 By the 1920s, there were over 400 industries operating on Detroit's east side.However, the combination of the city's haphazard streetplan, the expansion of large factories, and the substantial network of rail tracks conspired to slow traffic within the city, particularly in the east-west direction.In 1923, the city of Detroit and Grand Trunk railroad began a plan to build 22 grade separations; both parties agreed to share the cost.