Traffic congestion? Add more road! Ten miles of it. And make it a spiral.
In their book "Tooling," New York-based architects Benjamin Aranda and Chris Lasch suggested a 10-mile spiral of roadway that will act as a traffic decongestion device by adding more road!
First, it acts as a massive traffic decongestion device... by adding significant mileage to the highway in the form of a spiral. The second purpose is less infrastructural and more cultural: along the spiral you can play slots, roulette, get married, see a show, have your car washed, and ride through a tunnel of love, all without ever leaving your car. It is a compact Vegas, enjoyed at 55 miles per hour and topped off by a towering observation ramp offering views of the entire valley floor below.
Link - via Exploding Aadrvark