Computerized operations control system
A computer-aided operations control system ( ITCS ) for Intermodal Transport Control System is a computer network system used in public transport that can be used for a variety of tasks. In 2005 the term RBL was replaced by ITCS . In English, the term CAD / AVL (Computer Aided Dispatch / Automatic Vehicle Location) or AVLS (Automatic Vehicle Location System) is common.
The ITCS mainly controls the following areas: information and communication options between vehicle and control center , computer-aided driving, passenger information in trains and buses and at stops , via mobile communications and the Internet , the so-called dynamic passenger information .
Core functionality of the headquarters
The core of every ITCS is the central server software. This collects all operating data that arises, compares it with the original planning data and, within certain limits, reacts independently to the respective operating situation.
Communication between vehicles, headquarters and control center
The ITCS organizes all communication with the control center and the vehicles. This affects both the language (radio calls) and a large number of data. In many cases, analog company and trunked radio systems are still used for this. However, digital radio systems (e.g. TETRA or Tetrapol ) and public mobile radio systems ( GSM ) are also increasingly being used.
Operational information and instructions are primarily given by the control center by means of speech, while the drivers in turn transmit information, for example about the traffic situation or lost property, to the control center. The control center also has the option of addressing several vehicles in a group call at the same time. In this way it is possible to provide information only to the drivers on a line .
Essentially, the location data of the vehicles are transmitted via radio data transmission. In addition, simple information and instructions such as “connection to line 123” or fault messages are transmitted.
The current location of the vehicles is sent to the head office at regular intervals. There are two basic localization variants and a combination of both:
Local public transport is usually organized as a regular service . That means, starting from a defined starting point, a defined route is traveled. It is therefore sufficient, starting from the defined starting point, to record the distance currently covered and to transmit it to the control center. Only a small amount of data, namely the route currently covered, needs to be transmitted. This is particularly beneficial to the old, narrow-band, analog radio data transmission systems. The accuracy is increased by comparing it with information about the stopping point (door release is recognized). However, this method makes it difficult to detect deviations from the line path. This is why system bottlenecks appear when the routes are changed.
The vehicles determine their location using a public positioning system such as GPS or location beacons (via infrared or inductive via coupling coils - historically there were also magnetic beacons on the track ) along the route. The amount of data that arises here is greater than with logical location and therefore places higher demands on the communication systems, but it also records deviations from the course of the line. However, the localization is not always given in difficult situations such as in tunnels and in tight urban areas.
Combination of logical and physical location
In order to compensate for the disadvantages of both of the aforementioned methods, a combination of both variants is used in the modern ITCS.
Determination of the timetable situation
Based on the plan data, a comparison is made with the actual location data in order to determine the current deviation of the timetable for each vehicle. The timetable deviation is usually determined with an accuracy of down to 30 seconds. This accuracy is sufficient, only in underground systems an accuracy of up to ten seconds is required, depending on the network configuration.
A large number of functions are carried out automatically on the basis of the data obtained. The connection fuse is an example. Only if certain limit values are exceeded, such as a long delay, is a message sent to the workstation of the responsible dispatcher. He can then make operational decisions and initiate dispositive measures.
Information and communication option between vehicle and control center
The ITCS provides a constant communication and information option between the vehicle driver and the responsible control center. GPS or infrared beacons along the route enable the location to be determined so that both the driver and the control center are constantly informed of the vehicle's current position and any deviations from the timetable.
The control center is thus given the opportunity to recognize frequently occurring delays in the computer system, e.g. B. in the event of increased traffic or an accident. Based on this information, the control center can set up diversions and instruct the drivers accordingly. The control center can also request the driver via ITCS to secure connections to other lines at certain stops.
In principle, the ITCS not only enables verbal communication between the driver and the control center via radio, but also the option of text messages (e.g. "connection security"), which then appear on the driver's display.
If the course of routes (especially in the case of trams and underground trains ) is already stored in the ITCS, the ITCS can independently set points via radio and request signal releases. The ITCS can also register at traffic lights on buses in order to enable better adherence to schedules or even faster travel speeds through a green wave .
Passenger information on trains and buses
The information stored in the ITCS can also be used to inform passengers acoustically and optically (via displays or screens) about the upcoming stop and any transfer options.
The respective language and text information is digitally stored in the on-board computer and can be accessed at any time. Alternatively, additional information can be announced, for example if the route deviates from the usual route due to an accident or if there is a replacement rail service.
Passenger information at stops, via cellular phone and internet
Finally, via the ITCS, passengers at stops can also be informed about the respective departures via dynamic passenger information displays and via mobile communications and the Internet. The ITCS not only uses the regular timetable data, but also dynamically adapts the actual departure time to the respective situation by interpreting the location information sent by the respective vehicle to the control center.
Stop displays are also suitable for quickly informing passengers of unforeseen or upcoming changes using scrolling texts.
From RBL to ITCS
While the AVL was an isolated system at the beginning, it has been linked with more and more systems over time and thus become a central data hub. In order to do justice to this fact and to meet the wishes of some parts of the industry for an internationally marketable term, the term AVL was replaced by ITCS (Intermodal Transport Control System) in 2005 by a working group of the Association of German Transport Companies (VDV).
However, this decision offers some starting points for criticism. On the one hand, many AVLC systems are not intermodal at all because only a few systems actually control several modes of transport (e.g. trams and buses ). On the other hand, there is a risk of confusion between the German pronunciation of the abbreviation ITCS and the English pronunciation of ETCS, the European Train Control System . Both terms can certainly appear in one context. In addition, the RBL is a term that has been introduced for decades.
That is why the computer-aided operations control system is still used today as a term.