Seattle's new SR 99 tunnel
Seattle’s newest tunnel provides a direct route on SR 99 between the stadiums and the Space Needle. It is the largest double-deck highway tunnel of its kind in the country, and features modern safety and operations systems.
Know your new tunnel:
- Two miles long
- Two lanes in each direction, plus an eight-foot safety shoulder
- South portal near stadiums; north portal near Space Needle
- No mid-tunnel exits or entrances
- Currently toll-free; tolling will start as soon as summer 2019
- Learn how freight routes change with the new SR 99 tunnel
Using the tunnel video series
New intersections at the tunnel's north and south end
With new on- and off-ramps come new intersections. Our web post explains how intersections by the stadiums and the Space Needle have changed.
The tunnel’s south portal is just west of CenturyLink Field. On- and off-ramps in both directions connect SR 99 to the stadiums, Alaskan Way and Colman Dock along the waterfront, and downtown Seattle. Just to the east is the start of I-90 and connections to I-5.
Coming northbound on SR 99, the exit to downtown and Alaskan Way is the last exit before the tunnel. That ramp ends at new intersection of South Dearborn Street and Alaskan Way South (shown below). Drivers heading to southbound SR 99 from downtown or the stadiums can use Alaskan Way or First Avenue South to reach the new southbound on-ramp at this same intersection.
The tunnel’s north portal sits just east of Seattle Center. On- and off-ramps provide connections to nearby Denny Way, Dexter Avenue and Mercer Street, as well as routes to reach I-5.
Southbound drivers can take the off-ramp to Denny Way and downtown, which ends at the intersection of Aurora Avenue North and Harrison Street. From there they can head to Seattle Center (west), South Lake Union (east), or into downtown (south)
Drivers seeking to head north on SR 99 can use Aurora Avenue North or Harrison Street to reach the northbound on-ramp.
Three blocks of Aurora Avenue North, between Harrison Street and Denny Way, will be reconnected as part of the demolition project (see below). The approach to the Battery Street Tunnel will be brought up to grade and rebuilt, and John and Thomas streets will be reconnected east-west across Aurora Avenue North. Learn more about this work on our demolition page.
The highway inside the tunnel is two lanes in each direction. Unlike the Alaskan Way Viaduct's extremely narrow shoulders, the tunnel has an eight-foot shoulder in each direction for vehicles to pull over in case of breakdown or crashes. Long, gentle curves allow for safe sight distances.
The tunnel is built to modern earthquake standards and features smart systems that work together to keep traffic moving safely. In the event of an emergency, exits every 650 feet provide shelter and escape routes, while a state-of-the-art ventilation system assists first responders and fights fire and fumes.