WASHINGTON, D.C. — Leadership at the National Transportation Safety Board (NTSB) shifted on Wednesday as Christopher Hart’s term as chairman ended on schedule.

NTSB Vice Chairman Bella Dinh-Zarr now serves as the agency’s acting chairman. Meanwhile, Hart will continue as a board member, with that term slated to end on Dec. 31.

Hart’s two-year term as NTSB chairman began in March 2015, and he served as acting chairman for almost a year before that. He has been a familiar face in the school bus industry, having spoken numerous times at national conferences. He also presided over NTSB’s on-scene investigation of the recent fatal school bus crash in Chattanooga, Tennessee.

In an interview with School Bus Fleet in 2015, Hart discussed other school bus crash investigations and the agency’s findings on seat belts, among other safety issues.

NTSB's five board members are nominated by the president and confirmed by the Senate for five-year terms. A board member is designated by the president as chairman and another as vice chairman for two-year terms. When there is no designated chairman, the vice chairman serves as acting chairman.

Dinh-Zarr began her term as a board member of NTSB in March 2015, and she was also designated vice chairman. Before joining NTSB, Dinh-Zarr served as a director for the FIA Foundation, an international philanthropy that promotes safe and sustainable transportation. Her career has also included positions at AAA, the National Highway Traffic Safety Administration, the U.S. Centers for Disease Control and Prevention, and the Texas Transportation Institute.