Real-time traffic information and its application in vehicle infotainment system

Real-time traffic information and its application in vehicle infotainment system

With the continuous development of automotive electronics, more and more car navigation systems are installed on the market. Navigation systems that use GPS signals and vehicle sensor data are still the mainstream of China's vehicle navigation equipment. However, car navigation systems that support real-time traffic information have been in Europe, America and Japan for more than 10 years. The so-called real-time traffic information here refers to the road condition information wirelessly transmitted by devices such as broadcasting and the network, and sometimes other traffic information including parking lot vacancies and the like. The information has real-time characteristics. Just like the driver listening to the traffic information radio station while driving, the driver can select the appropriate driving route to reach the destination in time according to the congested and unobstructed traffic conditions. Obviously, a car navigation system with real-time traffic information can bring convenience to the driver, and can also relieve the road traffic pressure on congested and frequent road sections.

Currently, the main application standards for real-time traffic information are TMC (Traffic Message Channel) in Europe and VICS (Vehicle InformaTIon and CommunicaTIon System) in Japan.


TMC basically developed independently in Europe. In 1997, the TMC Forum was established. The forum has been responsible for maintaining and managing the RDS-TMC standard and its application in the European commercial and public service community. The coding standard of TMC is ALERT-C or ALERT-Plus (Advice and Problem LocaTIon for European Road Traffic, the suggestion and problem location of European road traffic). This standard has been accepted by the International Organization for Standardization ISO, ISO14819. As a digital signal, TMC can be broadcast through multiple channels, such as RDS, DAB and SDARS.

A standard TMC ALERT_C message should include the following:

· Event (Event Code, also known as Traffic Management Data DicTIonary)

· Location (Location Code)

· Direction (Direction +/-)

· Event Extension

· Duration (Duration and Persistence)

· Route Advice (Diversion Advice)

If more information is needed, it can be expanded. To decode TMC information, you must know the Country Code and Location Table.

In Europe and North America, the coverage of TMC information broadcast by FM FM radio through RDS is very high, and the basic service is free, generally known as RDS-TMC. The so-called free, refers to two aspects, one is to receive information for free, the other is free of location list-the entire Europe will have a unified location list.

An important advantage of TMC is that its information is language independent. For example, a German traveler takes her German navigation device to travel to France. As long as the French location list is loaded, her navigation device can still remind her of the real-time local traffic conditions in France in French. However, because the transmission rate of RDS-TMC is limited, and it is not conducive to the effective encryption of information, RDS-TMC is easily tampered and forwarded, which is potentially dangerous.

In 1998, TPEG (Traffic Protocol Experts Group) began to design and develop multi-mode tourism and traffic information protocols, and in 2004, the first TPEG standard was published through ISO. Although the standard is not fully compatible with TMC, but after years of unremitting efforts, the application of TPEG has been able to be applied to different regions and different receiving equipment. Since then, the German project led by BMW has begun to define traffic information business service technology based on TMC and TPEG protocols.

At the critical moment of diversification of real-time traffic information standards, a new non-profit organization-TISA (Traveler Information Services Association) was established in Europe in 2007. The association will take over all plans and functions of the TMC Forum, TPEG Forum and project, and create an international unified framework for transportation and tourism information services and products based on existing standards such as RDS-TMC and TPEG. The new framework will focus on the comprehensive application of the advantages of existing standards, especially the promotion of TMC and TPEG standards to the world, making such services more competitive in the market, thereby avoiding the negative market effects brought about by the diversification of standards.


As the earliest country to develop and use civil navigation products, Japan also has its own unique plan for real-time traffic information. In fact, VICS information is transmitted through three channels:

· Infrared signal transmitter: installed on the main open road, used to transmit real-time traffic information within 30 kilometers along the road, the signal of a single transmitter can cover a range of several square meters, equivalent to the size of a car;

Radio frequency signal transmitter: installed on the main highway, used to transmit real-time traffic information within 200 kilometers along the road, the signal of a single transmitter can cover a range of about 70 meters in radius;

· Dedicated FM radio channel (VICS-FM): used to broadcast real-time traffic information in a large area.

