Are the expressways entirely to blame for Detroit's decline? If the expressways were never built, would the exodus from Detroit have been prevented?

Let's go back in time before the expressways to the days of the interurban. Many Detroiters were drawn to live outside the city because of exposure provided by the interurban. Let's say that instead of building expressways, an extensive interurban system was built. Would this have been less of a means for exodus?

I propose that the exodus from Detroit would have occurred regardless of the expressways and regardless of the interurban. Detroiters would have left if they had to leave on a donkey down a dirt road.

Detroiters didn't leave because of a failure of Civic Planning. They left because there was a demand for their housing from blacks that were moving into Detroit from the South coupled with the availability of cheap land outside the city. And, unlike New York or Chicago, there was not enough commercial activity to make living there advantageous.

If an expressway was built through lower Manhattan, it would still be a densely populated city because it is the largest city in the most prosperous country on Earth and is the main financial and commercial hub of the planet. Reduce it to one industry, import millions of blacks from Haiti, and watch the people flee the city... by subway.