As the rising number and popularity of food trucks push them into the food mainstream, region by region, problems with local legislators and police reacting to new situations, and brick-and-mortar restaurants fearing competition, have to be worked through, in some cases creating significant business uncertainty. Chicago long held the distinction of being the only city in the United States that did not allow food trucks to cook on board, which required trucks to prepare food in a commercial kitchen, then wrap and label the food and load it into a food warmer. In 2012, under pressure from food truck owners and supporters, including the University of Chicago Law School, regulations were changed to allow on-board cooking, however, controversially, food trucks are required to park 200 feet away from any restaurant, which virtually eliminates busy downtown locations.