Road Network Operations
& Intelligent Transport Systems
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In-Vehicle Systems


Satellite Navigation Systems include a routing engine - software that plans the route to the destination. In basic models the route is planned on the basis of a fixed database that describes the road network. (See Basic Info-structure and Navigation and Positioning) More sophisitcated models can take into acount current traffic conditions and provide information on:

  • traffic events
  • weather
  • road conditions
  • in-vehicle signing
  • parking information

Presentation of the information on-screen or by audio must considered in light of human factors and the underlying map interface - the "user interface".(See Systems Approach to ITS Design).

Traffic Information

Traffic information can be coded and distributed digitally as a non-audio data stream over radio. This is how most traffic-enabled Satellite Navigation Systems receive traffic information in real-time. They can then display an icon in relation to the event, alert the driver audibly to it and also prompt the driver to re-route - or automatically amend the route accordingly.

Dynamic Traffic Information

When there is a traffic incident, congestion, or extreme weather event, a data message can be sent to the navigation device. Each event can be assigned a level of severity (impact) in terms of its geographic extent, timing and its likely duration. (See Traffic Incidents) Transmitting these details enables the satellite navigation routing engine to calculate a delay level for the location (the links and junctions in the network that are affected). The software then recalulates the travel time and route options, taking account of this additional delay. Regulations and traffic restrictions may impact on whether automatic re-routing is allowed.

 RDS-TMC Standards

In Europe and North America the main standard for transmission of traffic event data to in vehicle satellite navigation systems is known as RDS-TMC. Information on RDS-TMC can be found from the Traveller Information Services Association website including TMC coverage maps.  A lot of work has been undertaken to standardise the categorisation of events, inparticular the Alert C standard: ISO 14819:2013 - parts 1 and 2 define event categorisation for the RDS-TMC digital transmission system on FM radio.

For TMC to operate there must be a location code table tied to the underlying map network. These location code tables can be developed privately or publically.

Gradually as radio bandwidth becomes scarcer, so it is likely that Digital Audio Broadcasting DAB will take over from FM Analogue radio services.

TPEG STandards

There is a more detailed standard for broadcast of traffic related data over DAB known as TPEG. Practitioners should be mindful of the TPEG standard (ISO TS 18234) for traffic and public transport incident information. This standard makes use of the additional bandwidth available via DAB and the Internet. TPEG is now being widely implemented on digital networks. More information on TPEG can be found via the Traveller Information Services Association website and more specifically in the Introductory Guideline

Both RDS-TMC and TPEG delivery mechanisms allow for the transmission of incident, congestion and weather related messages with TPEG allowing a much richer definition of incidents.

Both TPEG and RDS-TMC can be delivered as open or encypted services dependent on whether these services are to be provided by Government or the Private Sector.



Increasingly, public transport travellers are seeking comfort during their journey about where they are, when they will reach their destination, when they need to alight and what interchange options are available. This information can be presented audibly or visibly and either via a personal mobile device or via an in-vehicle display.

Such information is of particular benefit to tourists and those who are unfamiliar with the route/public transport in question. This may help prioritise where these systems have greatest value. Such systems must be derive information on the stops on the route and must know when these stops have been reached. Most often they are linked to other on vehicle systems, such as ticket machines or automatic vehicle location systems. (See  Passenger Transport) It is critically important to ensure robust operation of such systems making sure that they can be automatically updated if the vehicle is moved between routes. As with other display types, the following must be considered:

  • Visibility and the impact of direct sunlight on legibility/readability
  • Water and Dust Ingress Protection and Impact Protection
  • Data communications to or from the display must be considered noting the in vehicle environment and levels of vibration anticipated
  • Web design guidance WC3 web accessibility standards and guidance and data security (See  Data Regulation and Security)


A TfT screen inside the vehicle can provide additional public transport information, such as disruption to services, further connections available from the forthcoming stop, or the full route or network outline amongst others; such systems rely heavily on vehicle location systems and on accurate information about scheduling and routing. Information about the city, regional events, and tourist information can be interspersed throughout.


The use of wi-fi technology continues to increase, and the provision of such services on-board public transport is often seen as being key to attracting passengers against the perceived convenience of private motor travel, as it offers “value-added” time to the commute or journey.


In the context of long-distance rail travel, several providers have experimented with replacing paper reservation slips on seats with electronic displays, informing passengers of where seats are booked from and to. This enables seat allocations to be clearer for all users, although the reliability of some systems has been called into question. The need to “download” the latest seat configuration before the journey is not always met, in which case reservations cannot be applied to the given journey, causing customer dissatisfaction.


Reference sources

International Standards Organisation (2013) ISO 14819-2:2013 Intelligent transport systems -- Traffic and travel information messages via traffic message coding -- Part 2: Event and information codes for Radio Data System -- Traffic Message Channel (RDS-TMC) using ALERT-C

International Standards Organisation (2013) ISO/TS 18234-1:2013 Intelligent transport systems -- Traffic and travel information via transport protocol experts group, generation 1 (TPEG1) binary data format -- Part 1: Introduction, numbering and versions (TPEG1-INV)