{"id":8044,"date":"2016-03-18T06:30:08","date_gmt":"2016-03-18T06:30:08","guid":{"rendered":"http:\/\/revoscience.com\/en\/?p=8044"},"modified":"2016-03-18T06:45:27","modified_gmt":"2016-03-18T06:45:27","slug":"when-slower-is-faster","status":"publish","type":"post","link":"https:\/\/www.revoscience.com\/en\/when-slower-is-faster\/","title":{"rendered":"When slower is faster"},"content":{"rendered":"

Communicating vehicles could ease through intersections more efficiently.<\/strong><\/em><\/span><\/p>\n

\"\u201cAn<\/a>
\u201cAn intersection is a difficult place, because you have two flows competing for the same piece of real estate,\u201d Carlo Ratti says.
Image: Google Earth<\/figcaption><\/figure>\n

CAMBRIDGE, Mass.<\/strong> —\u00a0Imagine a scenario where sensor-laden vehicles pass through intersections by communicating with each other, rather than grinding to a halt at traffic lights. A newly published study co-authored by MIT researchers claims this kind of traffic-light-free transportation design, if it ever arrives, could allow twice as much traffic to use the roads.<\/span><\/p>\n

The study is based on mathematical modeling. The researchers examined a scenario in which high-tech vehicles use sensors to remain at a safe distance from each other as they move through a four-way intersection. By removing the waits caused by traffic lights, these so-called Slot-based Intersections (SIs) speed up traffic flow.<\/span><\/p>\n

\u201cAn intersection is a difficult place, because you have two flows competing for the same piece of real estate,\u201d says Carlo Ratti, a professor of the practice and director of the SENSEable City Lab in MIT\u2019s Department of Urban Studies and Planning, and a co-author of the study. But a system with sophisticated technology and no traffic lights, he adds, \u201cmoves control from the [traffic] flow level to the vehicle level. Doing that, you can create a system that is much more efficient, because then you can make sure the vehicles get to the intersection exactly when they have a slot.\u201d<\/span><\/p>\n

[pullquote]The researchers examined a scenario in which high-tech vehicles use sensors to remain at a safe distance from each other as they move through a four-way intersection.[\/pullquote]<\/p>\n

The greater capacity of the system, notes Paolo Santi, a researcher in the SENSEable City Lab who is a member of the Italian National Research Council and another co-author of the study, does not stem from vehicles moving more quickly. Rather, it comes from creating a more consistent flow at an optimal middle speed, at which automobiles can keep moving.<\/span><\/p>\n

\u201cYou want the car to use the intersection for the shortest possible time,\u201d Santi says.<\/span><\/p>\n

The paper, \u201cRevisiting street intersections using slot-based systems,\u201d appears in the journal\u00a0PLOS One<\/em>. In addition to Ratti and Santi, the paper\u2019s co-authors are Remi Tachet and Stanislav Sobolevsky, also of the SENSEable City Lab; Luis Ignacio Reyes-Castro and Emilio Frazzoli of MIT\u2019s Laboratory for Information and Decision Systems; and Dirk Helbing of the Swiss Federal Institute of Technology in Zurich (ETH Zurich).<\/span><\/p>\n

The \u201cslower is faster\u201d approach<\/strong><\/span><\/p>\n

To see why the system could at least work in theory, consider what the researchers call the \u201cslower is faster\u201d effect. When passengers board an airplane, they tend to move faster if they are in smaller clusters that keep going steadily, as opposed to a scenario in which everyone crowds around the entrance, creating a giant bottleneck.<\/span><\/p>\n

\u201cThe \u2018slower is faster\u2019 effect has been observed in many other contexts related to flow of entities, for instances pedestrians through a narrow space,\u201d Santi explains.<\/span><\/p>\n

As pertains to automotive traffic, Santi continues, \u201cIf you need to slow down the vehicles because there is a lot of traffic, you slow them down early in the road, so they approach the intersection at slow speed, but then when they cross, you use the best speed.\u201d<\/span><\/p>\n

By \u201cearly,\u201d Santi means that control of intelligent vehicles in the proposed system would occur not just at intersections but on the road segments leading to them. The modeling in the paper also finds that the most efficient traffic flow puts vehicles together in batches \u2014 like those smaller groups of passengers boarding a plane \u2014 and then slides them through the intersection accordingly.<\/span><\/p>\n

\u201cIt\u2019s like you use build the phases of a traffic light dynamically,\u201d Santi says.<\/span><\/p>\n

A city of slot cars<\/strong><\/span><\/p>\n

If the key to a light-free, enjoyably efficient traffic intersection is controlling the speeds of cars as they approach intersections, however, it raises further questions. In many cities, intersections with lights are often placed relatively close to each other. So how would the dynamics of traffic at one intersection propagate through a whole urban network of roads?<\/span><\/p>\n

Ratti acknowledges the centrality of this issue and says it is currently the subject of additional study by some of the same researchers.<\/span><\/p>\n

\u201cIf you start from the intersection, this propagates to the city level,\u201d he says. \u201cPart of the work we\u2019re doing is studying that propagation.\u201d<\/span><\/p>\n

Still, despite the complexities that might create, Ratti thinks the intersection-first theoretical approach to urban traffic will prove beneficial: \u201cBecause the intersection is the crucial point, once you solve the intersection, it has a beneficial effect on the whole system.\u201d<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

A newly published study co-authored by MIT researchers claims this kind of traffic-light-free transportation design, if it ever arrives, could allow twice as much traffic to use the roads.<\/p>\n","protected":false},"author":6,"featured_media":8046,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17,28],"tags":[],"class_list":["post-8044","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research","category-techbiz"],"featured_image_urls":{"full":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/03\/MIT-NoLight.jpg",448,299,false],"thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/03\/MIT-NoLight-150x150.jpg",150,150,true],"medium":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/03\/MIT-NoLight-300x200.jpg",300,200,true],"medium_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/03\/MIT-NoLight.jpg",448,299,false],"large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/03\/MIT-NoLight.jpg",448,299,false],"1536x1536":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/03\/MIT-NoLight.jpg",448,299,false],"2048x2048":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/03\/MIT-NoLight.jpg",448,299,false],"ultp_layout_landscape_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/03\/MIT-NoLight.jpg",448,299,false],"ultp_layout_landscape":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/03\/MIT-NoLight.jpg",448,299,false],"ultp_layout_portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/03\/MIT-NoLight.jpg",448,299,false],"ultp_layout_square":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/03\/MIT-NoLight.jpg",448,299,false],"newspaper-x-single-post":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/03\/MIT-NoLight.jpg",448,299,false],"newspaper-x-recent-post-big":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/03\/MIT-NoLight.jpg",448,299,false],"newspaper-x-recent-post-list-image":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/03\/MIT-NoLight.jpg",95,63,false],"web-stories-poster-portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/03\/MIT-NoLight.jpg",448,299,false],"web-stories-publisher-logo":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/03\/MIT-NoLight.jpg",96,64,false],"web-stories-thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2016\/03\/MIT-NoLight.jpg",150,100,false]},"author_info":{"info":["Amrita Tuladhar"]},"category_info":"Research<\/a> Tech<\/a>","tag_info":"Tech","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/8044","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/comments?post=8044"}],"version-history":[{"count":0,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/8044\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media\/8046"}],"wp:attachment":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media?parent=8044"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/categories?post=8044"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/tags?post=8044"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}