If this is true, then 65 percent do have access to vehicles. Lets subtract out the number of people who are too young or too old to drive that live in the City. The numbers for houses with cars suddenly look pretty good. In addition, the people who have cars most likely have more disposable income.
I don't see a lot of people on the bus or waiting for one on Gratiot carrying TV's from Costco. If you don't have a car and want to make a big purchase, you are going to coordinate your trip with a family member or friend who has one. The nature of retail has changed. It is no longer 1940, M-1 will only go up to New Center.
Regarding the parking at Hudson's. Yes there is parking there. Is there a lot? Well not after you subtract out the thousands of workers who carpool and park there every day. While the spots are there, the capacity is already full so assuming that the parking will be used by shoppers is foolish when the stores open at 9-10, but the office workers get there before 8. Staples bought Silvers and moved it to the eastern edge of Downtown for a reason: Parking.
What is the CBD's best market? Those who are there already. Office workers and residents need to be able to keep these places going and that is the market you should be chasing.
What many fail to realize is Downtown Detroit's retail market is fairly healthy when you compare it to most large cities in the United States. New York and Chicago are definitely not a normal retail environment. See Toledo, Cleveland, Columbus, Indy, Buffalo, and Pittsburgh and you will find the only one with a more healthy retail environment is Pittsburgh, but it is only marginally more healthy. MPS has a decent amount of retail downtown, but remember these folks are stir crazy and
locked in a habitrail for 9 months a year. Heck Detroit's CBD is even more healthier than places like Royal Oak, Birmingham, Plymouth, or Wyandotte when you adjust for the food court for drunk yuppies and hipsters factor.
Shopping patterns have changed drastically since 1940, everywhere. You cannot go backwards but change is inevitable. The big question is how do we improve what we have based upon current conditions? Having a big goal is great, but be willing to accept baby-steps to get you there.