. >>> the mayor welcomes the opportunity to make changes at muni, ed ruskin plans to leave in august after serving in the role for eight years, more now on today's shakeup at the transit agency.>> reporter: london breed was straight to the point, about his resignation letter. >> clearly it is time to make a significant change, that is what we are proposing. >> reporter: that changes him leaving his post, announcing his resignation when his contract expires. >> i want to think the people of san francisco who rely on the public transportation system, and have been patient with us as we have tried to address what we know our real challenges in the city.>> reporter: it has become clear this is the right time for change he said, i'm extremely grateful to the sf mta board for for my day me -- providing me with the privilege to serve in this capacity, and to work with all of you. after a challenging week in the agency, some were forced to walk or take buses, because the metro service was interrupted when lines came down, causing a power outage, the day before that, 2 separate incidents, cau