City driving mileage

How does the EPA estimate city driving mileage, rush-hour in Manhattan or midnight in Yeehaw Junction? What average speed is used, and how much time at dead stop per mile is assumed?

Here is an article that explains the testing procedures, although not in great detail it will give you some idea. It also explains what changes were made for 2008.

http://www.edmunds.com/insideline/do/Features/articleId=118986