Vehicle-to-vehicle communication can prevent crashes

Smarter cars that talk to one another are the next step in auto safety

Consumer Reports magazine: April 2012

Wireless, vehicle-to-vehicle communication systems warn you of potential hazards.

Imagine that you’re approaching an intersection at about 30 mph, with a green traffic light beckoning you through. What you can’t see, however, is that another vehicle, coming in on the cross street, is about to run a red light. In a typical car, you would enter the intersection and most likely be slammed in the side by the other vehicle, which could seriously injure or even kill you. But in this car, a prominent red warning light flashes on the dash and an alarm blares, giving you time to hit the brakes before entering the danger zone.

That is one of several scenarios in which an ambitious new safety system being developed by the government, universities, and major automakers could help prevent an accident. The system allows cars in the same area to instantly communicate with one another over a wireless network, exchanging data about each vehicle’s speed, location, and direction of travel. With that information, the system can determine whether a crash is likely and warn drivers to brake. In more advanced designs, it can even brake the car if a driver doesn’t respond quickly enough.

In addition to vehicle-to-vehicle (V2V) communication, systems are also being developed that allow cars to communicate with roadside infrastructure, such as traffic lights, and work and school zones. Taken together, the technology is now often referred to as V2X.

To some, this may seem like a Big Brother approach to monitoring driver behavior, but according to the National Highway Traffic Safety Administration, such a system has the potential to help drivers avoid or minimize up to 80 percent of crashes involving unimpaired drivers. NHTSA’s administrator, David Strickland, calls it “the next major safety breakthrough.”

Brian Lyons, Toyota’s manager of safety and quality communications, agrees, calling it a natural evolution in automotive safety development. “The first phase was about passive systems—air bags and so on,” he says. “The second was about active safety, including electronic stability control, collision-avoidance systems, etc. The third phase will be about car-to-car communication that can dramatically reduce the number of crashes on our roads.”

Gregory D. Winfree, acting administrator of the Department of Transportation’s Research and Innovative Technology Administration, sums it up this way: “The past 50 years have been about surviving vehicle crashes; the next 50 will be about preventing them.”

Implementing connected-vehicle technology on a mass scale is still several years away, and it will need to address concerns about privacy and cybersecurity to be accepted by the public. But we’re already seeing forms of connectivity on the road that can help drivers get where they’re going
safer, faster, and more efficiently.

The safety connection

Today’s roads truly are danger zones. Each year, more than 10 million motor-vehicle crashes occur in the U.S.; in 2010, they resulted in 32,885 fatalities, according to NHTSA. That’s the lowest level since 1949, but it’s still an unacceptably high yearly tally that amounts to almost four deaths per hour. And about a fifth of those fatalities occur at intersections.

The national Centers for Disease Control and Prevention notes that motor-vehicle crashes are the leading cause of death for people 5 to 34 years old and that they amount to more than $99 billion a year in medical and lost-work costs because of injuries. Scott Belcher, president of the Intelligent Transportation Society of America, a nonprofit trade and academic organization that advocates for advanced transportation technology, says, “If you think about the impact that crashes have on the economy, transportation and mobility, and the environment, [V2X] has the potential to be a game changer.”

Roadway deaths have been reduced, thanks in part to important safety developments such as advanced air bags, well-designed vehicle structure, and electronic stability control. NHTSA says that V2X addresses a wider range of crash scenarios than any of those single technologies.

Each car transmits its data 10 times per second. That allows a car equipped with the technology to create a real-time virtual map of all vehicles in the area, individually monitoring their position, speed, and location, and calculating whether another vehicle could cause a collision with yours. If the system determines a crash is possible, it will alert the driver through real-time audible, visual, and even tactile alerts (a vibration in the seat or steering wheel), depending on the design. V2X can also alert distracted drivers to potential hazards even when they’re looking away from the road.

Building a safety network

The V2X concept is not new. In 1999, the Federal Communications Commission set aside part of the wireless spectrum for Dedicated Short Range Communications (DSRC), specifically designed to allow vehicles and related infrastructure to transfer information to each other.

