Founded in San Francisco in 1954 by legendary structural engineer Professor Tung-Yen Lin (T. Y. Lin)—a world-renowned pioneer in prestressed concrete and seismic bridge engineering—TYLin (T.Y. Lin International) has evolved into an international multidisciplinary infrastructure consulting powerhouse. Operating as the flagship brand of the Global Infrastructure Pillar of Sidara (formerly Dar Group), TYLin employs over 3,200 engineers, transit architects, planners, and construction managers across more than 65 offices in the Americas, Asia-Pacific, and Europe.

In the railway and transit sector, TYLin is globally celebrated for its structural design excellence, complex alignment engineering, and seamless integration of heavy and light transit modes. The firm provides full-lifecycle engineering covering feasibility planning, environmental studies, detailed guideway and bridge engineering, traction power electrification, signalling interfaces, station architecture, and construction engineering and inspection (CEI). TYLin is a market leader in elevated transit guideways and long-span railway bridges engineered for extreme seismic zones.

Notable project references include the detailed design and engineering of the Panama Metro (Lines 1 and 2 elevated viaducts and underground sections), guideway structural engineering for the Panama Metro Line 3 monorail, the Miami International Airport (MIA) Mover Automated People Mover (APM), transit corridor integration on the Samuel De Champlain Bridge (incorporating Montreal’s automated REM light rail line), major capacity upgrades for the Chicago Transit Authority (CTA) Red and Purple Lines, the San Francisco Bay Area Rapid Transit (BART) extensions, and structural design for the California High-Speed Rail program.