Save Time And Lives: Take It To The Superstreets!

01.10.2011 |

Super indeed. These traffic patterns can cut travel time by 20 percent, and injuries from traffic accidents by over 60 percent.

Everyone hates traffic. Everyone also hates car accidents. What if there was a traffic pattern that could cut travel times at busy intersections by 20 percent, and cut collision-related injures by over 60 percent? Good news – there is! The pattern is called, fittingly enough, a superstreet.

The superstreet concept has been around for 20 years, but no one had gotten around to doing a large-scale study of how these superstreets function in the real world until recently. A new study from NC State researchers is the largest-ever examination of superstreet impacts, and found that the traffic design makes a huge difference. For example, superstreet intersections have 63 percent fewer collisions that result in personal injury than comparable intersections using traditional traffic design. (Superstreets had 46 percent fewer collisions overall). Drivers also negotiated superstreet intersections 20 percent faster than traditional intersections. That’s pretty impressive.

Here’s how superstreets work: a superstreet is a surface street (not a highway) where the left-hand turns from side streets are re-routed, as is traffic from side streets that needs to cross the thoroughfare (see the diagram at the top of this post). In both instances, drivers are first required to make a right turn and then make a U-turn around a broad median. 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.

Most superstreets look like the one on the left in the above diagram, where drivers on the superstreet itself can turn left onto a side street. However, some don’t allow left-hand turns, like the one on the right in the above diagram. Either way, they’re faster and safer.

With benefits like those shown in this study, we can likely expect to see more traffic engineers adopting the superstreets model. Taking it to the superstreets (if you will).



12 Responses to “Save Time And Lives: Take It To The Superstreets!”

  1. [...] road; if they wish to go left, they’ll first have to go right and then make a U-turn. And superstreets, or restricted crossing U-turns, which are found in some other parts of the country, such as North [...]

  2. Patrick Pentz says:

    Another approach that is becoming more prevelent in Washington state (Seattle, anyway) is round-a-bouts. Has any study been performed on these?

    In New Jersey there are intersections similar to ‘superstreets’ called ‘jug-handles’… are they actually the same; if not, any additional info on these?

  3. Matt Shipman says:

    Do jug handles utilize ramps? If so, they’re somewhat different. Also, I think jug handles focus on not allowing people on the main artery to turn left. Superstreets focus more on not allowing traffic on the cross streets to turn left. I’m sure there have been studies on roundabouts, but I’m not familiar with them. Apparently, Kansas State has a center that focuses on studying roundabouts. You may want to check out their site: http://www.k-state.edu/roundabouts/

  4. Kate says:

    where in this arrangement could you put a pedestrian crossing?

  5. Matt Shipman says:

    Great question. My understanding is that pedestrian crossings are at a diagonal. Studies have shown that pedestrian crossings at superstreets are also safer than on comparable streets with traditional traffic patterns. Again, likely due to the absence of left-hand turns from the side streets onto the main thoroughfare.

  6. Will says:

    They use this design extensively in Michigan, it is not pedestrian or cyclist friendly at all. The main benefit is that it allows cars to go fast on the main street. This “benefit” is also a hazard unto itself in many applications, and this should not be used in any sort of urban context, or even in suburban. Perhaps for rural roads and state highways it makes sense, but for little else. As a previous comment points to, roundabouts are preferable for areas where slower speeds are necessary.

  7. Matt Shipman says:

    You’re referring to so-called “Michigan intersections.” Apparently they are different from superstreets, though I don’t understand the specifics.

  8. [...] This superstreet idea, I think I like. While I hate U-Turns, that’s only because my GPS will demand them on streets that are not designed for them. Here, no problem. [...]

  9. Paul says:

    Matt, I see a significant problem with this concept in Florida or any high traffic area. Most of the major streets in this area are four lanes (two lanes each way). At most times of the day the traffic is so heavy that a RIGHT turn from a side street onto the main street is impossible until the traffic light turns. The super street plan would only work on a main street with traffic sparse enough to not only enable a driver to find an opening to make a right turn but to enable the driver to quickly merge left for the U-turn. Acceleration to traffic speeds and a left lane merge in Florida would be impossible in less than a mile. The jug handle traffic light turns used in New Jersey are the only way to reduce signals while eliminating left turns in high traffic areas.

  10. Joe Hummer says:

    I am the Principal Investigator of the study on which the press release was based. Thanks for all of the comments. I have a few brief responses to a couple. On roundabouts, there has been much research in the past 20 years. That research has shown that roundabouts are more efficient and safer than conventional intersections in their niche. However, their niche is smaller intersections on lower-volume and lower-speed streets, not the big intersections that a superstreet is intended for. Matt is correct that jughandles are different from superstreets, since jughandles use a ramp from the main street to the side street. Our research shows that superstreets are generally better than jughandles and require less space. Matt is right that a superstreet is different from a Michigan left (median u-turn). Being from Michigan I know this well. A Michigan left reroutes all four left turns while allowing the side street throughs; a superstreet reroutes the sidestreet lefts and throughs while allowing the main street lefts. That little difference makes a big difference in operation. A Michigan left is better at huge intersections between two arterials, while a superstreet better serves an intersection between an arterial and a medium-sized side street. Finally, the question on peds and bikes at a superstreet is a good one. So far no one has installed a superstreet in a ped and bike area, so we are just theorizing. The theory is that a superstreet offers peds a slow but safe diagonal crossing; that vehicle speeds on a superstreet could be kept low (due to flexible signal timing) benefiting peds; and that we could install ped crossing signals anywhere on a superstreet with little extra vehicle delay. Bikes making a side street left and through do not fare well in current superstreet designs, but all other bikes should be fine, and we are working on ways to help those affected bikes. Again, thanks for the terrific comments, hope this helps your understanding.

  11. [...] divided road; if they wish to go left, they’ll first have to go right and then make a U-turn. And superstreets, or restricted crossing U-turns, which are found in some other parts of the country, such as North [...]

  12. [...] divided road; if they wish to go left, they’ll first have to go right and then make a U-turn. And superstreets, or restricted crossing U-turns, which are found in some other parts of the country, such as North [...]

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