‘The past 50 years have been about surviving vehicle crashes; the next 50 will be about preventing them.’—Gregory D. Winfree, U.S. Department of Transportation

NHTSA began studying connected cars with DSRC technology in 2002. In 2011, it began collaborating with eight automakers: Ford, GM, Honda, Hyundai-Kia, Mercedes-Benz, Nissan, Toyota, and Volkswagen. DSRC is being developed on an open platform, so all vehicles, regardless of brand, will be able to communicate with one another. Government officials are also working with their European counterparts to create global standards.

From August 2011 through January 2012, NHTSA conducted six driver clinics in California, Florida, Michigan, Minnesota, Texas, and Virginia, using specially equipped vehicles donated by each of the participating automakers. At each clinic, volunteers went through a series of potential crash scenarios (read “How ‘Talking’ Cars Can Protect You”) to gauge driver acceptance of the technology. Although the results of the clinics have not been made public, anecdotal comments by NHTSA experts and driver assistants at the clinics indicate that V2X is being well received.

Some of today’s cars can already provide some of the types of alerts that V2X technology gives, such as blind-spot, lane-change, and forward-collision warnings. But those alerts are currently provided through radar- and camera-based sensor systems that have a limited operating area around a vehicle. The systems are also costly and most often found on higher-end models. DSRC transmits data for about 1,000 feet around the vehicle, allowing drivers to react to vehicles around a corner or otherwise out of sight.

Because current collision-warning systems have a narrower field of view, they probably wouldn’t be able to give you advanced warning of, say, a stopped car around a bend, with the same effectiveness as a V2X system. Our auto experts note that getting a direct feed of a car’s location and speed is more accurate than having to guess that from cameras and radar.

Another benefit, they add, is that V2X technology can decrease the number of false positives that beleaguer current systems. That could be very important to win widespread acceptance of these systems.

DSRC is also relatively inexpensive to deploy, which means it can more easily be integrated into all vehicles.

The technology has already been proved to work in testing, but the biggest challenge to making it an effective safety system will be getting it deployed on a high percentage of vehicles.

“It only works if you’re equipped and everybody else around you is equipped,” says Mike Shulman, technical leader at Ford Active Safety Research and Innovation, a department of Ford Motor Company. “And how do you go from a world where nobody’s got it to a world where everybody’s got it?”

That is why a number of automakers and aftermarket companies are researching options to bring V2X technology into existing cars. GM is developing two types of mobile safety applications—a stand-alone portable transponder about the size of a portable GPS navigator and an application that uses a smart phone to receive the DSRC signal and links it to a car’s audio and video displays. Still, NHTSA experts say even a low level of vehicle penetration will provide safety benefits.

A connected campus

In August, through a grant from the Department of Transportation, the University of Michigan Transportation Research Institute will conduct the next phase of research, combining vehicle-to-vehicle and vehicle-to-infrastructure technology in a 12-month, real-life test. At the university’s Ann Arbor campus, some 2,850 vehicles will “talk” to one another.

The program will include 64 vehicles equipped with full V2X systems, provided by automakers; 300 aftermarket systems installed on the vehicles of participants; 2,500 cars outfitted with vehicle-awareness devices, which transmit the car’s location, speed, and direction; and specially equipped transit buses and trucks.

In addition to linking with one another, the vehicles will communicate with traffic lights so that the signal timing can be adjusted to increase traffic flow. Cars will also be able to interact with roadway-based systems to get, for example, a warning that a driver is going too fast for a given curve.

By 2013, after gathering all the data, NHTSA Deputy Administrator Ron Medford says the agency will assess the technology’s feasibility, reliability, and cost-effectiveness and decide whether the agency will move ahead with implementing it in vehicles or continue its research. Although not in current plans, the technology could also be designed to include pedestrians, motorcycles, and bicyclists.

