sentences:  The Portland Transit Mall (formally named simply the "Portland Mall") was constructed by TriMet, the Portland metropolitan area's regional transit agency, in 1976–77 and opened on December 11, 1977.It was formally dedicated in March 1978.The mall comprises 5th Avenue, for southbound buses, and 6th Avenue, for northbound buses, and when first opened it involved the sections of those streets extending from West Burnside Street to SW Madison Street