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'Superstreet' concept shows promise in real-world test


January 12, 2011

"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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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.


We\'ve had these for a long time in England (on a smaller scale)....next they\'ll invent.....a phone thats mobile!

Mark Penver

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 ...

Stephen Dupree

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.

Kevin Shutt

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).


Apparently the writer\'s never been to Seoul, Korea, where the majority of intersections work this way...

Jeremy Nasmith

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.

Gustavo Rocha

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

Dominic Nolze

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.

Jeff Holden

Got these in Australia too...

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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


@Mark - lol. If I\'m not mistaken, in the US this is referred to as a Michigan left and has been in use since the 60s.


Yeah - those mobile phones being glued to their heads are the reason they have to redesign the roads in the first place.


This has already been implemented in Detroit for many years. Pity that these researchers first didn\'t think to ask, has this been done already? Seems like a waste of effort.

Carl van Bolderen

wouldn\\'t it be nice if this concept were combined with this one: http://www.wimp.com/solarhighways/

Steve Hockenyos

First thing that I thought: \\"where are the separate or wide and safe bicycle lanes?\\" Second: \\"where are the charging station turnouts when the batteries fail?\\" Nice idea, but I doubt that would work in California.

Chris Jordan

This is almost the RULE in Michigan. Whenever there is an intersection that includes at least one divided road, to turn left you have to turn right and then U-turn (or you can pass the intersection, make a u-turn then a right turn). We call it a Michigan Left. Been here for all 3 decades I\'ve been in Michigan.


What a colossal, irritating waste of time for drivers!

The second design is nothing more than a glorified roundabout which favors two of the directions over the other two.

It\'s a twist on the equally irritating method of left turns in New Jersey, where people are apparently incapable of making real left turns.

Unfortunately, this will likely become common because in the end it\'s all about the money, and this would be less expensive than street lights for the same intersection.

Dave Andrews

@Corey, yes, we do have these in Michigan (I\'m in West MI). Lots of them. We call the \"Michigan Turnarounds\".


Lot of misunderstanding here in the comments. While this is similar to roundabouts and Michigan left methods (I live in Michigan, so I am very familiar - they are everywhere, plus we now have several roundabouts), they are not the same. The biggest difference in the US is that this concept can be applied to an existing intersection without tearing down all the buildings on all four corners to make room for a roundabout circle. Difference to a Michigan left is that the cross street traffic can not directly cross the main street. The advantage is that the majority of traffic never has to stop. There is no signal that stops all the main road traffic specifically to allow a car or two (or likely none at all) to cross the more heavily traveled road on the cross street. While a traffic circle does this better in some ways, there are drawbacks that the main road has to slow down, it takes a lot more room (so can not be applied to existing build up areas), and the incoming traffic forces the other traffic inward, where those not experienced with them or not aggressive enough, sit on the inside for a revolution or two to get out. I\'m aggressive enough (wife says too much so) but I\'ve seen people get stuck and heard others tell me they have been. This system will allow all levels of drivers to navigate it more simply. This is not more complex than a traffic circle, especially for those that grew up driving US style road systems.

Mark in MI

If I am faced with a raging fast street filled with maniacs in both lanes (which unfortunately is at the end of my street during rush hour) and I know I\'ll have to wait for 10 minutes before I\'ll ever get a chance to turn left (and I have a 5 liter V8!) I will very frequently make a right turn, then a U-turn. It makes perfect sense to me to make this the primary functionality of the road. In my area, I have seen a few newer intersections that are about 2/3 of this idea, if there were a couple more on either side of that intersection it would be a superstreet.


Umm, How does it work for trucks? I would not like to be in the wherabouts when one of the longer ones are making a uturn on a 2 or 4 lane street. Even on the quite wide street in the picture they have to broaden the road. Roundabouts work well though and they actually don´t have to be that large.

Conny Söre

Americans are many things. Inventive is not one of them. With a slight change in geometry, this system has been around in the UK and Europe for more than fifty years and in Australia for close to twenty years. They are called ROUND-A-BOUTS.


Definitely see the main advantage is retrofitting existing 90 degree intersections for near-roundabout efficiency.

Love roundabouts, but indeed, there is a small amount of slowing involved, which is not necessary for this type of proposed intersection.

As an engineer, one has to have many intersection \"tools\" in your toolbag, and implement each one appropriately for each individual location. Mo\' tools is betta\' !


Matt Rings

I am noticing here in Australia that roundabouts are being replaced with traffic lights when the traffic volume gets above a certain amount, especially with two major roads. The problems with roundabouts is that even straightahead traffic has to slow down and if you are trying cross a major road you may take ages to get a break. With traffic lights the wait time for the side street can be significantly reduced. Trucks are a problem, but they already have problems on roundabouts, so I am sure something can be figured out.


I\'ve seen something similar in Calgary. I\'ve traveled in France a couple of times and I find that roundabouts (rond-point) are the best thing there is.