What's happening now

Some regions are already using wireless systems that allow vehicles and roadside infrastructure to interact to help improve traffic and the environment. Electronic toll collection is now common.

Highways in Dallas, Minneapolis, San Diego, and Seattle are using traffic management programs that provide real-time data on travel time or lane closures on electronic signs placed over the roadways. Minnesota has used the system to reduce traffic volume by helping drivers reroute around slowdowns.

Seattle uses a traffic-signal-priority system that changes lights to allow emergency vehicles to pass through intersections, gives signal priority to buses, and synchronizes lights for better traffic flow.

Similar technology is helping truckers save fuel by letting them pass through electronic drive-by weigh stations instead of sitting and idling for long periods. Truckers can simply drive over road sensors that calculate and report the truck’s weight. In 2011, trucks were weighed electronically more than 50 million times, which helped save about 25 million gallons of diesel fuel.


Though the safety benefits of V2X technology are widely acknowledged, many people have concerns about how it will be implemented. Adrian Lund, president of the Insurance Institute for Highway Safety, says he’s excited about the technology but is concerned about the potential for too many warnings in vehicles. “I think it’s going to be difficult, in terms of parsing out the information that is relevant to the driver, so that you’re not continuously warning the driver,” he says. “Even once you’ve got the technology in cars, you still have to work out how to use it and when do you use it.” In a recent study, the IIHS found that motorists have turned off some pre-collision alerts they found annoying.

‘We want people to accept that this is a technology that’s helpful. It’s not Big Brother.’—Mike Shulman, Ford Active Safety Research and Innovation

Privacy and security issues are another concern. “We want people to accept that this is a technology that’s helpful,” says Shulman at Ford. “It’s not Big Brother that we’re putting in their vehicle.” He says that the systems will not gather vehicle identification numbers (VINs), license-plate numbers, or driver’s-license numbers and that the data are not going to be used to enforce traffic laws or give speeding tickets.

Justin Brookman, director of the Consumer Privacy Project at the Center for Democracy & Technology, says, “The concern is that once you set up a mechanism to collect data for one admittedly beneficial use, there are no intrinsic limitations on that data being collected, retained, transferred, and used for other purposes.” He cites GM, which revised its OnStar privacy standards last fall so that it could continue to collect data even after a consumer cancels the service and sell it to third parties. GM has since amended that policy.

“We’re very conscious of the issues involving privacy with this system,” says Medford at NHTSA, “and are going to work very hard to ensure that we’re not going to be collecting the kinds of data that’s going to violate the privacy of individuals and disclose that kind of information.”

The government is also focusing heavily on cybersecurity issues in an effort to make sure vehicle data can be authenticated and the system can’t be hacked.

Bottom line. Consumer Reports believes that the potential safety benefits of this technology make it worth pursuing, but adequate oversight of how the data are used is essential to ensure the privacy of drivers and to prevent abuse. And in the end, such technology is just another driving aid. Even with V2X systems in place, motorists still need to drive responsibly and stay focused on the road.

How talking cars can protect you

Vehicle-to-vehicle communication systems, commonly called V2V or V2X, are designed to prevent crashes in a number of scenarios. Federal officials have conducted several driver clinics over the past year in which public volunteers have been able to experience the technology and see how these features can help them avoid accidents:

Intersection assist. When you approach an intersection, it alerts you if another vehicle is traveling at such a speed on a cross street that it could run a red light or stop sign and hit your car in the side. This helps prevent common and often fatal T-bone accidents.

Left-turn assist. When in an intersection, it alerts you if there's not enough time to make a left-hand turn because of oncoming vehicles. This can keep you from turning even when you can't see the oncoming car.

Do-not-pass warning. When driving on a two-lane road, the system warns you when a vehicle coming in the opposite direction makes it unsafe to pass a slower-moving vehicle.

Advance warning of a vehicle braking ahead. The system emits an alert when a vehicle that's two or more cars ahead in the same lane—and possibly out of sight—hits the brakes unexpectedly. This can help prevent a rear-end collision when you're caught by surprise.

