WSDOT and Sound Transit are adding high-occupancy vehicle (HOV) lanes to the outer roadways of the I-90 Mt. Baker Ridge and Mercer Island tunnels in both directions. This collaboration will make vital improvements for traffic flow on I-90 while preparing the center roadway for Sound Transit's East Link light rail line from Seattle to Mercer Island, Bellevue and Redmond. The I-90 tunnels were opened to traffic in 1989 with a full transverse ventilation system and 3% AFFF fixed fire suppression system, and the smoke management system improvements for the tunnels are of a vital importance for safe tunnel operation that includes loaded fuel tankers. The design team performed ventilation system tests, suppression system tests, live fire tests, Saccardo nozzle scale modeling tests and CFD analysis to upgrade the existing smoke management systems with minimum construction impact on tunnel operation. The new fire detection system is the key for timely activation of the smoke management systems. Multiple ventilation strategies were adopted to provide an emergency ventilation system capable of addressing smoke and heat from heavy goods or flammable liquids cargo fires including: sectionalization of the existing full transverse ventilation system for the westbound Mt. Baker Ridge tunnel; jet fans for the eastbound Mt. Baker Ridge tunnel and Saccardo nozzles for the Mercer Island tunnels.