With the continuous development of automotive electronics, more and more car navigation systems are on the market. Navigation systems using GPS signals and vehicle sensor data are still the mainstream of Chinese car 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 refers to road traffic information that is wirelessly transmitted through broadcast, network, and other devices, and sometimes includes other traffic information such as parking space vacancies. This information has the characteristics of real-time, just like the driver listens to the traffic information radio station while driving, the driver can select the appropriate driving route to reach the destination according to the congestion and smooth condition of the heard section. Obviously, the car navigation system with real-time traffic information can bring convenience to the driver, and can also alleviate the road traffic pressure of the congestion-prone road.
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Currently, the main application standards for real-time traffic information are the TMC (Traffic Message Channel) in Europe and the VICS (Vehicle Information and Communication System) in Japan.
TMC
TMC is basically developed independently in Europe. In 1997, the TMC Forum was established. The forum has been responsible for maintaining and managing the RDS-TMC standards and its application to commercial and public service groups in Europe. The coding standard for TMC is ALERT-C or ALERT-Plus (Advice and Problem Location for European Road Traffic). This standard has been accepted by the International Organization for Standardization ISO, ISO14819. TMC can be broadcast as a digital signal in a variety of ways, such as RDS, DAB and SDARS.
A standard TMC ALERT_C message should include the following:
· Event (also known as Traffic Management Data Dictionary)
· Location (Location Code)
· Direction (Direction +/-)
· Event Extension
· Duration and Persistence
· Diversion Advice
If you need more information, you can expand it. To decode TMC information, you must know the Country Code and the Location Table.
In Europe and North America, the coverage of broadcasting TMC information via RDS using FM FM radio is high, and the basic service is free, generally called RDS-TMC. The so-called free, refers to two aspects, one is to receive information free of charge, and the other is a list of places for free - there will be a unified list of locations throughout Europe.
An important advantage of TMC is that its information is language independent. For example, a German traveler travels to France with her German navigation device. As long as she has a list of French locations, her navigation device can still tell her (France) about the real-time traffic conditions in German. However, due to the limited transmission rate of RDS-TMC and the unfavorable encryption of information, RDS-TMC is easily tamper-forwarded and potentially dangerous.
In 1998, TPEG (Traffic Protocol Experts Group) began designing and developing multimodal tourism and traffic information protocols, and in 2004 passed ISO to disclose the first TPEG standard. Although the standard is not fully compatible with TMC, after years of unremitting efforts, TPEG applications have been able to be applied to different regions and different receiving devices. Since then, the German Mobile.info project led by BMW has begun to define traffic information business service technology based on the TMC and TPEG protocols.
At a critical moment in the diversification of real-time traffic information standards, a new non-profit organization, the TISA (Traveler Information Services Association), was established in Europe in 2007. The association will take over all the programs and functions of the TMC Forum, the TPEG Forum and the Mobile.info project and create an internationally 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 combined application of existing standards, in particular the promotion of TMC and TPEG standards worldwide, making these services more competitive in the marketplace, thereby avoiding market negative effects due to standard diversification.
VICS
As the earliest country to develop and use civil navigation products, Japan also has its own unique solutions in real-time traffic information. In fact, VICS information is spread through three channels:
· Infrared signal transmitter: installed on the main open road to transmit real-time traffic information within 30 kilometers of the road. The signal of a single transmitter can cover a range of several square meters, which is equivalent to the size of a car;
· RF signal transmitter: installed on the main highway to transmit real-time traffic information within 200 km of the road. The signal of a single transmitter can cover a radius of about 70 meters.
· Dedicated FM Radio Channel (VICS-FM): Used to broadcast real-time traffic information within a large area.
VICS has a wealth of information, including road patency information, traffic restrictions, and parking space information. Although the end user receives VICS information for free, the VICS receiver manufacturer needs to join the VICS center (pay the annual fee) and pay (in terms of shipments) to produce the VICS receiver. A typical navigation device only has a VICS-FM receiver, but the VICS Center encourages manufacturers to produce VICS navigation devices with all three types of receivers, as this allows for more accurate and timely traffic information.
Since the establishment of the VICS Center in 1995, VICS services have been spread over 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 devices can be designed at different levels. On the hardware side, in order not to affect the user's normal listening to radio and other infotainment facilities, car navigation devices typically equip special tuner for receiving real-time traffic information. The tuner works quietly: receiving and processing traffic information along the way. This information should be left to the navigation software for further processing.
Real-time traffic information contains a large amount of content, and navigation software usually filters information as needed when processing real-time traffic information. If the user sets a destination, traffic information from the current location to the destination is very important. In-vehicle infotainment systems with navigation functions usually use the intersection enlargement map plus voice navigation tips to assist the driver in selecting the travel route. However, it is not allowed to carefully study the display content on the screen during driving. How to make the display content at a glance is an important issue in the design of navigation software. The screen processing of real-time traffic information should also be concise.
On the screen display, the simplest application of real-time traffic information is to use different colors to indicate the traffic conditions of the road. For example, roads dyed green indicate good traffic conditions, average speed is higher than 60 km/h; yellow indicates traffic is slightly blocked, average speed is higher than 30 km/h; red indicates traffic jam, and the speed is not higher than 10 km/h. The driver roughly looks at the map and knows which road to choose. On the map, you can also use a variety of icons 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 the dialog box in text form. For information that would seriously affect the expected time of arrival at the destination, requests to recalculate the path are also displayed in the form of a dialog box, and the user can decide whether to recalculate the path based on the traffic information. Further, the navigation system can also directly remind the user of the relevant road conditions in the form of voice, and ask the user whether to make a route change according to the information.
A well-designed navigation system will make full use of real-time traffic information to help travelers get to their destinations smoothly, while averaging the traffic on the road in a practical way, alleviating the pressure on road traffic.
China
As the fastest growing auto market in the world, China will have more and more cars on the road, and the pressure on road traffic will 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 advantageous for both the traveler and the traffic management department.
To establish a real-time traffic information system, we must first establish standards. In order to be in line with international standards, the choice of standards will generally be between Europe's TMC, TPEG and Japan's VICS; according to historical experience, the possibility of formulating new standards in line with China's actual situation is also very large. For example, China can fully develop a nationally unified list of locations based on standards such as TMC. The broadcast method can utilize China's existing digital television 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 group of professionally qualified information collection and editing units. These units can collect real-time road traffic information from major cities in China and submit them to the information center for processing and broadcasting.
The business model of China's real-time traffic information service should also be inclined to public services, that is, end users receive it for free. This will facilitate the popularization of the application and the mitigation of traffic pressure, and will actually reduce the government's 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 have an understanding of future new applications and are ready.
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