August 22 1960 / fromthearchive / Globe Staff photo by Philip N. Preston / The M.T.A. estimated 250,000 people were affected by the walkout of 4000 carmen at the beginning of rush hour. The sudden and unannounced strike over stalled contract negotiations left thousands stranded in Boston. The traffic jam in downtown Boston was the worst in the city's history as outgoing and incoming cars converged. Packed sidewalks added to the tie-up. The one-day's strike was estimated to cost over $6 million dollars to Boston merchants.