Linthicum joined SANDAG as the division director of engineering and construction when the agency consolidated with the Metropolitan Transit Development Board in 2003. Linthicum also spent 23 years at Caltrans, the last 11 as the deputy director of construction. He played a key role in many of the region's significant transportation projects, including the Mission Valley East Trolley extension, numerous highway projects, and the seismic retrofit of the Coronado Bridge. As director of mobility management and project implementation, Linthicum will serve as a member of the SANDAG management team, which consists of the executive director, chief deputy executive director, general counsel, and directors of the other four agency departments (administration, finance, land use and transportation planning, and technical services).