Networked cars put to traffic jam test in Germany

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Instrument panel displays under test by the simTD project in Germany will warn drivers of oncoming emergency vehicles and their lanes.

Connected-car technology, if done right, would be safe, smart, and affordable. Vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications can alert drivers—and each other—of unseen road hazards and traffic jams. But before cars can be linked in wireless networks, engineers must show that the collective V2X technologies operate with bulletproof reliability. After all, fully verified safety is the only way to earn motorists’ trust.

One significant remaining challenge to V2X technology, for example, is traffic congestion. What if every vehicle in a jam reported in simultaneously? Would the flood of signals overload the network? The German auto industry and road ministries are planning to find out during the coming spring in a large-scale test of the technology. Evaluation will take place amid the real road traffic of the some 5 million plus inhabitants of the Frankfurt-Rhine-Main area of the state of Hesse, the country’s second largest metropolitan area.

The simTD project (Safe and Intelligent Mobility Field Test Germany) results from collaboration among 18 project partners including major German automakers; suppliers Bosch and Continental; German Telekom; several research institutions and universities; as well as three government ministries.

A 120-vehicle test fleet will begin six or seven months of field trials in the spring, said Christian Weiß, the project coordinator and manager of cooperative systems for the research and advanced development department at Daimler AG. Right now several passenger car models—Audi A4, BMW X1, Mercedes C-class, Ford S-max, Opel Insignia, and Volkswagen Passat—are being fitted to communicate wirelessly with each other and with sensors in road beds and infrastructure via short-range V2X links.

The test zone includes hundreds of ITS roadside stations installed by the Hessian traffic center (VZH) and the Integrated Traffic Management Center Frankfurt (IGLZ) that will enable simTD test fleet vehicle to exchange data with traffic lights, road signs, and traffic control centers.

Next step in auto safety

“We are convinced that car-to-X communication represents an important step on the way to accident-free driving,” Weiß noted. European research generally coincides with a NHTSA report that in the U.S. four-fifths of vehicle-on-vehicle accidents involving unimpaired drivers could possibly be prevented if vehicles just talked to one another.

“Foremost for us is the safety benefit,” he explained. V2X provides the basis for all kinds of warnings of dangerous road conditions, traffic jams, construction sites and obstacles, and weather dangers. Crucially it can inform drivers early enough to allow them to adapt, to change their behaviors, to avoid hazards. The simTD system is to alert drivers of approaching emergency vehicles, display to drivers the right lane to take for the next turn, or advise on the optimum speed to catch a wave of green lights.

“Also it’s the only sensor that can let you know that there is a hard-braking vehicle right in front of that big truck that’s just ahead,” Weiß said. Though some radars try to pass under vehicles, they don’t have the same potential, he said. “No other sensor can reliably warn you of what’s going on just ahead of a truck."

Enhanced traffic management

Traffic efficiency should improve as vehicles transmit information on traffic conditions to a control station, which can then predict and manage traffic developments, Weiß continued. “V2X technology would allow operators to get a current view of the state of the traffic.”

Today, magnetic induction loops buried in the roadway or overhead video cameras can count traffic flow at hot spots, but they are expensive and few. Operators, he explained, have to guess what’s happening in between sensors.

“V2X provides an accurate view of what’s happening on the road network, which allows you to adapt your traffic management strategy to improve capacity utilization, so as to avoid having to build new roads, which is a huge overall challenge.” Managers might alter the speeds on variable traffic signs to boost safety or traffic flow.

And then there is the opportunity to piggy-back all kinds of other local services onto the existing network, he noted. Concierge-level mobile services, such as parking space reservations in garages, might soon follow initial installation, for instance.

Short-range wireless

Whatever their name, V2V, V2I, V2X, or Car2X networks are based on heartbeat-like vehicle-status signals that transfer data over short ranges between transponders on vehicles and infrastructure. The simTD’s ITS G5 wireless technology, which is tailored to automotive applications, is based on the familiar WLAN standard. The hybrid system meshes the workings of the specially developed wireless vehicle communication standard 802.11p and UMTS mobile phone technology as well as ad hoc networking. This approach was chosen as the most promising because of its potential for favorable economies of scale, he said.

For most applications, the messages are short, but they have to be delivered very rapidly in the tens of microseconds range. The signals only need to travel a maximum of 500 m (1640 ft). For longer distances, the system uses multihopping technology. The wireless message either jumps to a roadside unit, which passes it on to following and oncoming vehicles. These then pass useful messages to others that they meet.

Weiß said that he expected to start the "pre-experiments" to tune the trial's evaluation system as soon as the instrumented fleet expands. NEC Laboratories Europe recently delivered the key components of the V2X network software to the simTD partners that enables real-time dissemination of data for traffic safety and traffic efficiency as well as infotainment applications.

Real-world tests

Specialists from the Technical University of Munich are managing the simTD field test and will evaluate the prodigious amounts of data it should generate. Teamed with researchers from Wurzburg University, they are simulating the impact the introduction of the technology would have on traffic if the proportion of cars that were equipped grew enough.

“We have a huge test region, as large as any yet tested, that includes all varieties of infrastructure, all major road types—an airport, a trade fair, high-traffic areas,” Weiß said. Analysts will determine how drivers adapt to the technology and establish how successful it is on highway, rural, and urban roads.

“We need to test to [know] what happens if you have a four-lane highway with hundreds of vehicles in traffic transmitting at the same time,” said the simTD project coordinator. "The communications must be ensured, even under high load. Scalability is the key," he emphasized, pointing out the costly investment in infrastructure and vehicle technology such a nationwide effort will require. “Plus we don’t want to have to update it every minute.”

The $92 million (€71 million) project is backed by public and private funding, including support from Germany’s Federal Ministry of Economics and Technology, the Federal Ministry of Education and Research, and the Federal Ministry of Transport, Building, and Urban Development.


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