From June 2-4 2014 MUNI workers participated in a sick out with hundreds of MUNI drivers calling in sick. This created large disruptions in MUNI service. MUNI workers returned to work on June 5th.
Timeline
June 2
"Muni did not provide specific figures on the number of operators who called in sick for their scheduled Monday shifts, but MTA spokesman Paul Rose said 400 of the 600 Muni vehicles normally on the streets were not in service during both the morning and evening commutes." [SF Chronicle]
June 3
"It was another tumultuous day for San Francisco commuters, as half the 600 drivers of buses, trains and cable cars who usually show up for work called in sick Tuesday, the outgrowth of an impasse in contract negotiations between management and labor.
The public transit system's worst labor disruption in decades could continue on Wednesday - even though an unusually combative Mayor Ed Lee has directed the city's Human Resources Department to investigate each worker who has called in sick.
The mass absence flouts a law that bans Muni employees from striking. But since it's a wildcat action, union leaders are emphatic in saying that they had nothing to do with making it happen and, therefore, cannot call it off." [SF Chronicle]
June 4
About 30% of MUNI operators called in sick on the third day of the strike. Word on the street is that the strike could continue until the end of the week.
Apparently though MUNI service improved: "Buses and light-rail vehicles, which had been spread across the city in a makeshift effort to haul as many passengers as possible Monday and Tuesday, returned to their regular routes, but the Municipal Transportation Agency still reported a serious shortage of transit operators reporting to work.
Cable car service was canceled, and only 440 of Muni's 600 vehicles were on the street. Those numbers were a steady improvement from Monday and Tuesday." [SF Chronicle]
Lawsuit from the city
"San Francisco City Attorney Dennis Herrera filed legal charges Wednesday with the state Public Employment Relations Board. He alleged that Transport Workers Union Local 250-A, despite taking a neutral position on a proposed contract vote, privately urged its members to defeat the tentative agreement, then "fomented and supported" an illegal work stoppage by encouraging operators to call in sick." [SF Chronicle]
Why is this happening?
"The sickout came amid displeasure over a proposed labor agreement that was the subject of a vote Friday [(5/30)] by Muni operators." Read more about it here.
"Transport Workers Union Local 250-A officials said on Tuesday that their workers had voted 1,198 to 47 against the proposed labor agreement that management offered them last Friday. This Saturday an arbitrator is scheduled to meet with both sides to resolve the dispute." [The Bold Italic]