Cooperative ITS safety-related services are based on a connectionless mobile communication network work. Compared to traditional connected services known from smartphones they distinguish with respect to basic principles, characteristics, service classes and user groups as well as related business models. The CAR 2 CAR Communication Consortium publishes a set of frequently asked questions providing background information, explaining the main points of interest also covering the cooperative technologies, features and differences. By nature the FAQs are not complete and will be therefore updated from time to time.  

FAQs – Frequently asked Questions

 When will drivers benefit from Car2X on European roads?The Day 1 Car2X safety applications have been developed and standardised during the last decade. As of 2019 the first mass-market vehicles are equipped with Car2X safety function as standard equipment. Further vehicle brands follow. As of 2020 European road operators offer the roadworks warning as one of the first services in daily operation complemented by a bundle of further infrastructure enabled Day 1 services. By this already first drivers benefit from Car2X and service quality will improve steadily with increasing market penetration. 
 What are the advantages of Car2X for drivers?Car2X is specially designed to improve road safety free of charge and by this supports assistance of drivers and automation of vehicles. In case of a danger ahead the driver will be warned by Car2X in time and supported to avoid the critical situation. Volkswagen Golf 8 has received the Euro NCAP Advanced Award 2020 for the implemented Local Hazard Warning system that uses ad-hoc short-range communication between cars, and between the car and its surroundings, to give drivers an early warning of safety hazards.
 What are the advantages of Car2X for road operators?Road operators are in charge of managing traffic flow and of operating their road network and its maintenance. Beyond gantries, variable message signs and traffic lights Car2X offers the opportunity to interact with cooperative vehicles to improve road safety and road capacity. By locally providing cooperative information road operators benefit from market driven improvements of driver assistance systems and automated driving functions of cooperative vehicles. Furthermore, cooperative vehicle data very much improves the statistical probe traffic information enabling further innovations for traffic management and maintenance of roads and bridges.
 Is Car2X tamper-proof and takes care of the drivers’ privacy?For improving road safety local short-term tracking of the road users in the vicinity of the ego-vehicle is required. Privacy by design has been applied to the Car2X systems for ensuring the privacy of the driver. All identifiers of the messages sent out change over time and travel phase following an optimised privacy strategy avoiding long-term tracking. Furthermore, the frequency and the amount of shared data is dynamically triggered by the driving situation following the principle of data economy. The Car2X design also considers threat analysis for compromising and manipulating message sets and/or ITS stations. As a consequence, all message sets are signed with an electronic signature avoiding manipulation, replay and misuse.
 Why are Day 1 message sets not encrypted?The Day 1 message sets like Cooperative Awareness Message (CAM) and Decentralised Environmental Notification Message (DENM) are safety related messages, which need to be understood and processed in real time by all other cooperative road participants in the vicinity of the sending vehicle. Due to this fact encryption of these messages would not provide any advantages on privacy, but needlessly waste computation power and by this delay well adapted safety measures in critical situations. Instead of encrypting messages, all message sets are signed by the sender and verified by the receiver. In this way it is ensured that all data is reliable and not susceptible to manipulation by third parties without the need for encryption / hiding the data.
 What are the special features of C-ITS compared to other ITS services?Cooperative Intelligent Transport Systems (C-ITS) refers to transport systems, where the cooperation between two or more ITS sub-systems (personal, vehicle, roadside and central) enables and provides an ITS service that offers better quality and an enhanced service level, compared to the same ITS service provided by only one of the ITS sub-systems.
 Which technologies enable C-ITS? Suitable technologies depend on the applications to be realised. Avoiding accidents by fore-sighted cooperative driving and safety applications are primarily a tactical issue requiring the sharing of information, perception, awareness and intentions between the road users in their vicinity and with the local road infrastructure. The ad-hoc short-range communication of Car2X systems focuses on this class of safety related applications. Applications like route planning and navigation focusing on the strategical and planning level as well as remote tele-driving require wide area communication. For covering all C-ITS applications a hybrid approach is required. Here the proven short-range communication Car2X (ITS-G5) can be complemented with other mature communications like cellular systems (3G, 4G, 5G) and broadcast systems (RDS-TMC, DAB+). 
 Why is short-range communication well suited for improving road safety?Improving road safety targets on avoiding accidents between road participants. The probability of an accident strongly depends on the local traffic situation. Fore-sighted driving strategies considering the current local traffic situation in the vicinity of a vehicle are well suited to contribute to avoiding critical traffic situations and to take ad-hoc counteractions aiming on the avoidance of remaining potential accidents. The quality of service of the connectionless short-range broadcast communication improves the closer the road participants approach each other and by this supports individual ad-hoc actions for mitigating the local critical traffic situations. Furthermore, this physical principal of short-range communication ensures functioning anywhere at any time where cooperative road participants come closer to each other avoiding any local dead spot.
