Finally we figured it out! We even learned that it has a name. Here's an example of what a Michigan Left Turn is like:
Often maligned, often misunderstood, the Michigan Left Turn is an operation which causes much consternation among out-of-state drivers and nary a second thought from locals. Developed in Michigan in 1960...these turning set-ups exist across the entire state, from Niles to Escanaba and from Detroit to Marquette. (Yes, the Upper Peninsula has Michigan Lefts!)
The Michigan Left was developed to avoid the interlocking left-turn movements along divided highways. In this way, the only turning movements allowed at such an intersection are right-hand turns. Traffic lights can be placed at busier Michigan Left intersections if warranted. For the most heavily-used "crossovers," specialized traffic signals may be placed to ensure traffic does not back up on the highway waiting to turn left.
Quote taken from http://www.michiganhighways.org/indepth/michigan_left.html