If integrated into adaptive cruise-control systems, a new algorithm could mitigate the type of freeway backup that seems to occur for no reason.
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.
Go deeper with Bing News on:
- Traffic lights work a little differently on the Gold Coast. How do they compare?on February 4, 2020 at 12:27 pm
"STREAMS is also used for other traffic coordination, including motorway management, via variable-speed-limit and variable-message signs, ramp-signal management and incident management," the ...
- DIY Virtual Traffic Jam With A Bucket Of Old Phoneson February 4, 2020 at 10:31 am
You could theoretically use this to manipulate traffic flow in your location, not that you actually should but it is definitely possible to do. A few people with phone carts could in theory shut down ...
- CRRI begins survey to improve traffic flow on arterial Noida roadson February 4, 2020 at 7:32 am
has begun a survey of Noida roads in order to suggest structural changes that can improve traffic flow on major roads in Noida. The traffic police and Noida authority has engaged CRRI to conduct ...
- Google responds after user hacks Google Maps traffic flow with 99 smartphoneson February 4, 2020 at 3:09 am
Google says it appreciates creative uses of Google Maps after a user ‘hacked’ traffic flow data in an area using 99 second hand phones.
- Supreme Court plea seeks clearance of protesters in Delhi’s Kalindi Kunj- Shaheen Bagh stretch to restore smooth traffic flowon February 3, 2020 at 8:24 pm
NEW DELHI: To seek an end to the blockade and restore smooth traffic flow on Delhi’s Kalindi Kunj- Shaheen Bagh stretch, a petition was filed in the SC on Monday seeking direction for Centre on ...
Go deeper with Google Headlines on:
Go deeper with Bing News on:
Traffic flow instabilities
- Introducing The Raspberry Pi 3on January 30, 2020 at 4:00 pm
TL;DR: The Raspberry Pi 3 Model B is out now. This latest model includes 802.11n WiFi, Bluetooth 4.0, and a quad-core 64-bit ARM Cortex A53 running at 1.2 GHz. It’s a usable desktop computer.
- Global elite descends upon Davos as World Economic Forum kicks offon January 20, 2020 at 10:17 am
Chief executives around the world are eyeing up Britain as a key target for growth, viewing the UK as an increasingly stable place to do business in a world beset by political and economic ...
- CONTAINERISED TRUCKS: Tanker drivers dying in silence in Apapa — Comrade Atandaon January 11, 2020 at 10:54 pm
They are on the road 24 hours thereby obstructing free flow of traffic to and fro the depot ... financial and family instabilities. Many of our members have been attacked by touts, especially ...
- Quantitative earthquake-like statistical properties of the flow of soft materials below yield stresson January 6, 2020 at 4:00 pm
The flow behavior of soft materials below the yield stress can be rich and is not fully understood. Here, we report shear-stress-induced reorganization of three-dimensional solid-like soft ...
- Bell-Boeing JV Wins Deal to Support V-22 Flight Test Analysison January 1, 2020 at 4:00 pm
Considering such a bountiful spending provision, defense majors like Boeing and Textron are witnessing increased flow of contracts ... geopolitical instabilities and increased defense spending.