Wednesday, September 12, 2012

Will adaptive cruise control spell the end of traffic jams?

Did you know that rear-end collisions account for about 30% of car crashes? For that reason alone, widespread adoption of adaptive cruise control (ACC) can’t come too soon. ACC helps prevent such collisions in two ways: 1) by maintaining a safe, preset distance from the car ahead; and 2) by applying the brakes quickly if that car comes to a sudden stop — more quickly, in fact, than most humans.

Good news is, ACC may soon become pervasive. The folks at Global Industry Analysts crunched some numbers and determined that annual installations of ACC systems will reach 6.9 million units by 2017.

Mind you, ACC isn’t just about safety; it’s also about traffic flow. For instance, a study by Suzuki and Nakatsuji (2003) suggests that travel times shrink significantly when at least 20% of vehicles on the road use ACC. And a study by Kesting et al. (2008) suggests that, in some scenarios, traffic congestion simply disappears when 25% of vehicles use ACC.

Example of adaptive cruise control
Source: Volvo
The picture isn’t all rosy, however. ACC may improve traffic flow, but not in every situation, such as merging from an on-ramp onto a freeway. That said, a study by L. C. Davis (2010) suggests that a technique called cooperative merging can significantly the improve the performance of ACC in this scenario. Meanwhile, a study by Jerath and Brennan (2010) suggests that the benefits associated with ACC may come at a possible cost — “self-organized” traffic jams. This effect, caused mostly by human behavior, may occur in a traffic system where most, but not all, cars use ACC.

Caveats aside, ACC systems continue to evolve. Some drivers tend to slam their brakes and use heavy throttle in traffic, creating congestive shockwaves that ripple down the highway. According to J.C. Power, newer versions of ACC help alleviate this problem by smoothly modulating brakes and throttle in stop-and-go traffic.

And now, a look at ACC from 1939…
If you think the concept of ACC is relatively new, think again. Over 70 years ago, GM created a “Futurama” exhibit for the 1939 World's Fair that showcased a scale-model highway in which cars automatically maintain a safe, efficient distance from one another.

GM predicted this technology would be in place by 1960. They got the timing wrong, but the idea right. Click the video to see a surprisingly prescient look at the car of the future — I’ve already bookmarked the spot for you:

What about you? Have you had much experience with ACC? And if so, has it helped or hindered your driving experience?

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