 How does cooperative automated driving benefit from C-ITS?For sure safe autonomous driving can be realised based on vehicular sensors only without any communication to other road participants or road infrastructure. However, such an approach limits driving comfort and reduces road capacity. The local information exchange between cooperative road users and with road infrastructure based on short-range communication enables enhancements of fore-sighted driving. By this road safety, traffic efficiency and driving comfort can be improved significantly. Tele-driving might be required as fallback solution for automated driving vehicles to overcome unusual situations which cannot be handled by the automated vehicle itself. However, this fallback solution requires a reliable mobile wide-area communication like cellular (4G, 5G) providing sufficient bandwidth without any dead spot along the roads.
 Can cellular communication serve cooperative Day 1 use cases?As a basic principle mobile communication via cellular network requires a contract with a mobile network operator and is subject to costs. For serving Day 1 use cases by cellular network vehicles communicate to all other vehicles in their vicinity always by sending their information via the local base station to the backbone system of the cellular network which links the information back to each of the vehicles of interest. Edge computing at the base station can shorten this communication and reduces resulting delays. However, in case of a critical traffic situation the communication channel of the base station might become overloaded compromising the reliability of the (multi-point to multi-point) service. Other communication issues result from cases where the communicating vehicles belong to different mobile network operators especially when roaming is required. Also, possible dead spots along the roads might limit the quality of service of cellular communication for cooperative safety related use cases. Because of these reasons short-range connectionless broadcast V2X communication (point to multi-point) between the local cooperative road participants is more suitable for safety related use cases.
 What makes Car2X superior compared to other technologies?Car2X systems use the connectionless short-range communication ETSI ITS-G5 based on the automotive designed WLANp standard called IEEE 802.11p. Car2X is a locally self-organising ad-hoc network, performing everywhere at any time where cooperative units come closer to each other. The ad-hoc communication fits quite well with the stochastic channel usage caused by varying frequency and data size of the messages. The data transmission is for free (no subscription required), offers required robustness and reliability, quality of service and fulfils functional safety requirements. It operates independent of third-party commercial driven decisions and of other commercial communication networks. The NGV successor standard called IEEE 802.11bd is designed to offer a seamless evolution of the radio technology which ensures efficient use of the allocated spectrum, continuous operation of implemented services and by this safeguarding previous taken investments.
 Does the Car2X communication fit for passenger cars only?The short-range Car2X communication can be used for all kinds of cooperative vehicles like passenger cars, trucks, working machines, agriculture machines as well as motorcycles, other powered-two/three-wheelers including pedelecs, e-bikes and other vulnerable road users. For the later one’s power supply and accurate positioning highlight the main technical challenges to be solved for enabling reliable safety related applications.
 Can the communication technologies LTE-V2X, C-V2X and Car2X understand and talk to each other?The mature Car2X communication technology has been especially designed for the stochastic message exchange with respect to frequency and size of the safety related messages. The robust ad-hoc short-range data exchange between vehicles and with road infrastructure performs anywhere at any time and offers seamless evolution with the NGV successor radio technology under development. This allows efficient usage of the allocated ITS spectrum and safeguards taken investments. Beginning 2020 first LTE-V2X radios entered the market. Unfortunately, LTE-V2X is not interoperable with Car2X requiring its operation in a separate channel. The same holds to its successor C-V2X which is neither interoperable with Car2X nor with LTE-V2X. The direct communication of LTE-V2X and C-V2X can coexist in the same channel but are not able to communicate to each other.
 Can Car2X be used also for other domains than road traffic?The Car2X radio is based on the IEEE 802.11p WLANp standard which has been especially designed to fulfil automotive requirements in real traffic scenarios and to ensure data communication at high speeds up to 500 km/h. These features enable the application of the radio technology also for other domains like railway. Several Rail2X projects have successfully proven smart services based on WLANp communication like train to infrastructure, train to railway crossings, train to railway station. 
 How is European C-ITS standardisation organised?The CAR 2 CAR Communication Consortium provides an industry-wide platform to harmonise the technical details from R&D projects and to forward harmonised white papers and to contribute to the European standardisation in ETSI. For this the CAR 2 CAR Communication Consortium has established a close liaison with ETSI to foster the exchange of C-ITS standardisation and technology.
 How is worldwide C-ITS standardisation enhanced?The CAR 2 CAR Communication Consortium supports initiatives of the European Commission like C-ITS Platform and its successor CCAM Platform. Close liaisons have been established among others with the Amsterdam Group, C-Roads Platform, European Commission, ETSI and other relevant Standardisation Organisations like CEN/ISO, IEEE and SAE to support the worldwide harmonisation.
The worldwide standardisation itself is performed by the Standardisation Organisations in particular ETSI TC ITS.
