The $171-million, 700,000-sf structure will rise at the corner of 1st and Main streets, replacing the transportation agency's current headquarters at 120 S. Spring St. Mayne submitted two possible designs, one that would feature 15 stories and the other that would have 16 levels. Each design includes space for a large public courtyard.

Government leaders performed a worldwide search to choose the architect, noting that the building will stand across from City Hall and thereby be one of the most prominent projects in the entire city. Mayne, who was recently chosen to design the new federal building in San Francisco, beat out semi-finalists Rem Kollhaas of Netherlands-based OMA and Benedetta Tagliabue of Miralles Tagliabue in Spain.

Construction could begin next year, after a final design is completed and approved.