How Traffic Jam Assistance Systems Work

Trust the Car, Not Your Instincts
Radar sensors and a camera give input to the system, which automatically controls the speed, the brakes and the steering in order to follow the vehicle in front.
Radar sensors and a camera give input to the system, which automatically controls the speed, the brakes and the steering in order to follow the vehicle in front.
Courtesy of Volvo Car Group

Volvo, eager to determine if the traffic jam assistance system had more widespread potential, ran a few tests to see if it actually could alleviate traffic jams.

The SARTRE (Safe Road Trains for the Environment) project sounds like it was researching the safety of the super-long semitrailer trucks that are known as "road trains" in some areas (namely Australia). But in Volvo-speak, a road train is a pre-coordinated stream of cars that use advanced cruise control-type technologies to follow each other in a planned path of travel, with established safe following distances between each vehicle. A touch screen lets the driver input commands, such as joining or exiting the road train, or communicating with other vehicles in the road train, but beyond that, the driver of each individual car in the road train is largely relieved of the burden of driving.

The technology used in the SARTRE program, similar to the suite of tools that makes up traffic jam assist, was already in the cars used for the test -- it was composed of other safety features that have (in comparison) stood the test of time, like adaptive cruise control, blind spot monitoring and park assist. Since the cars' onboard diagnostics are so sensitive and precise, Volvo says that, at times, the road train traveled safely with less than 13 feet (3.9 meters) from bumper to bumper.

Volvo sees this technology as a plausible alternative to public transportation, providing a combination of an individual's own comfort with automated travel. It also offers moderate energy savings over regular driving, and takes up less space on the road than the same number of vehicles would occupy if each were driving independently. However, it's not as simple as just joining a line of cars that happens to be heading in the same direction. The road train must be scheduled and coordinated ahead of time, and led by a professional driver. There are too many questions that need to be answered, such as how well a road train can cope with an unforeseen road disaster. And, so far, all of Volvo's tests have been focused on potential for the European market -- whether or not this will fly in the United States is completely unknown.

There are reasons other than the home-court advantage that convinced Volvo to test in Europe. From an automaker's perspective, the United States' safety regulations are an absolute mess [source: Lavrinc]. In addition to the nationwide federal regulations, a handful of states have their own standards and restrictions that go above and beyond the national benchmark, which must be met for every car sold within that state. It's really difficult for automakers to develop new technology when these standards are constantly changing. Sometimes, it's nearly impossible for a new innovation to meet the most restrictive demands of a specific market -- even if it passes muster almost anywhere else. Europe, however, is a lot easier for a European carmaker to navigate. In other words, Volvo needed to ensure its tools worked as intended before custom-calibrating them became part of the plan.

If this seems like it's going somewhere else, it is. Volvo's ultimate objective is autonomous driving -- a car that can move with minimal input from the driver. The automaker says studies show that about half of all drivers would be comfortable in a self-driving car and part of the push for autonomous driving technology comes from an increase in potential distractions -- namely, texting [source: Volvo]. Widespread use of this technology could potentially cut down on accidents. Volvo is quick to point out that this shouldn't be a substitute for the driver's judgment -- any input from the driver's controls will override the automatic motions. (That's assuming, of course, that the driver is still awake.)

The progress that's been made in just the last few years eclipses the previous several decades, and at times, it seems like automakers are closer to their goals than they let on. But it's important to note that it's all happening gradually, at a controlled and deliberate pace. It helps everyone -- consumers and government safety regulators -- adjust to the changes slowly, so they don't become overwhelming or dangerous, which would threaten long-term acceptance and future development. If we went from something as simple as cruise control to fully-self-driving cars, without a steady flurry of new tech rollouts in between, people would probably be terrified and unwilling to give it a try. But by the time traffic jam assistance rolls out in 2014, consumers should be pretty well prepared.

Author's Note: How Traffic Jam Assistance Systems Work

When I started researching this assignment, I assumed a feature called "traffic jam assistance" would do something a little different, like help cut down on the occurrence of traffic jams. I'm not really sure how that would work, though, and that was even before I found out I'd be writing about a proprietary Volvo technology. But if it did work -- if a car's various cameras and sensors and trackers could work in harmony to help all traffic flow more smoothly -- well, that would be pretty great. I'm one of the semi-self-righteous types who think that commuters, especially in large urban areas, should make more of an effort to use public transportation. That said, I understand that capacity is not the only factor in a traffic jam. A few sloppy drivers, or a little precipitation, can totally screw up what would otherwise be a smooth traffic flow. Chicago, where I live, is considering implementing pay-to-play congestion-free lanes during peak travel times, and news reports claim a lot of commuters would be willing to cough up the cash to use the special lanes. Seems like this problem would be best solved by a combination of approaches.

I haven't shopped for a new car for years, so I tend to fall behind on new auto safety innovations -- unless I'm writing about them. When I found out that traffic jam assistance wasn't what I assumed, I was a little surprised. Then I found out that Volvo was indeed working on pushing the technology to its limits, and was kind of surprised again. It's interesting that Volvo's SARTRE (Safe Road Trains for the Environment) project is much closer to what I'd think of as "traffic jam assistance," but it's also a lot further away from plausibility. The technology is similar, but the safety concerns increase when multiple vehicles are involved. A malfunction in a road train could back up traffic for miles.

Related Articles


  • Lavrinc, Damon. "Volvo Promises Autonomous Tech by 2014." Wired. Oct. 24, 2012. (Nov. 8, 2012)
  • Marks, Paul. "One Per Cent: Gridlock escape system pioneered by Ford." June 26, 2012. (Nov. 8, 2012)
  • Quick, Darren. "Volvo traffic jam assistance system takes over the chore of stop/start driving." Oct. 23, 2012. (Oct. 30, 2012)
  • Volvo Car Corporation Global Media Newsroom. "Volvo Car Corporation takes the strain out of the daily commute with a technology that automatically follows the vehicle in front." Oct. 23, 2012. (Nov. 1, 2012)
  • Volvo Car Corporation Global Media Newsroom. "Volvo Car Corporation aims for leadership within autonomous driving technology." Sept. 17, 2012. (Nov. 1, 2012)
  • Volvo Car Corporation Global Media Newsroom. "Volvo Car Corporation concludes following the SARTRE project: Platooned traffic can be integrated with other road users on conventional highways." Sept. 17, 2012. (Nov. 1, 2012)

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