Vehicular networking and road weather services are advancing traffic safety in Finland, say Timo Sukuvaara, Pertti Nurmi, Evgeny Atlaskin, Kari Mäenpää and Riika Ylitalo.
Vehicle-to-vehicle communication (V2V) and between vehicles and roadside infrastructure (V2I) has been widely studied as an enabler of enhancements in traffic safety and efficiency. In recent studies the role of road weather information and vehicle-oriented observations have been recognized as key elements in the safety enhancements. These elements form the major objectives in the European Eureka/Celtic Plus project CoMoSeF (Co-operative Mobility Services of the Future), creating co-operative mobility solutions (including devices and applications) feasible for large-scale deployment.
In practice this means communication systems between vehicles as well as between vehicles and infrastructure employing interactive testing of safety and weather information exchange services. FMI (Finnish Meteorological Institute) has an essential role in the project as a professional weather service provider. FMI is especially focused on approaches to employ CoMoSef vehicular networking entities to provide route weather information for vehicles bypassing a combined Road Weather Station (RWS)/Road Side Unit (RSU). Route weather is a special type of weather service tailored for dedicated road stretches and is based on a road weather model and data collected from local RWS and from vehicles themselves.
CoMoSeF creates a co-operative communication system between vehicles and vehicles and infrastructure. The aim is not only to service vehicles, but also to exploit vehicle-originated data. Similarly, road-side units are not just serving the vehicles as connectivity points, but they also host RWS capabilities to provide additional data for the services. In some cases it may even be more important to have RWS capabilities while compromising the wireless vehicular communications.
Intelligent wireless traffic service platforms with new types of vehicular services for improved traffic safety have been widely studied, among them in the WiSafeCar project that preceded CoMoSeF. CoMoSeF itself brings existing and emerging sensors, services and communication solutions closer to market and creates the business models needed. One issue is vehicle-bus (eg CAN) as a data source. Back-end applications, road side units and road sensors are employed to support drivers’ decisions. An RWS stores and maintains information collected from the near environment of ITS Station in its vicinity, based on geo-casting delivery software and a Local Dynamic Map database.
The CoMoSef project development focuses on nomadic devices with cost-effective services, which are easy to implement and deploy in all vehicles. The main envisioned services are the aforementioned weather-related services, warning of poor sections, speeding warnings, safety margin warnings, friction monitoring and forecasting, fog vision detection driver visibility improvement and driver behavior detection, respectively. For the demonstration purposes the idea is to develop and deploy “Road Weather Testbeds” to test wireless networks and communications in public with advanced communication applications. In the demonstrations conducted and yet to come, our goal is to use the local RWS data to generate road weather services and build simple communication procedures around the RWS location to deliver the data to the vehicles.
STATION TO STATION
In order to fulfill these tasks, FMI has constructed a special RWS nearby to its facilities in Sodankylä in northern Finland. The station is equipped with up-to-date road weather measurement instrumentation, compatible (but not limited to) with the equipment expected to also be available in the demonstration site’s own, permanent and locally owned RWS. The procedure is to design, develop and test both the local road weather service generation and the service data delivery between RWS and vehicles.
The CoMoSef project will use the IEEE 802.11p standard as the primary communication entity, with supporting LTE, Wi-Fi (IEEE 802.11g/n) and cellular networking (3G) as the alternative communication methods if IEEE 802.11p based system or equipment is not available. In the Sodankylä RWS there is the IEEE 802.11p primary communication system, supplemented with parallel Wi-Fi communication and alternative 3G communication, respectively. In the Sodankylä combined RWS/RSU scenario the focus is on V2I communication.
The vehicle bypassing the combined Road Weather Station and Road Side Unit (RWS/RSU) is supplemented wirelessly and automatically with up-to-date road weather data and services, and also potentially available vehicle-oriented measurement data are delivered upwards. The local server in RWS/RSU hosts the station operations. It is linked with a NEC Linkbird-MX modem for IEEE 802.11p communications but has also an internal Wi-Fi modem. Both of these communication channels are actively seeking the bypassing vehicle communication systems. The local server is also gathering measurement data from two different measurement entities, Vaisala Rosa road weather measurement system and FMI weather stationmeasurements, respectively. The data from these sources, together with possible vehicle-oriented data are sorted and further delivered to FMI local facilities through a 3G communication link. The advanced services are developed in FMI facilities and delivered back to the RWS/RSU to be further delivered to vehicles. The same software entity maintains the data delivery between RWS and vehicles and RWS and FMI site, while gathering and updating the local weather data from the RWS/RSU.
FOREWARNED IS FOREARMED
The main advantage of RWS/RSU is the exploitation of local RWS and vehicle data for up-to-date weather services. Adverse road weather conditions like icy roads, fog, heavy precipitation and strong winds can cause accidents, traffic congestions and delays. Forecasting and weather information systems and applications have been actively developed by FMI, since the Finnish wintertime weather conditions can be extremely demanding. A state-of-the-art operational real-time road weather forecast system covering the whole of Finland is being run operationally by FMI to serve traffic safety needs.
FMI will implement and further develop road weather systems for the test sites. The basis for road weather analysis and forecasting is a 3-dimensional atmospheric Numerical Weather Prediction (NWP) model which is based on physical-mathematical equations describing the state of the atmosphere. Such models simulate the major physical processes behind different weather phenomena and produce explicit forecasts of various meteorological quantities. The models can also produce ”post-processed” output variables defining different road conditions like dry, wet, frosty, snowy, or icy conditions. The forecast domain of the model covers the whole of Europe and the idea is to “downscale” it to test sites. To produce road weather forecasts along individual road stretches we need to tackle higher spatial and time resolutions than presently available. To accomplish this we employ a method of dividing road stretches into a number of segments and performing model simulations for each segment.
Depending on available computer resources, the scale of a road segment can vary from a few kilometers down to meter-scale. Local road weather observations are useful to initialize the road weather model, thus resulting in more accurate forecasts. The number of deployed road weather stations (at the test sites) is, however, limited hindering a detailed analysis of the meteorological conditions along the roads. The analysis of the meteorological conditions will be performed either by a data assimilation system incorporated into the NWP model, or through a high spatial and time resolution local analysis scheme that is presently under operational exploitation at FMI.
The state of the road surface depends on traffic intensity and volume. At near-surface temperatures slightly below 0ºC the tyre friction and the heat flux emanating from the vehicle can cause surface ice to melt and thus change the slipperiness conditions of the road surface. Therefore, taking into account the traffic intensity and volume is very important in the computations of the road surface temperature and water phase changes. Traffic will be taken into account by the model in places where such information is available.
Road maintenance actions, such as spreading of reagents and snow ploughing can substantially alter the state of the road surface. It would, therefore, be very important to take into account the road maintenance scheduling and the resulting actions in order to be able to initialize the model with proper input data and to produce forecasts with higher accuracy. Unfortunately, the information on road maintenance actions is typically not available to weather services. Being available such information could be included in the model initialization.
The main focus of this work is on the architecture for a V2V and V2I access network. The architecture is on the path for demonstration platforms and evaluation. A set of pilot services focusing on accident warnings and road weather data reflect the general type of vehicular networking services employing the platform. The resulting IEEE 802.11p communication architecture with 3G and LTE communication and embedded services is the major innovation. Even if the commercial deployment of the architecture remains to be seen, it introduces a considerable outlook of a hybrid communication design for the operative vehicular networking environment.
Timo Sukuvaara, Pertti Nurmi, Evgeny Atlaskin, Kari Mäenpää and Riika Ylitalo all work for the Finnish Meteorological Institute