In 1923, the city of Detroit and the railroad began a plan to build 22 grade separations; both parties agreed to share the cost.
This grade separation was agreed in 1890 after much litigation.
Traffic engineers usually refer to the latter as a grade separation.
The city also encouraged the railroads to build grade separation throughout the city.
Usually it is separated from other traffic by a concept called grade separation.
The bridge carries both road and rail traffic, without grade separation.
In September 2008 a contract was awarded to provide a grade separation.
The grade separation was completed for $142m in 7 months.
As such, there was an urgent need for grade separation.
The grade separation was completed in late 1941 - just nine weeks before the United States went to war - and cost $4.3 million.