MIT Researchers Test Nascent Vehicle-to-Vehicle Communication Scheme

Congestion-smoothing experiment highlights opportunities for smartphone manufacturers, automakers and cities.
By Mary Catherine O'Connor

RoadRunner addresses both hurdles by relying on radios that would be embedded into drivers' smartphones—and eventually directly into the cars—and communicate with each other, forming ad hoc networks that would limit the number of cars entering a specific stretch of highway at any given time. They do this by directing the drivers away from roadways that are already full, using turn-by-turn directions given audibly.

Rather than charging a toll as a driver enters a congestion-controlled road, the RoadRunner system uses tokens that allow only a set number of vehicles onto the road at any one time. The system works like this: When a car is nearing the congestion-controlled roadway, its radio pings the RoadRunner software over a cellular network and requests an available token. If one is available, RoadRunner assigns that token to the car. If no tokens are available, the software routes the car away from the congestion-controlled road. If the driver disregards these directions and continues onto that road, RoadRunner, using the cellular connection, issues the driver a penality—which would be a fine higher than the cost of a token, thus acting as a disincentive to ignore routing directions again in the future.

Gao and Peh's approach would also address another form of congestion: broadband cellular traffic. "There is not a lot of bandwidth left," Gao explains. "If you brought millions of [drivers] onto the network, it would overload it" due to the intensive computation required to constantly monitor how many cars have entered or exited a monitored roadway. Rather than having to eat up broadband by having each car constantly send its GPS coordinates to a cloud-based server via a cellular connection, however, the program has the vehicles use the 802.11p communication standard to transmit their location and unique identifier to each other over an ad hoc network. The IEEE developed 802.11p to enable vehicle-to-vehicle or vehicle-to-infrastructure communication. The latter would be used for such things as electronic tolling or safety systems wherein cars can be linked to streetlights or other infrastructure. The protocol enables faster data transmissions, over a longer range (around 6 megabits per second and a range of up 1,000 feet) compared with conventional Wi-Fi.

RoadRunner uses a cellular connection only to manage the issuance of available tokens, or to issue a fine to a driver who disregards instructions to avoid a congestion-controlled zone.

Following software simulations, the team tested RoadRunner in a live scenario in Cambridge. Each driver's phone was linked, via a USB cable, to a Cohda Wireless 802.11p radio unit. These radios allowed RoadRunner to monitor the location and number of cars inside the region that had been designated for congestion control. Once the software determined that the maximum number of tokens had been issued, it would direct the next driver headed toward that area to turn away from it, just as it had done in the software simulation.

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