The latest round of public meetings for the Westside Subway Extension begin tonight at 6 p.m. at the Los Angeles County Museum of Art as Metro officials are finishing up work on the draft environmental impact study/report (DEIS/R) for the project.

There are four other meetings scheduled between now and July 1. Here’s a press release with the time and locations of the meetings.

The DEIS/R is a key document required by law. First and foremost, it must consider all of the basic questions about the subway — where it may be located, how it will be built and what the impacts of the project will be and how those might be mitigated.

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But there’s more to a DEIS/R than that. The document also must justify the need for the project. In the case of the subway extension, the DEIS/R has to go beyond that: it must also make the case as to why the Federal Transit Administration (FTA) should potentially contribute billions of dollars from its New Starts program to help pay for the project.

Some of the statistics that will be presented to the FTA are among the most interesting material in presentations Metro officials have put together for the five public meetings.

First, let’s quickly review where the project stands. At this point, there are five basic routes being studied.

It is important to understand, however, that the only funding in place at this time under the long-range plan adopted by the Board of Directors of Metro is for the first two alternatives — a subway line that extends down Wilshire, veers south to Century City and then back north to Westwood. Alternative 1 would terminate near Wilshire and Westwood boulevards. Alternate 2 would continue west just past the 405 freeway and end near the VA Hospital.

So the real choice as to what to build now is between alternate 1 and 2. Which will it be?

The FTA has certain thresholds it considers when deciding whether to pony up federal dollars for a project. That list has expanded and the weighting of the criteria has been changed under the Obama Administration to include things such as a project’s environmental benefits, livability and potential to create economic development.

But one key criteria remains: cost-effectiveness, which considers ridership and time savings by passengers in relation to a project’s cost. And the higher the ridership, the more cost-effective a project is.

The slides below show that Alternate 2 would get more riders — or boardings, in the language of the DEIS/R — and also does better in the FTA’s cost effectiveness ratings.

The Source does not own a crystal ball (we want one, but it must be solar powered) so we’re not going to guess which alternative Metro staff will recommend this fall — after the DEIS/R is released this summer and the public has the chance to comment on it. At this point, the only thing that can be said for certain is that Metro is applying for federal New Starts funding for the subway and that alternative 2 performs better by the federal government’s standards.

Ultimately it will be up to the Board of Directors to pick an alternative and then to launch a final environmental impact study and the preliminary engineering of that alternative. If all goes by schedule, it remains very possible for there to be a groundbreaking on the project in 2013.

The presentations also have loads of other interesting tidbits about the subway project. To wit:

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•Building the subway from its current terminus at Wilshire & Western to the VA, would cost about $4 billion or $453.6 million per mile. Those are, of course, estimates. For the sake of comparison to light rail, the six-mile Eastside Extension of the Gold Line that opened last year cost about $150 million per mile, including a 1.7-mile tunnel. For the Wilshire corridor, Metro staff and the Board of Directors determined that a subway was better than light rail because subway trains can be longer and carry more people.

•Every time I hear someone from outside the Westside question the subway’s worthiness and cost, I want to use a giant laser pointer on the slide above that shows how having a subway helps people from across Los Angeles County get to the Westside in a speedier fashion. The time savings is, in my words, extremely significant.

•Over 300,000 people travel into the Westside every morning, making it the second-largest job center in the county. First is downtown Los Angeles.

•It is still essential to understand that under Measure R and Metro’s long-range plan, the subway would reach Westwood by 2036. It will take Congressional approval of the 30/10 Initiative — which includes federal loans and access to other federal financing — to get the subway to Westwood sooner. The current 30/10 plan calls for the subway reaching Westwood in 2017.