Urban Transport

'Superstreet' concept shows promise in real-world test

'Superstreet' concept shows pr...
"Superstreet" traffic designs result in faster travel times and significantly fewer accidents, according to the new study. Credit: Dr. Joe Hummer, North Carolina State University
"Superstreet" traffic designs result in faster travel times and significantly fewer accidents, according to the new study. Credit: Dr. Joe Hummer, North Carolina State University
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"Superstreet" traffic designs result in faster travel times and significantly fewer accidents, according to the new study. Credit: Dr. Joe Hummer, North Carolina State University
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"Superstreet" traffic designs result in faster travel times and significantly fewer accidents, according to the new study. Credit: Dr. Joe Hummer, North Carolina State University
Superstreets are thoroughfares where the left-hand turns from side streets are re-routed, as is traffic from side streets that needs to cross the thoroughfare. In both instances, drivers are first required to make a right turn and then make a U-turn around a broad median. This diagram shows superstreet traffic patterns. The lefthand image is of the most common superstreet design, in which traffic on the superstreet itself can turn left. In the righthand image, traffic on the superstreet cannot turn left. Credit: Dr. Joe Hummer, North Carolina State University
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Superstreets are thoroughfares where the left-hand turns from side streets are re-routed, as is traffic from side streets that needs to cross the thoroughfare. In both instances, drivers are first required to make a right turn and then make a U-turn around a broad median. This diagram shows superstreet traffic patterns. The lefthand image is of the most common superstreet design, in which traffic on the superstreet itself can turn left. In the righthand image, traffic on the superstreet cannot turn left. Credit: Dr. Joe Hummer, North Carolina State University

No left turn. That is the simple concept behind the Superstreet traffic design which promises significantly faster travel times, plus a drastic reduction in auto-collisions and injuries. These superstreets are ground level streets – not raised freeways or highways – that allow for greater volume of thru-traffic by re-routing traffic from side streets that would normally be trying to get across the main road. While the idea has been around in urban transport modeling textbooks for over 20 years, researchers from the North Carolina State University have been the first to test the concept in the real world and the results are promising.

The central concept to the superstreet design is a thoroughfare, a stream of constantly moving traffic that follows a main arterial road. Drivers wanting to cross the thoroughfare or to turn left are first required to make a right turn, joining the main stream of traffic. A little way down the superstreet they then make a U-turn after which they can continue on along the thoroughfare if they had been trying to turn left or they can turn right into the side street if this was their planned route. While this may seem time-consuming, the study shows that it actually results in a significant time savings since drivers are not stuck waiting to make left-hand turns or for traffic from cross-streets to go across the thoroughfare.

"The study shows a 20 percent overall reduction in travel time compared to similar intersections that use conventional traffic designs," Dr Joe Hummer, professor of civil, construction and environmental engineering at NC State and one of the researchers who conducted the study said. "We also found that superstreet intersections experience an average of 46 percent fewer reported automobile collisions – and 63 percent fewer collisions that result in personal injury."

The researchers assessed travel time at superstreet intersections as the amount of time it takes a vehicle to pass through an intersection from the moment it reaches the intersection – whether traveling left, right or straight ahead. The travel-time data were collected from three superstreets located in eastern and central North Carolina, all of which have traffic signals. The superstreet collision data were collected from 13 superstreets located across North Carolina, none of which have traffic signals.

A Paper on the travel time research will be presented on January 24 at the Transportation Research Board Annual Meeting in Washington D.C. The Paper is co-authored by Hummer, former NC State graduate students Rebecca Haley and Sarah Ott, and three researchers from NC State's Institute for Transportation Research and Education: Robert Foyle, associate director; Christopher Cunningham, senior research associate; and Bastian Schroeder, research associate. The collision research was part of an overarching report of the study submitted to the North Carolina Department of Transportation (NCDOT) last month, and is the subject of a forthcoming paper. The study was funded by NCDOT.

33 comments
Mark Penver
We\'ve had these for a long time in England (on a smaller scale)....next they\'ll invent.....a phone thats mobile!
Stephen Dupree
I\'m guessing that the study did not include bicycles as a viable means of transportation. It would only take a very few of these intersections on a given route to significantly increase the distance and/or time for a bike commuter. Of course, if it means they get there alive ...
Kevin Shutt
This concept is used to a certain extent down here in Highlands County Florida, though not at major intersections. But, most secondary side-streets are right turn only, reducing the amount of lanes a driver must concern themselves with. A right turn, then a u-turn is supposed to be much safer and easier. Though initially annoyed and skeptical, I am warming to this concept.
Adrien
still need to wait for a clear run to turn right. this is just a stretched round-about (something found all over the place in New Zealand).
Jeremy Nasmith
Apparently the writer\'s never been to Seoul, Korea, where the majority of intersections work this way...
Gustavo Rocha
Well, isn\'t that what roundabouts are for? Roundabouts are compact versions of the elaborate setup described in this article: if you want to cross the main street on a roundabout you enter the roundabout with a right turn, follow the roundabout until the intended exit (therefore effectively making an U-turn) and then exit the roundabout with a right turn. No left-turns, no perpendicular crossings. This is at most a roundabout which is longer along the main street than it is along the secondary streets that cross it. And, it needs more traffic signs to be correctly understood (lane selection signs, U-turn signs...). Even worse, the driver that tries to cross the main street has to cross all the lanes on either side of the main street in order to get into the U-turn allowed lanes and to get into the second right turn allowed lanes, which he doesn\'t need to when on a roundabout (on a roundabout the driver can/should stay on the right-side/outermost lane until his exit). All in all roundabouts are better.
Dominic Nolze
i think, a big circle is a very nice system... fast and you can leave in alot of directions. make the cars more slow before with some fence or bumper, and its a quite elegant solution.... correct me if i am wrong with what i am saying
Jeff Holden
Britain has overcome this problem already by the simple expedient of using roundabouts with a clear rule about who must give way to whom when entering a roundabout. The traffic there flows faster, with a much lower accident rate and avoids unnecessary travel in the \'wrong\' direction simply to join the appropriate traffic stream. It\'s U-turns that are dangerous - especially when a huge truck blocks three lanes innorder to make its turn. Sorry guys, this one won\'t fly.
Facebook User
Got these in Australia too...
dsloan48
in New Jersey they\'re called circles ( a little smaller ) The problem still remains that you have to cut across multiple lanes of traffic in order to use them. At 60 - 65 mph it\'s still VERY TREACHEROUS. Whatever happened to that 50\'s idea that we would all have a family gyroplane to replace the car by the year 2000? LOL