 In which frequency band is Car2X operated? Around the world the ITS frequency band has been allocated in the 5.9 GHz spectrum. In Europe the ECC decisions (08)01[ER-65] and EC decision 2008/671/EC build the legal basis for the operation of an ITS G5 system in the spectrum band 5855MHz to 5905MHz split into 5 channels with 10MHz. Due to overlapping with the SRD band the lower 2 channels from 5855MHz to 5875MHz are for traffic efficiency application whereas the 3 channels from 5875MHz to 5905MHz are allocated to traffic safety applications.
 Does the Car2X operation interfere with other ITS services?The CAR 2 CAR Communication Consortium and Car2X are committed to the provision of interference mitigation with other existing communication systems used in neighboured channels. The tolling system operated in the band 5795MHz to 5815MHz has to be protected by a significantly reduced spurious emission level of a Car2X system in that band or equivalent mechanisms like the reduction of the duty cycle. Urban Rail systems are operated in the band 5915MHz to 5925MHz. ETSI is working on sharing mechanisms between Car2X and Urban Rail systems. Urban Rail systems have priority over any kind of road ITS systems in this band.
 When will the Car2X functions come into series production?First OEMs already equip mass-market cars with Car2X Day 1 functions as standard equipment as off 2019. The CAR 2 CAR Communication Consortium expects to have a noteworthy share of equipped cars on the roads in 2020+.
 How will the services of competitors distinguish from each other?Even the received data and the basic Car2X system design are the same the integration in the car and the presentation in the display (HMI) will be individual and brand specific.
 Will there be retrofit solutions?No, for safety applications the integration into the car does not allow that in the moment.
 How can market penetration be enforced?The more applications and benefits the Car2X system can offer the more vehicles will be equipped. The more brands, markets and infrastructure are involved, the faster the customers see the Car2X benefits. Therefore, the integrated approach of considering the variety of Car2Car and Car2Infrastructure use cases is the appropriate course of action.
 What is the role of the CAR 2 CAR Communication Consortium?

The mission and the objectives of the CAR 2 CAR Communication Consortium are improving road safety and road efficiency and supporting automation based on cooperative Car2X systems. Here the Consortium acts:

  • To enable and to guide the development of cooperative safety applications by specifying, prototyping and demonstrating the Car2X system
  • To create and establish an open European industry profile for Car2X systems based on ad-hoc WLANp components and to guarantee European-wide inter-vehicle interoperability and backwards compatibility 
  • To promote the allocation of a royalty free European wide exclusive 5.9 GHz ITS frequency band for Car2X applications
  • To contribute to international standardisation of cooperative Car2X systems especially in cooperation with ETSI TC ITS
  • To push the harmonisation of Car2X standards worldwide
  • To cooperate with road infrastructure for aligning automotive Car2I / I2Car developments and deployments
  • To develop realistic deployment strategies and business framework to speed-up the market penetration
 Will already implemented Day 1 services stay operational when new Day 2+ services will be rolled out?The Car2X system is designed to offer interoperability across borders and brands. All future services have to fulfil the interoperability and backwards compatibility requirements. This ensures the further operation and service of older Car2X systems in the field without any required update or upgrade. In line with these requirements, the NGV successor standard of the radio system allows flexible and seamless evolution, which ensures efficient use of the allocated spectrum, continuous operation of implemented services and by this safeguarding of investments taken.
 What comes next after the first Day 1 services being implemented on European roads?The phases of the roadmap build on top of each other. The initial Day 1 phase focuses on cooperative awareness and decentralised notification services involving cooperative vehicles and road infrastructure. With increasing market penetration Day 2 services are enabled improving and complementing the Day 1 services and offering collective perception services. Having these services in the field Day 3+ focuses on real cooperation by sharing intentions and coordination data. Cooperative Day 3 assisted and automated vehicles will share their trajectory and manoeuvre planning, support negotiation and coordination as well as active VRU advertisement.
Use Cases
 Which Day 1 use cases are offered by Car2X? The first cooperative vehicles offer cooperative awareness and decentralised notification services providing valuable user benefits already at low penetration rates. These Day 1 services comprise use cases like local hazard warning (e.g. broken-down vehicle, hard braking, end of traffic jam, slippery road), emergency vehicle warning, work zone warning, motorcycle indication up to cooperative ACC. Also, traffic light information and prioritisation of public transport and emergency vehicles are of high interest and are already being enabled by several front-runner cities.
 Can emergency vehicles benefit from Car2X already today?Already the Car2X Day 1 implementations allow cooperative emergency vehicles to use services like emergency vehicle warning, traffic light prioritisation or stationary vehicle warning. Next deployment phases will complement further sophisticated customised services.
