PRESS-NEWS.org - Press Release Distribution
PRESS RELEASES DISTRIBUTION

Eliminating unexplained traffic jams

2013-10-29
(Press-News.org) Contact information: Sarah McDonnell
s_mcd@mit.edu
617-253-8923
Massachusetts Institute of Technology
Eliminating unexplained traffic jams CAMBRIDGE, MA -- Everybody's experienced it: a miserable backup on the freeway, which you think must be caused by an accident or construction, but which at some point thins out for no apparent reason.

Such "traffic flow instabilities" have been a subject of scientific study since the 1930s, but although there are a half-dozen different ways to mathematically model them, little has been done to prevent them.

At this month's IEEE Conference on Intelligent Transport Systems, Berthold Horn, a professor in MIT's Department of Electrical Engineering and Computer Science, presented a new algorithm for alleviating traffic flow instabilities, which he believes could be implemented by a variation of the adaptive cruise-control systems that are an option on many of today's high-end cars.

A car with adaptive cruise control uses sensors, such as radar or laser rangefinders, to monitor the speed and distance of the car in front of it. That way, the driver doesn't have to turn the cruise control off when traffic gets backed up: The car will automatically slow when it needs to and return to its programmed speed when possible.

Counterintuitively, a car equipped with Horn's system would also use sensor information about the distance and velocity of the car behind it. A car that stays roughly halfway between those in front of it and behind it won't have to slow down as precipitously if the car in front of it brakes; but it will also be less likely to pass on any unavoidable disruptions to the car behind it. Since the system looks in both directions at once, Horn describes it as "bilateral control."

Traffic flow instabilities arise, Horn explains, because variations in velocity are magnified as they pass through a lane of traffic. "Suppose that you introduce a perturbation by just braking really hard for a moment, then that will propagate upstream and increase in amplitude as it goes away from you," Horn says. "It's kind of a chaotic system. It has positive feedback, and some little perturbation can get it going."

Doing the math

Horn hit upon the notion of bilateral control after suffering through his own share of inexplicable backups on Massachusetts' Interstate 93. Since he's a computer scientist, he built a computer simulation to test it out.

The simulation seemed to bear out his intuition, but to publish, he needed mathematical proof. After a few false starts, he found that bilateral control could be modeled using something called the damped-wave equation, which describes how oscillations, such as waves propagating through a heavy fluid, die out over distance. Once he had a mathematical description of his dynamic system, he used techniques standard in control theory — in particular, the Lyapunov function — to demonstrate that his algorithm could stabilize it.

Horn's proof accounts for several variables that govern real-life traffic flow, among them drivers' reaction times, their desired speed, and their eagerness to reach that speed — how rapidly they accelerate when they see gaps opening in front of them. Horn found that the literature on traffic flow instabilities had proposed a range of values for all those variables, and within those ranges, his algorithm works very efficiently. But in fact, for any plausible set of values, the algorithm still works: All that varies is how rapidly it can smooth out disruptions.

Horn's algorithm works, however, only if a large percentage of cars are using it. And laser rangefinders and radar systems are relatively costly pieces of hardware, which is one of the reasons that adaptive cruise control has remained a high-end option.

Digital cameras, on the other hand, have become extremely cheap, and many cars already use them to monitor drivers' blind spots. "There are several techniques," Horn says. "One is using binocular stereo, where you have two cameras, and that allows you to get distance as well as relative velocity. The disadvantage of that is, well, two cameras, plus alignment. If they ever get out of alignment, you have to recalibrate them."

Time to impact

Horn's chief area of research is computer vision, and his group previously published work on extracting information about distance and velocity from a single camera. "We've developed monocular methods that allow you to very accurately get the ratio of distance to velocity," Horn says — a ratio known in transportation studies as "time to contact," since it captures information about the imminence of collision. "Strangely, while it's, from a monocular camera, difficult to get distance accurately without additional information, and it's difficult to get velocity accurately without additional information, the ratio can be had." In ongoing work, Horn is investigating whether his algorithm can be adapted so that it uses only information about time to contact, rather than absolute information about speed and distance.

###

END



ELSE PRESS RELEASES FROM THIS DATE:

Sun continues to emit solar flares

2013-10-29
Sun continues to emit solar flares After emitting its first significant solar flares since June 2013 earlier in the week, the sun continued to produce mid-level and significant solar flares on Oct. 27 and Oct. 28, 2013. Solar flares are powerful ...

Study challenges soil testing for potassium and the fertilizer value of potassium chloride

2013-10-29
Study challenges soil testing for potassium and the fertilizer value of potassium chloride URBANA, Ill. – In the chemical age of agriculture that began in the 1960s, potassium chloride (KCl), ...

