Revisiting the origin of the "Michigan Left"

As part of our M I Curious project , Nick Ochal asked Michigan Radio this question: What is the origin of the infamous "Michigan Left" that befuddles so many out-of-staters? Last month, Stateside's Cynthia Canty put the question to Joseph Hummer , a professor with the College of Engineering at Wayne State University. According to Hummer, Michigan Lefts emerged as a way to decrease traffic congestion on roads that were designed for street cars. After this interview aired, a listener wrote in questioning the link between street cars and Michigan Lefts. They wrote: "... the connection between the Michigan Left and the street car lines was tangential at best and most definitely not the cause-and-effect relationship the Wayne State University professor made it out to be." So, what is the true history of this infrastructural oddity? For all those who may not be so acquainted, a Michigan Left is an intersection at which left turns are not allowed. Instead, to turn left, drivers must drive