Clean Cities Act This bill requires the Department of Energy (DOE) to carry out a Clean Cities Coalition Program. Under the program, DOE must make awards to clean city coalitions or nonprofit organizations for projects and activities that reduce petroleum consumption, improve air quality, promote energy and economic security, and encourage deployment of a diverse, domestic supply of alternative fuels in the transportation sector. DOE must also ensure that there are active coalitions working in all states, the District of Columbia, and the territories. In addition, DOE must provide technical assistance and training to the coalitions, provide opportunities for communication and sharing of best practices among the coalitions, and maintain and publish a centralized database of information about the activities and accomplishments of the coalitions.