It is described in German Published Patent Application No. 35 36 820 and ISO 14819 that traffic messages in the form of digitally encoded messages plus radio programs may be broadcast over radio frequencies to describe traffic-relevant situations, in particular traffic disturbances in the highway system. These TMC (Traffic Message Channel) traffic messages include location information about the location of a traffic disturbance in an encoded form.
ISO 14819 also describes so-called multisequence messages in which traffic information is transmitted in several groups of the RDS signal, but the several groups which include traffic information must always be transmitted in direct succession.
German Published Patent Application No. 199 05 893 describes an expansion of traditional traffic messages according to the TMC standard. It is provided there that a supplementary location description, which is announced in a header preceding the actual message, is to be added to the standardized messages, which regularly contain a location code and thus a reference to a location of a traffic-relevant event. Thus, a location description is no longer limited merely to highway junctions, highway intersections and interchanges and the like and/or the sections in between that are encoded in the TMC location database but instead it allows a further description of the event location.
A more accurate localization of an event location is also the subject of German Published Patent Application No. 100 15 935. It is proposed there that in addition to a section of road affected by a traffic disturbance, which may be defined by an adjacent location encoded in the TMC location database, a portion of a section or comparable linear parameters may also be transmitted, permitting a more accurate localization of the event location on the encoded section of road.
The traffic situations to be transmitted via a traffic message may be simple or complex; for example, “10 km backed-up traffic” is a simple description of the situation and “10 km backed-up traffic, construction site, lane closure, average speed=20 km/h” is a complex description of the situation. Such complex situation descriptions may be described by so-called “multisequence messages,” i.e., multiple indexed successive individual messages in TMC (Traffic Message Channel, as specified in ISO 14819).
One disadvantage here is that all the individual events of a complex situation description must always be based on the same location, i.e., the same section of road, so that the message may be displayed on the terminal as a complex situation description. Furthermore, all the events of a situation must be sent at the same point in time. Although updating is possible, all messages, including all the events they contain, must always be updated. It is impossible to append additional events to a message already sent. Expanded complex example: “Between Laatzen junction and Hildesheim junction 10 km backed-up traffic, construction site, lane closure, average speed=20 km/h.” The individual events of “backed-up traffic,” “construction site,” “lane closure,” and “average speed=20 km/h” must be based on the same location, namely in this case the same section of road between junctions. If the events overlap or if they are based on different neighboring locations, multiple separate messages must be transmitted. It is very complex to combine the messages at the terminal end to allow a compact presentation.
It is also a disadvantage that it is impossible to correlate messages originating from different sources. In the future it may be expected that situation descriptions of differing content will be supplied by different sources. For example, traffic disturbances such as congestion or accidents are compiled by the police via the state reporting offices, while long-term status information such as construction sites or gridlock is supplied by third-party providers—possibly even as a paid service. Example: real situation: “10 km congestion and 5 km construction site.” It is assumed that the construction site will remain in existence for a longer period of time and the message will be transmitted regularly by provider X, e.g., a radio station. Congestion occurs spontaneously and is reported by a state reporting office for a relatively short period of time. With the digitally encoded TMC traffic messages currently being transmitted by radio, there is no possibility of connecting two individual messages to form one complex message.