original question: What type of surface is used by the runway at [San Francisco International Airport] with the width less than or equal to [61.0]?
answer: asphalt
answer type: Airport runway surface.
auxiliary information: San Francisco International Airport is an international airport 13 miles south of downtown San Francisco, California, near Millbrae and San Bruno in unincorporated San Mateo County. It has flights to points throughout North America and is a major gateway to Europe and Asia. SFO is the largest airport in the San Francisco Bay Area and the second busiest in California, after Los Angeles International Airport. In 2013 it was the seventh busiest in the United States and the twenty-first busiest airport in the world by passenger count. It is the fifth largest hub for United Airlines and functions as United's primary transpacific gateway. It also serves as Virgin America's principal base of operations. It is the sole maintenance hub of United Airlines, and houses the Louis A. Turpen Aviation Museum. SFO is owned and policed by the City and County of San Francisco, but is actually in San Mateo County. Between 1999 and 2004 the San Francisco Airport Commission operated city-owned SFO Enterprises, Inc., to oversee its business purchases and operations of ventures such as operating Honduran airports.
At the [San Francisco International Airport], which kind of surface is used by the runway with the width less than or equal to [61.0]?