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January 10, 2011

Eliminate left turns to achieve 20% faster travel times on surface streets

The so-called “superstreet” traffic design results in significantly faster travel times, and leads to a drastic reduction in automobile collisions and injuries, according to North Carolina State University researchers who have conducted the largest-ever study of superstreets and their impacts.

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. 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.

* a 20 percent overall reduction in travel time compared to similar intersections that use conventional traffic designs

* superstreet intersections experience an average of 46 percent fewer reported automobile collisions – and 63 percent fewer collisions that result in personal injury



US motor vehicle deaths by year

2005   43,443   
2006   42,642  
2007   41,059 
2008   37,261  
2009   33,808   

About 90-115 people die every day in vehicle crashes in the United States.

Worldwide an estimated 1.2 million people are killed in road crashes each year and as many as 50 million are injured. Projections indicate that these figures will increase by about 65% over the next 20 years unless there is new commitment to prevention.

There is the potential that widespread superstreet adoption would save several thousand lives per year in the USA and a few hundred thousand lives worldwide.

The paper is called Operational Effects of Signalized Superstreets in North Carolina.

Mythbusters showed that only using right turns saves gas

Here is an online article that analyzes the Mythbuster show on right turns versus left turns

The myth was setup from the perspective of a delivery truck driver. Several locations within the San Francisco area were setup as delivery points, then two routes were derived. The first route was a more “logical” route trying not to favor right turns. This route had eight left turns, four right turns, and a total distance of 5.2 miles. The second route tried to exclude as many left turns as practical. The “right turn” route was 6.8 miles long, had one left turn and twenty-three right turns. Each route visited each stop in the same order.

The MythBusters concluded that right turns were indeed more efficient in their test. While the route favoring right turns was a longer distance and took a longer amount of time, it used only 4.0 gallons of fuel compared to 6.8 gallons of fuel on the “control” route.






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