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:

As farm jobs decline, food industry work holds steady

Kennesaw State researcher aiming to move AI beyond the cloud

Revolutionizing impedance flow cytometry with adjustable microchannel height

Treating opioid addiction in jails improves treatment engagement, reduces overdose deaths and reincarceration

Can’t sleep? Insomnia associated with accelerated brain aging

Study links teacher turnover to higher rates of student suspensions, disciplinary referrals

How harmful bacteria hijack crops

Crowded conditions muddle frogs’ mating choices

A new way to guide light, undeterred

Researchers uncover how COVID-19 may linger in cancer patients and affect treatment outcomes

Tiny metal figurines from Sardinia's Nuragic civilization in around 1,000 BC reveal extensive ancient Mediterranean metal trading networks

Natural microfibers may degrade differently to synthetic materials under simulated sunlight exposure in freshwater and seawater conditions, with implications for how such pollutants affect aquatic lif

Indian new mums report better postpartum wellbeing when their own mum acts as their primary support - while women whose mother-in-law is the primary caregiver instead report significantly lower overal

Young adult intelligence and education are correlated with socioeconomic status in midlife

Traditional and “existential” wellness vary significantly between US regions

Smartwatches detect early signs of PTSD among those watching coverage of the Oct 7 attacks in Israel

The pandemic may have influenced the trainability of dogs, as reported by their owners

The withdrawal of U.S. funding for tuberculosis could lead to up to 2.2 million additional deaths between 2025 and 2030 inclusive

A ‘universal’ therapy against the seasonal flu? Antibody cocktail targets virus weak spot

Could robots help kids conquer reading anxiety? New study from the Department of Computer Science at UChicago suggests so

UCSB-designed soft robot intubation device could save lives

Burial Site challenges stereotypes of Stone Age women and children

Protein found in the eye and blood significantly associated with cognition scores

USF study reveals how menopause impacts women’s voices – and why it matters

AI salespeople aren’t better than humans… yet

Millions of men could benefit from faster scan to diagnose prostate cancer

Simulations solve centuries-old cosmic mystery – and discover new class of ancient star systems

MIT study explains how a rare gene variant contributes to Alzheimer’s disease

Race, ethnicity, insurance payer, and pediatric cardiac arrest survival

High-intensity exercise and hippocampal integrity in adults with cannabis use disorder

[Press-News.org] Eliminating unexplained traffic jams