Andrew is exactly right, this is more of a legal/permit question rather than a design question, every city has its own set of laws and regulations which dictate sizes and dimensions of parking spaces and turnarounds, I would check with the planning department and see if you can find someone in the planning department to walk you through the city standards and then see if there is any restrictions or variances for you particular site. Most city planning departments have people willing to help if you ask nicely, and with the downturn in the building markets they might have more time to help with your questions.