CEO Joni Earl credited Kupersmith, who joined the agency in 2010, with making major contributions during her tenure.
"Celia's leadership has been invaluable. Her considerable operations experience helped improve our efficiency and the quality of our service," Earl said. "She also improved our budget process, served as a mentor to senior management and led the agency with a strong, steady hand during my unexpected medical leave of absence last year. She will definitely be missed."
Prior to joining Sound Transit, Kupersmith served as the general manager/CEO of the Golden Gate Bridge, Highway and Transportation District for 11 years and before that was executive director of the Regional Transportation Commission in Reno, Nev.
The agency is working on a recruitment strategy for replacing Kupersmith.