Interstate highways have played a crucial role in the development of Michigan and the country as a whole. With 2006 marking the 50th anniversary of the Interstate System, here are some noteworthy facts with regards to Michigan's Interstate highways.

The world's first freeway-to-freeway interchange was opened at Interstate 94 (Edsel Ford) and M-10 (John Lodge) in Detroit on January 18, 1955, permitting motorists to make turns "simply by moving in the direction they wish to go."

The longest highway in Michigan is Interstate 75 which runs 395 miles from the Ohio border to the International Bridge in Sault Ste. Marie.

The Mackinac Bridge on Interstate 75 is one of only 11 suspension bridges on the Interstate system in the entire country.

Fourteen percent of Michigan's major roads, which include Interstates, are rated in poor condition, and an additional 24 percent are in mediocre condition.

Vehicle travel on Michigan's major highways increased by 27 percent from 1990 to 2004 - jumping from 81.1 billion vehicle miles traveled in 1990 to 103.3 billion vehicle miles traveled in 2004. At the same time, total lane miles in the state increased by only four percent.