of static description of a track-bound transportation system, operational functionality of its infrastructure, rolling stock and its timetable. Project leader, Torben Brand, held a presentation at the 36th railML Conference in Brussels regarding the project.

The project is expected to focus on the following use cases: operational timetable, operational simulations of rolling stock, schematic track plans, etc. and seeks to identify and connect the key objects in the proposed standard with the key objects in already existing transportation model standards. The scope explicitly excludes (shall not affect or replace) the following: exchange of public transport schedules, BIM, GIS, TAF/TAP and RINF. However, NP 4398 will observe NeTEx and RINF standards and requirements.

The process

Since NP 4398 was conceived to become a worldwide norm, two ballots at the ISO international level took place: One to accept NP 4398 and begin its development and one to make a liaison organization to ISO.

The voting was held at the beginning of 2020 and yielded in both cases positive results with 16 countries worldwide voting in favor of the proposed norm and 2 voting against it. The liaison vote ended with 18 countries in favor and no negative votes.

What is’s role?

In an effort to facilitate the development, it was proposed to base the standard on railML 2.4, as this is the most complete and mature version to date. However, this does not mean that NP 4398 will be the same as railML. During the development process, there will be changes made and features added, so that the ISO standard will be new and independent aside from having used railML as a basis in the beginning.

It must be noted that any new features that might be stem from the development, and which could be desired by the community, might possibly be implemented in railML 2.5. Version 2.4 will not be altered. Furthermore, will act as a representative of the industry and a guide in working with railML 2.4.

Start-Up Meeting

The meeting took place at the end of March over a telephone conference split into three parts. More than 15 experts from Europe and the USA took part in it and provided the group with their technical and organizational experience. Comments and concerns from the countries that voted were also formally addressed in the round of experts and the final version of the answers will be submitted to ISO.  

From this point forward, development is expected to go on for about 2 years during which the standard will be submitted to multiple revisions and approvals by the members of the ISO committee. The team of experts has begun developing a working draft, which will be the first version of the new standard. A final version is expected to be published in February 2022.

What does this mean for users?

A final version doesn’t mean that everything is set in stone after this point as the standard will be revised 5 years after publishing. To ensure that users are represented as best as we can during the current phase of development, further participants who currently use railML are welcome to join the project. You must not have a lot of technical experience to help out at this stage of the project.

If you would like to know more about NP 4398,’s role or how you may be able to participate, don’t hesitate to contact the Organisational Team per email.


A few weeks after the publishing of the article, the participants in the development team of ISO NP 4398 agreed by means of a vote to give the new standard the name: "railDAX", which is short for "railway DAta eXchange."

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