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Vehicular Communications for Cooperative Safety Systems

Luca Delgrossi, senior group manager of Driver Assistance & Chassis, U.S. Mercedes-Benz Research & Development

October 7, 2010

Passive safety systems, such as air bags, seat belts, and crumple zones, are the traditional cornerstones of vehicle safety. To further improve safety, however, automobile manufacturers are increasingly concerned with developing active safety systems. Many existing active systems, such as anti-lock brakes and electronic stability controls, have proved so effective they are now required on new vehicles sold in the United States.

The role of communications in active vehicle safety systems was the topic of an ITS Institute Advanced Transportation Technologies seminar held October 7. Luca Delgrossi, senior group manager of Driver Assistance & Chassis for U.S. Mercedes-Benz Research & Development, described the development of cooperative safety systems that enable vehicles to exchange safety information with other vehicles, roadside infrastructure, and (potentially) personal electronic devices.

Some cars, such as those manufactured by Mercedes-Benz, are fitted with autonomous sensors that monitor environmental conditions and reliably assess a vehicle’s surroundings. For example, these sensors can tell when a car drifts from its lane and can even provide direct safety assistance by suggesting that the driver may be too tired to continue. But these systems have a limited range and are expensive. Further, they require a direct line of sight to be effective, and they cannot detect all relevant safety data. Improving communications is the next logical step toward complementing and extending autonomous sensors’ range and effectiveness, Delgrossi said.

Delgrossi outlined the communication requirements for such a system, including the ability to function effectively at high vehicle speeds (100km/hour) and short ranges (300m is sufficient for safety), and to work within a matter of seconds. Other requirements include two-way communication between vehicles; dynamic peering (the ability to respond to rapid changes in the number of “neighbors” around a moving vehicle); and a protocol for short, well-contained messages using a common data language. Cooperative safety systems must also stand up to rigorous testing and device certification while preserving driver privacy. Finally, the systems must be tamper-resistant, durable enough to outlast a vehicle’s lifetime, and able to withstand temperature changes and vehicle vibrations.

Delgrossi also reviewed existing wireless technologies that could potentially be leveraged in cooperative safety systems. These include 5.9 GHz dedicated short-range communications (DSRC) technology, which can broadcast safety-related information (such as when approaching intersections), as well as 3G/4G data service of the type used by mobile devices. Although 3G/4G is widely used and available, there are several obstacles to deploying it in the context of vehicle safety systems: a 3G/4G network covers population areas, not specific roads (so service may not be available in certain areas), it lacks the ability to prioritize communications (so service would depend on whether users had paid their bill), and broadcast is not supported.

Other challenges for cooperative safety systems exist in the area of deployment. Policy is one such challenge; it is still uncertain which authority would regulate such systems and establish rules for their use. In addition, initial users will likely be paying for an extra feature that won’t come into use until a significant number of other cars on the road have those features. Several studies have shown that it will take at least 10 to 15 years to reach 90 percent penetration with all new models, since there are approximately 200 million registered vehicles in the United States and only 16 million new vehicles sold every year.

Rather than building cooperative safety systems into new vehicles, researchers are currently studying how to equip vehicles already on the road. The two most likely approaches are 1) partnering with automotive manufacturers to retrofit existing vehicles with DSRC equipment, or 2) using aftermarket devices (such as smart phones) to accelerate deployment.