SEATTLE, HERE ARE SOME OPTIONS BEING CONSIDERED FOR THE VIADUCT

As you know if you live in the Seattle area, there are plans to shut down the Alaskan Viaduct, and now some options have been revealed, and those options being studied are:

• A four-lane viaduct extending from South King Street to Bell Street, where it would rise above ground and connect to the Battery Street Tunnel through an elevated interchange similar to the current one. It would be smaller than the current viaduct. The concept assumes handling some trips on a reopened waterfront streetcar line and a new streetcar route to First Hill and Capitol Hill. It also would add bus lanes on eight downtown streets and adding a northbound lane and a "managed lane" -- possibly tolled -- on Interstate 5. Estimated top speed: 50 mph.
• A four-lane viaduct extending from South King Street to about Lenora Street, where it would drop to street level and connect on the surface to the tunnel via Elliott and Western. The idea assumes streetcar lines connecting the International District to Seattle Center as well as to First Hill and Capitol Hill. The structure would have one level for traffic, have a park on top and space below for offices or retail, to pay part of the cost. Estimated top speed: 40 mph.

Both elevated options assume conversion of Mercer Street to two-way traffic between I-5 and Seattle Center.

• A four-lane, two-mile tunnel bored underground between South Royal Brougham Way and Harrison Street, first carrying traffic under Western Avenue and Post Alley. The alternative assumes streetcar lines on the waterfront and to First Hill and Capitol Hill, a northbound transit lane on I-5. Surface traffic would follow Western Avenue and the former viaduct corridor. Estimated speed 50 mph.
• A shorter four-lane tunnel, dug from above ground between South King and Pike streets, connecting to the Battery Street tunnel under Western and Elliott. This assumes expansion of a park and ride facility in Lake Forest Park, 10-minute "Rapid Ride" Metro bus service to Lake City, added lane capacity on I-5, transit lanes on nine streets and streetcar lines to First Hill and Capitol Hill and to Seattle Center via First Avenue.
• A "surface" traffic option shifting traffic onto Alaskan Way and improving capacity of several downtown streets in addition to streetcar service to the waterfront and First Hill and Capitol Hill. The option would add 16 new traffic signals on Alaskan Way, four more on Western and Elliott near the connection to the Battery Street Tunnel and five on Aurora Avenue north of Denny Way. It assumes a "managed" lane on I-5 and two-way traffic on Fifth Avenue downtown and on Mercer traffic to Seattle Center. Estimated speed: 30 mph.
• A second "surface" option, similar to the first but with a two-block elevated section between Stewart and Lenora as well as two new streetcar lines. It assumes capacity on two more lanes of I-5, more transit service on downtown streets, expanding vehicle capacity on nine downtown streets and two-way traffic on Fifth Avenue downtown and on Mercer traffic to Seattle Center. Estimated speed: 30 mph.
• A third "surface" option similar to the second but with waterfront traffic handled using six lanes on Alaskan Way and Western Avenue. Estimated speed: 30 mph. With all three "surface" Third Avenue would be restricted to transit traffic downtown and 10-minute Metro "Rapid Ride" service is assumed on Aurora Avenue, West Mercer and from West Seattle.
• A partially lidded trench dug from above ground between Yesler Way and Union Street that would distribute traffic to and from the Battery Street Tunnel on the surface on Elliott and Western avenues and through several signals. It would provide four lanes of traffic in each direction on two levels and would have walls along open portions. The highway would be elevated between Stewart and Blanchard streets. It also assumes two new streetcar lines, two-way Mercer traffic to Seattle Center and more transit service on eight downtown streets as well as new lane capacity on I-5. Estimated speed: 40 mph.

(Source)