Anyone who has ever made a left turn in a busy intersection understands that it can be a stressful maneuver. Not only do you have to wait impatiently for a break in the stream of cars coming the opposite direction, but you often hold up a line of traffic and even risk getting into a collision if other drivers aren't following the rules of the road.
But despite how standard it may seem to turn left into traffic, that's actually not an inevitable part of driving. There is an intersection design that could save you all that trouble.
The "diverging diamond interchange" creates designated ramps that gradually direct cars to veer left or right, without ever requiring them to cross in front of ongoing traffic.
Though it might look complicated, it's actually a simple concept. Say, for example, that you're driving from west to east. As you come to the intersection, a red light may stop you as you let cars going the other way pass. (This is the only time streams of traffic cross each other.) If you want to turn right, a lane peels off and merges with the road carrying southbound cars. If you want to turn left, you just follow the ramp that veers to the north.
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Watch it in action:
Since 2009, this diamond design has been implemented in 62 intersections across 22 US states, according to Wired.
And it's working: In a recent study comparing crash data from before and after a series of intersections were converted to the new design, researchers found that overall crashes were reduced by 33%, while crashes that result in injury were reduced by 41%.
The diverging diamond was popularized in the US by Gilbert Chlewicki, the founder of Advanced Transportation Solutions, a transportation planning and design firm. Chlewicki wrote a term paper about the concept as a graduate student in 2000, and he has devoted much of his life's work to promoting the design ever since. He has published several papers about it and has presented at conferences throughout the US and Canada.
The first diamond interchange in the US was built in Springfield, Missouri, in 2009 (France has had a few since the 1970s), and Chlewicki attended the ribbon cutting. In a survey conducted there later, 95% of drivers surveyed said there had been less traffic congestion since the new intersection opened, and 97% said they felt safer.
According to a map on Chlewicki's official website for the design, many more such intersections are being planned and constructed, mostly in Midwestern states. The rest of the country's commuters will have to continue suffering through regular left turns until the trend catches on elsewhere.