 What is about public transport in cities? Which advantages does Car2X offer for public transport?Generally public transport vehicles benefit from the Car2X safety features as any other vehicles equipped with a Car2X system. Furthermore, public transport vehicles are enabled to request prioritisation at intersections signalised with cooperative traffic lights. Also, the stationary vehicle warning might be used at bus stops to safeguard the passengers during (de-)boarding.
 Can Car2X support truck platooning?The deployed Day 1 services provide improved safety also for platoons. Today the brand independent truck platooning is still under development and Car2X is used for all tests on the European roads. New messages and control systems are under development enabling the automation of all platooning processes. Having tested and harmonised the new message sets in R&D projects their standardisation is required. Brand independent truck platooning is expected to be part of Day 2 deployment phase.
 Does Car2X also integrate agriculture vehicles and construction machines?Day 1 Car2X can be used by agriculture vehicles too for further improving road safety.  Agriculture vehicles are special vehicles with unusual dimensions and behaviour for most of the drivers of other vehicles. Also, agriculture vehicles benefit from the safety features already provided today by Day 1 Car2X systems. Avoiding accidents saves lives and directly pays-off during agricultural campaigns. Further Car2X road and on-field applications are under development.
 Does Car2X support the Green Deal for Europe policy?Car2X is designed to enable fore-sighted driving, to contribute to improving road safety and road efficiency and to support automation. Already Day 1 enables fore-sighted driving. Smooth travelling avoids unnecessary acceleration and deceleration, reduces the energy consumption, related emissions and particulates. Next deployment phases will support further use cases providing enhanced Green Deal for Europe benefits.
 Which Day 1 infrastructure-based services are offered to the road participants?The European C-Roads pilots have harmonised and tested the Day 1 infrastructure-based use cases for ensuring European-wide interoperability. As of 2020 the following services will be transferred into operation. Road Works Warning provides warnings at day building sites and moving construction sites. Hazardous Locations Notification informs about use cases like end of traffic jam or slippery road. In Vehicle Signage provides information about speed limits, no passing and other relevant traffic signs. For cities the signalised intersection is of high interest offering use cases like green light optimal speed advisory (GLOSA) or traffic light prioritisation e.g. for public transport and emergency vehicles.
 How will the Car2X system protect vulnerable road users (VRUs)?Infrastructure sensors as well as sensors of cooperative vehicles can be used for detecting VRUs and other non-equipped road users. By sharing their object information hidden objects can be recognised. Collective perception is most suited to protect VRUs and road safety is expected to be improved significantly by this Day 2 service. Having solved the technical challenges of power and accurate positioning of VRUs they shall become directly involved in the cooperative Car2X system allowing active VRU advertisement. Other technical concepts for protecting VRU based on V2X equipped smartphones face many technical challenges like power consumption, accurate positioning, data protection and misbehaviour detection. Furthermore, the safety impact is limited since not all VRUs will actively use such a smartphone concept always (e.g. kids). Therefore, based on today’s available ITS-G5 technology the cooperation with intelligent road infrastructure enables most promising protection to all VRUs in sensitive areas.
 How will extended weather information help automated driving vehicle to drive more precise and saver?Even the most sophisticated automated or autonomous vehicle can only sense its immediate surrounding similar to a human driver. If the road condition changes rapidly there is a high likelihood that a vehicle travelling too fast might lose its traction momentarily. Traction control will of course allow some measure of mitigation of the hazard created by weather conditions, but it is only applicable within the limited sensorial range of the vehicle. However of course by communicating detected areas of hazards to other cooperative vehicles a swarm mentality can be envisaged to alert all road users as required. The solution promoted on extended weather information uses the network of cooperative ITS sensors and stations to create a consistent and accurate view of weather conditions across the entire road network that will form the basis of forewarning any vehicle that it is about to approach a hazardous location.
 How will Traffic Management support cooperative vehicles?Infrastructure Traffic Management Center systems (TMC) use cooperative vehicles to get a more precise overview of the current traffic situation by using ITS-G5 messages at all areas. For informing cooperative vehicles TMC systems use short- and long-range communication. Road Authorities have the sovereign responsibility for the Traffic Management and can use control processes and real time RSUs messages for sending information and warnings to the vehicles on their roads. By this the area wide traffic management (advanced traffic management) can influence the traffic flow on the roads and contributes to making road traffic safer and more efficient.
 Can the Car2X system be used for other vehicle solution like trains, trams, or tubes? Rail2X is using the same ITS-G5 application as cooperative vehicles. Use cases at infrastructure are used in a similar way for SPATEM / MAPEM / GLOSA / DENM / IVI. ITS-G5 is designed for automotive safety related applications and can be used for many other vehicle solutions. Several projects successfully have shown the high performance of the ITS-G5 radio based on IEEE802.11p (WLANp).