DATEX II operates similarly to a letter, DATEX II itself being the language and the paper upon which the letter is written. Just like a letter, it has a specific purpose, and for this reason there are profiles, making up the predefined form for its specific purpose. Since there is a broad variety of information that is communicated, DATEX II Light is available, which can be understood as a simpler phrasebook or abridged version of the full-form letter.
A letter depends on more than just paper and the written word. It also needs to be sealed and delivered. DATEX II is therefore ‘packaged’ in two forms, either ‘XML’ or ‘JSON’. While the current delivery system is standard IT, alternative delivery methods can be developed as needed.
The Postal system uses standard IT:
Information exchanged with DATEX II systems is composed of different basic elements:
These elements will be explained in further detail. In addition, there are also Predefined Locations, Parking table, VMS Table, and Measurement Site Table information exchanged. They are not part of the basic elements, but are required if the corresponding information in the basic elements is to be understood by a client.
Operator actions are classified in 4 main categories:
It contains, in particular, information on lane availability and on delays (in seconds, in time range or globally).
These sets of data can be derived from direct inputs from outstations or equipments at specific measurement sites (e.g. loop detection sites or weather stations) which are received on a regular (normally frequent) basis, or can derived on a periodic basis by the Traffic Centre from input data for specified locations:
They can be forecast values.
It means information about a service which may influence the behaviour of drivers and hence the characteristics of the traffic flow, i.e.:
These data sets include different possible messages according to different technologies, including textual messages, pictograms or combinations as well as allowing for full matrix VMS. They are completed by some information about equipment status and position.
The previous basic elements can be exchanged individually or grouped. For these exchanges, the notion of publication is used. There are 5 main publications:
A situation publication can contain several different situations.
A situation represents a traffic/travel situation comprising one or more traffic/travel circumstances which are linked by one or more causal relationships and which apply to related locations. Each traffic/travel circumstance is represented by a Situation Record.
A situation record is one element of a situation. It is characterized by values at a given time, defining one version of this element. When these values change, a new version is created. One situation record can be:
and can contain:
This publication is used to send periodically elaborated data derived by a Traffic Centre relating to specified locations. Locations may be explicitly defined in the publication or, more simply, may be referred to by references to predefined locations which have been exchanged via the “predefined locations” publication.
This publication is used to send periodically measured data which has been derived from equipment at specific measurement sites, where each site is identified by reference to an entry in a predefined measurement site table. The measurement site table can be exchanged via the “measurement site table” publication and provides for each site the details of its location and parameters associated with the different types of measurements that can be made at the site.
Each set of measurements from a site is ordered (i.e. indexed), where each ordered measurement might be of a different type. The order (or indexing) of these measurements for each site within the Measured Data publication must correspond with the ordered (indexed) definition of the measurement in the Measurement Site Table publication for the particular site.
This publication is used to send periodically messages elaborated by a Traffic Control Centre relating to a set of display equipments among a road network. Static VMS characteristics may be explicitly defined in the publication (for mobile VMS e.g.) or, more simply, may be referred to by references to predefined VMS installations which have already been exchanged via the “VMS table” publication.