Bayani Fernando, introduced the U-turn concept in Metro Manila when he was Chairman of the Metropolitan Manila Development Authority (MMDA) from 2002 to 2009. He has also constructed a Urban Interchange with two elevated u-turns which a full inverted clover leaf interchange. Contact MMDA traffic head at neomie_recio@yahoo.com for details.

Martin Ongpin

An interesting idea but I can\'t see it working here, in Turkey, where some drive the wrong way up dual-lane streets in cities(and on dual-carriageways!) to avoid having to travel further and make a U-turn.

Also good if you\'ve forgotten something and need to go back home (office) to collect it!

How is the length of the U-turn section decided? road speed? projected traffic flow? etc.


The roundabout is a much slicker, more environmentally friendly, and safer way. You don\'t have to waste fuel and go up a road you don\'t want to go on. Drivers have adjusted their speed and awareness for the roundabout, whereas for a \"U\" turn drivers are still speeding. It is therefore safer. I think roundabouts are superior to traffic lights, all give way junctions, and a general free for all. You give way to the traffic on the roundabout, that is the main rule and the traffic flows freely.



Michigan has been using this kind of intersection for about 10 years. They even earned the nickname \"Michigan U Turn\" because of it. The city of Holland Michigan started adapting them first if I remember correctly. The advantage they have over stoplights or even roundabouts is that its safer than either and faster than roundabouts. I like roundabouts, but they have their limits. Specifically, they are inefficient when more than two lanes of busy traffic are introduced. They are faster because traffic doesn\'t have to slow down; only the left-turning traffic slows down. I find them very effective in hi-traffic areas, but I still like roundabouts over rural 4-way stops.

Eric Nyhof

Hello everyone, I want to try and clear up some misconceptions and possibly add some info about this design. To help illustrate my point you can view a diagram of this design here: http://attap.umd.edu/UAID.php?UAIDType=3&Submit=Submit&iFeature=1 That should also answer how pedestrians and bicycles would traverse the intersection.

Firstly, a great benefit to this design that wasn\'t discussed is that each major street direction can be signalized independently of one another. In a situation where there are several of these signals one after another (in a corridor), a driver can drive the speed limit (the speed the signals would most likely be timed at) and traverse through the corridor without having to stop. This is called progression and is the holy grail of signal timers everywhere. This is also a method for controlling speeders as going too fast will put you at the next signal too soon and be forced to stop at a red light.

Secondly, right turners never fear! In a signalized situation you could actuate the signal so the signal system would know to stop through movements on the major street if you sit at the light too long. Then the light for the u-turn should be timed to allow you to move through and on your way without too much delay. In an unsignalized situation there probably wasn\'t enough traffic to warrant a signal; so you should be fine. If you\'re not, lobby some one for $200-350K to signalized the thing.

For the round-a-bouters here...This design is meant for corridor environments where there is a disproportionate number of vehicles on the major arterial vs. the minor street. Round-a-bouts work best as a single lane loop at the intersection of two minor streets (two lane streets). Adding another lane to a round-a-bout does not double the capacity but only about half of the original capacity. So you can see there\'s a limit there.

For the Michigan u-turn die hards...The main difference in this design and the Michigan u-turns is that there are left turn bays at the minor streets. A driver isn\'t generally allowed the make any lefts at a true MI u-turn intersection. I will concede that the designs are quite similar but they are meant for different situations.

@Conney The radii of the turn movements should be suitable for trucks as long as they are designed in accordance with the AASHTO \'Green Book.\' It\'s the bible for traffic engineers and shows the limits of turning radii for all standard vehicles. Also, in the picture you can see a bulge out exactly for trucks across from the u-turn lane.

@agulesin The length of the U-turn section is determined by road speed and timing considerations (in a perfect world). I believe the ideal length from the minor street is 300-500 feet. If one were to try and plop this sucker into an existing roadway it may be limited by the spacing to the next intersection.

Cheers! and Go Pack! (NCSU)


I visited Manila Philippines over 2 years ago and I drove over this a few times in a multilane road and bumper to bumper traffic. The traffic negotiation felt faster and safer. I felt safer over this that crossing their traffic lights and Traffic lights and roundabouts in Australia. I think it works because there is minimal speed difference between all the vehicle in the traffic control system.

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Has merit if it makes up for the \"average\" (most) drivers--who don\'t have enough intelligence to operate can openers, far less drive a ton at 60 mph.

Better to ticket, ticket, ticket until the worst are in jail, can\'t afford to drive or somehow mature enough to drive. Yeah, like the last one is ever going to happen.

If the governments keep bailing out losers like gm and ford (that didn\'t have the honor to die--yeah, more cars, that will help, geniuses), governments certainly are never going to do what they need to do to address the real issue: get the idiots off the road that never should have been there.

Fred Meyers

I don\'t get it at all. In the clicked on pic above there are two trucks making left turns. The large trailer truck is obviously not going to make a u turn and the smaller truck is in a lane marked for left turns. This is in complete contradiction to the description--or am I missing something?!? If I\'m not missing anything then what a bunch of BS the concept and article are!

Al Mayberry
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