According the SF Examiner roads sometimes need to diet in order to become healthier. This means shifting emphasis from cars to pedestrians and cyclists by reducing traffic lanes, widening sidewalks, adding bike paths and greening medians. These road diets are long-term investments for the neighborhoods which they service. Road diets can decrease the number of cars, increase the number of pedestrians, improve safety conditions, reduce collisions, increase demand for restaurants and store-front businesses and generally improve the conditions of the neighborhood. Not surprisingly, City transportation officials say San Francisco has put more roads on a diet than anywhere else in North America. These projects and their results have been observed on Divisadero Street corridor, San Jose Avenue, Eddy and Ellis streets, Valencia Street and Folsom Street. Business owners and residents in these areas laud the new security pedestrians feel when crossing the street, the more leisurely pace of cars and cyclists and te improvement in the overall atmosphere and value of the neighborhood. Although not everyone is completely convinced, most people agree that the renovations add value to a neighborhood.
Sources:
http://www.sfexaminer.com/local/transportation/2012/08/road-diets-used-tool-reclaiming-neighborhoods-san-francisco