Forward-collision warning. A warning will sound if the system detects that you're traveling at a speed that could cause you to hit a slower-moving vehicle in the rear. It will also give you advance warning of a stopped vehicle in your lane that you may not see because of a vehicle in front of you or because it's around a bend in the road.

Blind-spot/lane-change warning. When traveling on a multilane road, this illuminates a warning light when a car is positioned in your blind spot. It also emits a loud beep if you activate your turn signal when it's unsafe to change lanes. V2X is more accurate than current blind-spot monitoring systems that use cameras or radar and can even warn you of a car that's accelerating into your blind zone, which conventional systems can't do.

Behind the wheel

The band of lights in Ford and Mercedes-Benz cars creates an effective warning signal.

Two Consumer Reports staffers got to experience V2X technology firsthand. Reporter Liza Barth attended one of NHTSA's driver clinics in Alameda, Calif. She drove eight V2X-equipped vehicles from different automakers to see how the technology helps in scenarios such as passing on a road when there's an oncoming car, detecting vehicles in a car's blind spot, and avoiding a driver who's running a red light. Tom Mutchler, our Auto Test Center's human-factors engineer, got to see Ford's Intelligent Intersection in Dearborn, Mich., and how vehicles can communicate with roadside infrastructure as well as other vehicles.

Overall, they both came away impressed with the effectiveness and potential safety benefits of the systems.

All of the vehicles that Barth drove received the same type of speed and location data from other vehicles. They differed only in how they alerted the driver about potential crashes. She found the display in the Ford and Mercedes-Benz cars to be the most effective. They use a bright band of lights on the dash that reflect in the windshield, coupled with a warning sound. A yellow light signals a potential hazard, and a red light warns that action, such as braking, needs to occur immediately. This is similar to the type of alert used in many of today's forward-collision warning systems. The location of the lights made it easy to see as she looked through the windshield.

Other manufacturers use an audible alert along with some kind of warning icon, short message (such as "Do not pass"), and/or graphic. General Motors and Toyota display the information above the center stack. Hyundai illustrates the warning in the center navigational display. Honda, Nissan, and Volkswagen show their visual warning in the instrument cluster, which is easier to miss.

"No matter how the visual alert is displayed, the loud beeping noise immediately gets your attention," Barth says.

In addition to audible and visual alerts, Ford's and GM's cars use vibrations in the seat cushion. It's a directional alert, so the side of the cushion that vibrates represents the side of the vehicle that is in danger. "Feeling the vibration quickly draws your attention to the hazard," Barth says.

A red-light warning from your car
Mutchler saw a demonstration of Ford's Intelligent Intersection while riding in a Ford Escape Hybrid. In addition to witnessing vehicle-to-vehicle demonstrations, he also got to see how infrastructure can aid such a system.

The intersection's traffic signal is able to transmit data to the Escape, including a detailed map of the intersection, the status of the light (red, yellow, or green), and a correction factor for the vehicle's GPS. This reduces the GPS's margin of error, allowing the system to know what lane the car is in. That is important for intersections with turn arrows or other lane-specific signals.

With the data, a car can warn a driver who is about to run a red light. Ford's engineers demonstrated this as they drove toward the intersection without braking. "Red light!" announced the Escape, and a bright strip of lights on the dash flashed, prompting the driver to screech to a stop.

The infrastructure demands of a smart intersection are modest—just the transmitter, a GPS antenna, and a data feed from the signal control. There's no need to dig up the roadway. The transmitter can also provide map information for multiple stop-sign intersections in the same area. Similar to the red-light experience, the Escape warned the driver when he was about to go through a stop sign at multiple adjacent intersections.

By the numbers

1.6 million
Approximate number of rear-end crashes in the U.S. each year.

The number of side crashes that occur at intersections every year.

Annual crashes caused by cars changing lanes or drifting in a lane.
Editor's Note:

A version of this article appeared in the April 2012 issue of Consumer Reports magazine with the headline "Stopping Crashes With Smarter Cars."

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