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Could These Crazy Intersections Make Us Safer?

Read More: http://www.theatlanticcities.com/com...us-safer/4467/

Geometry tells us that the traditional four-way intersection is inherently dangerous. When you plot all of the potential points of conflict on a diagram – and transportation engineers actually do this – it turns out that vehicles have 32 distinct opportunities to collide into one another at the nexus of two two-lane roadways. Cars can crash into each other while merging or diverging from a given lane. Then the worst action happens right in the middle of the interchange, at that perilous point where vehicles turn left across oncoming traffic.

- With that geometry in mind, it becomes clear what we need in the holy grail of intersection design: a scheme that would eliminate left-hand turns while still enabling drivers to move in all four directions. The basic roundabout does this, with only eight relatively less harmful points of conflict. The challenge is to translate that same idea onto much busier roads. You may already be familiar with the “Michigan Left,” also known as the “median U-turn,” which solves this problem by requiring drivers to pass through an intersection, make a u-turn and then re-approach it from the opposite direction, ultimately making a safer right-hand turn. The concept is also intended to improve traffic flow by eliminating that pesky left-turn cycle at the light.

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