Researchers turn to technology to discover a novel way of mapping landscapes

2013-10-29
Researchers turn to technology to discover a novel way of mapping landscapes University of Cincinnati researchers are blending technology with tradition, as they discover new and improved methods for mapping landscapes. The research is newly published in the Journal ...

OU research team finds a common bioindicator resistant to insecticides

2013-10-29
OU research team finds a common bioindicator resistant to insecticides In a novel study, a University of Oklahoma researcher and collaborators found a common bioindicator, Hyalella azteca, used to test the toxicity of water or sediment was resistant to insecticides used ...

An eye-opener: NASA sees Hurricane Raymond reborn for a brief time

2013-10-29
An eye-opener: NASA sees Hurricane Raymond reborn for a brief time Tropical Storm Raymond moved away from western Mexico and into warmer waters with less wind shear over the weekend of Oct. 26-27, where it strengthened into a hurricane again. NASA's Aqua satellite ...

NASA catches glimpse of the brief life of Southern Indian Ocean's first tropical cyclone

2013-10-29
NASA catches glimpse of the brief life of Southern Indian Ocean's first tropical cyclone The first tropical cyclone of the Southern Indian Ocean season lasted about one day. Tropical Cyclone 01S was born on Oct. 27 and by Oct. 28 had become a remnant low. The ...

Neutrons, electrons and theory reveal secrets of natural gas reserves

2013-10-29
Neutrons, electrons and theory reveal secrets of natural gas reserves Gas and oil deposits in shale have no place to hide from an Oak Ridge National Laboratory technique that provides an inside look at pores and reveals structural information potentially vital ...

The people's choice: Americans would pay to help monarch butterflies

2013-10-29
The people's choice: Americans would pay to help monarch butterflies Americans place high value on butterfly royalty. A recent study suggests they are willing to support monarch butterfly conservation at high levels, up to about 6 ½ billion dollars if extrapolated ...

UCSB researcher documents the enduring contaminant legacy of the California gold rush

2013-10-29
UCSB researcher documents the enduring contaminant legacy of the California gold rush (Santa Barbara, Calif.) –– An unintended legacy of California's gold rush, which began in 1848, endures today in the form of mercury-laden sediment. New research ...

Moderate exercise not only treats, but prevents depression

2013-10-29
Moderate exercise not only treats, but prevents depression TORONTO, ON – Physical activity is being increasingly recognized as an effective tool to treat depression. PhD candidate George Mammen's review published in the October issue of the American ...

LAST 30 PRESS RELEASES:

Thirty-year mystery of dissonance in the “ringing” of black holes explained

Less intensive works best for agricultural soil

Arctic rivers project receives “national champion” designation from frontiers foundation

Computational biology paves the way for new ALS tests

Study offers new hope for babies born with opioid withdrawal syndrome

UT, Volkswagen Group of America celebrate research partnership

New Medicare program could dramatically improve affordability for cancer drugs – if patients enroll

Are ‘zombie’ skin cells harmful or helpful? The answer may be in their shapes

University of Cincinnati Cancer Center presents research at AACR 2025

Head and neck, breast, lung and survivorship studies headline Dana-Farber research at AACR Annual Meeting 2025

AACR: Researchers share promising results from MD Anderson clinical trials

New research explains why our waistlines expand in middle age

Advancements in muon detection: Taishan Antineutrino Observatory's innovative top veto tracker

Chips off the old block

Microvascular decompression combined with nerve combing for atypical trigeminal neuralgia

Cutting the complexity from digital carpentry

Lung immune cell type “quietly” controls inflammation in COVID-19

Fiscal impact of expanded Medicare coverage for GLP-1 receptor agonists to treat obesity

State and sociodemographic trends in US cigarette smoking with future projections

Young adults drive historic decline in smoking

NFCR congratulates Dr. Robert C. Bast, Jr. on receiving the AACR-Daniel D. Von Hoff Award for Outstanding Contributions to Education and Training in Cancer Research

Chimpanzee stem cells offer new insights into early embryonic development

This injected protein-like polymer helps tissues heal after a heart attack

FlexTech inaugural issue launches, pioneering interdisciplinary innovation in flexible technology

In Down syndrome mice, 40Hz light and sound improve cognition, neurogenesis, connectivity

Methyl eugenol: potential to inhibit oxidative stress, address related diseases, and its toxicological effects

A vascularized multilayer chip reveals shear stress-induced angiogenesis in diverse fluid conditions

AI helps unravel a cause of Alzheimer's disease and identify a therapeutic candidate

Coalition of Autism Scientists critiques US Department of Health and Human Services Autism Research Initiative

Structure dictates effectiveness, safety in nanomedicine

[Press-News.org] Eliminating unexplained traffic jams