UPDATE: There will be an open house on the project this Thursday, June 6th from 5:30-7:30 p.m. at the South Lake Union Discovery Center (101 Westlake Ave N). Go, gander, shout your opinions in person!

Mayor Mike McGinn is in Pioneer Square this morning announcing that he wants to build a streetcar through downtown Seattle to connect the First Hill streetcar to the South Lake Union streetcar.

The announcement, while unsurprising, officially confirms what many suspected: That building a downtown streetcar beats out buses for commuting efficiency through downtown. By 2030, city officials estimate that transit will need to carry an additional 8,000 people per hour into downtown during morning commute times, which amounts to about 10 four-car streetcars or 150 new buses.

Eventually, McGinn also wants to extend the streetcar system to Ballard and the University District, and extend the First Hill streetcar into Pioneer Square (its current terminus is at Fifth Ave and Jackson St).

Of course, there's no money yet to build this downtown line (or any other lines), but McGinn spokesman Aaron Pickus says this is all part of the city's plan to be "shovel ready" for new lines before applying for federal grants or going to the public with another transit funding package.

From what I hear, city planners are looking at either running the downtown streetcar along First Ave or by creating a Fourth/Fifth Ave couplet, but the final alignment won't be identified until November.