The Case for V2V

11 May 2018
Timelapse of traffic at night in Ann Arbor, Michigan. Source: Marcin Szczepanski/Michigan Engineering.

Vehicle-to-vehicle communication, or V2V, refers to the ability of cars to wirelessly share data, such as real-time measurements of speed and position. One application is connected cruise control, which can use that data to adjust a vehicle’s speed accordingly.

University of Michigan (U-M) researchers have shown how the technology performs in a common traffic scenario, wherein a chain reaction of braking and re-accelerating happens within a line of cars. Within that context, an automated vehicle using connected cruise control was able to brake with 60 percent less G-force than would be required by a car with a human driver.

In their study, the researchers recorded scenarios where the braking got increasingly more severe while cascading along a chain of human-driven vehicles. When the speed varied between 55 mph to nearly zero, some humans decelerated heavily (up to 0.8 G), sending anything not buckled down flying toward the windshield. By contrast, the V2V-based automated driving algorithm maintained a steady speed profile that kept deceleration under 0.3 G – enough to avoid spilling a drop from a full cup of coffee.

That smoother transition translates not only to less spilled coffee but also as much as a 19 percent improvement in energy efficiency. Less energy wasted on braking also means higher mileage for a gallon of fuel or a battery pack.

"Automated cars utilizing V2V data will not only perform better, but they can also foster a friendlier environment where few safety hazards sneak into traffic and higher efficiency is possible for all cars on the road," said Gabor Orosz, an associate professor of mechanical engineering who led the research.

Experienced human drivers are often able to anticipate potential safety hazards in order to drive smoothly and stay safe. Automated cars, by contrast, are challenged by the amount of information they need to process through onboard sensors which, for instance, will respond to a cascade of braking only when the car immediately ahead hits its brakes. V2V has the potential to significantly change that equation. Human-driven cars can benefit from V2V as well. In the U-M study, they were able to save up to 7 percent energy when following the automated vehicle.

According to Orosz, major automakers such as GM, Volkswagen and Toyota are already deploying V2V devices.

"A significant amount of cars on the road will be equipped with V2V communication devices during the next few years,” he said. "Most of these cars will still be human-driven, but they will broadcast their motion information such as position, speed and acceleration. When an automated car encounters these signals on the road, it can readily pick up such V2V data and see the traffic situation beyond the reach of onboard sensors."

The research was recently published in the journal Transportation Research.

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