Mayor Bill de Blasio could not have set a higher goal regarding traffic fatalities on Wednesday, saying his aim is to “literally reduce fatalities on our roadways to zero.” Last year, 173 pedestrians were killed in New York City, and seven have already died this year. At a press conference where he was joined by victims’ family members, De Blasio announced the formation of an interagency working group to study the problem, which he said will be a “central focus” of his administration. Also, on Thursday, speed cameras will start issuing tickets instead of warnings, and the NYPD will begin increasing the number of officers assigned to its highway division by twenty percent. Other changes under consideration include lowering speed limits, redesigning streets, and increasing the number of red-light cameras. “There’s been an epidemic of traffic fatalities and it can’t go on,” De Blasio said. “The time to start change is now.”