VICS information content is very rich, it includes road traffic information, traffic restriction information and parking space information. Although end users receive VICS information for free, manufacturers of VICS receivers need to join the VICS center (pay an annual fee) and pay (by shipment) to produce VICS receivers. General navigation equipment only has VICS-FM receivers, but the VICS center encourages manufacturers to produce VICS navigation equipment with all three types of receivers, because it can obtain more accurate and timely traffic information.

Since the establishment of the VICS Center in 1995, VICS services have covered most of Japan, and its service quality and product quality have been well received by users.

Practical application

The application of real-time traffic information in car navigation equipment can have different levels of design. In terms of hardware, in order not to affect the user's normal listening to radio and other infotainment facilities, car navigation equipment usually equips a special tuner for receiving real-time traffic information. The tuner will work quietly: receive and process traffic information along the way. This information should finally be handed over to the navigation software for further processing.

Real-time traffic information contains a lot of content, and navigation software usually filters the information as needed when processing real-time traffic information. If the user sets a destination, the traffic information from the current location to the destination is very important. In-vehicle infotainment systems with navigation functions usually use enlarged maps of intersections and voice navigation prompts to assist the driver in choosing the travel route. However, driving is not allowed to carefully study the display content on the screen. How to make the display content clear is an important issue in the design of navigation software. The screen processing of real-time traffic information should also be concise.

On the on-screen map, the simplest application of real-time traffic information is to use different colors to represent the traffic situation of the road. For example, if the road is dyed green, the traffic is in good condition and the average speed is higher than 60 km / h. Yellow indicates that the traffic is slightly blocked and the average speed is higher than 30 km / h. The driver takes a brief look at the map to know which road to choose. On the map, various icons can also be used to represent different real-time traffic information along the way. If you click (touch screen) or select (non-touch screen) these icons, more detailed information will be displayed in text in the dialog box. For the information that will seriously affect the expected time to reach the destination, the request to recalculate the route will also be displayed in the form of a dialog box, and the user can decide whether to recalculate the route based on the traffic information. Furthermore, the navigation system can also directly remind users of relevant road conditions in the form of voice, and ask users whether to make route changes based on the information.

A well-designed navigation system will make full use of real-time traffic information to help travellers reach their destinations smoothly, while at the same time averaging the traffic flow on the road to ease the pressure on road traffic.


As the world's fastest-growing car market, China will have more and more cars on the road, and the pressure on road traffic will also increase. The establishment of a real-time traffic information system and the loading of an in-vehicle infotainment system with real-time traffic information processing functions are very beneficial to travelers and to traffic management departments.

To establish a real-time traffic information system, we must first establish standards. In order to be in line with international standards, the selection of standards will generally be made between TMC, TPEG in Europe and VICS in Japan. According to historical experience, the possibility of formulating new standards in line with China's actual conditions is also very high. For example, China can formulate a unified national location list according to TMC and other standards, and the broadcast method can use China's existing digital TV terrestrial broadcasting (DTMB). Although China's real-time traffic information broadcasting standards have not yet been finalized, China and Europe have accepted RDS-TMC as part of future standards through the DYNASTY project. Perhaps DTMB-TMC will become the next hot term.

While establishing standards, it is also necessary to train and certify a batch of professionally qualified information collection and editing units. These units can start from major cities in China, collect real-time road traffic information, and submit it to the information center for processing and broadcasting.

The business model of China's real-time traffic information service should also lean towards public services, that is, end users receive it for free. This is conducive to the popularization of the application and the relief of traffic pressure, and will actually reduce government investment in traffic management in the long run.

Summary of this article

This article introduces real-time traffic information and its application in car navigation, so that designers and manufacturers engaged in the development of in-vehicle infotainment systems can understand and prepare for future new applications.

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