Los Angeles County's transit agency is wrapping up meetings with the public tonight on its plans to bring a dedicated busway to a 12-mile stretch of Vermont Avenue from South L.A to Los Feliz.

The bus lines that currently run along Vermont have among the highest transit riderships in the county, second only to that for Wilshire Boulevard. The $425 million dedicated busway would speed along the buses, but given the Vermont corridor's popularity, why isn't it slated for a rail or subway like Wilshire?

The dedicated busway envisioned for Vermont could some day be converted to light rail or a subway, but that may not happen for 50 years. The Measure M sales tax approved by county voters in 2016 provides just enough funding for the busway rather than rail, at least not until after 2067.

That long timeframe has transit watchers wondering why Vermont, a prime candidate for rail investment, doesn't have higher priority, especially since the Los Angeles County Metropolitan Transportation Authority spends billions to serve fewer riders elsewhere.

The answer has much to do with the way L.A. County funds transportation investments.

What does the Vermont project involve and who will it serve?

The corridor runs from 120th Street in the south to Hollywood Boulevard in the north, traveling through the heart of the city and crossing neighborhoods in South L.A., Exposition Park, Koreatown and Hollywood.

Beyond its popularity with bus riders, the corridor connects to multiple rail lines, employment centers like the University of Southern California and Hollywood and serves dense, low-income neighborhoods that rely on transit.

With 45,000 daily weekday boardings, transit ridership on Vermont is nearly equal to that of the entire Gold Line light rail, which is more than double the length of the corridor.

Metro ridership projections for the busway proposals range up to 75,000 daily boardings, which would be higher than any of Metro's rail lines, except the Red and Purple Line subways.

A faster, higher-capacity subway or light rail on Vermont connecting to the regional rail system would lure even more riders, who could switch from slower bus service on adjacent streets or choose transit over driving.

What's the current plan for Vermont Avenue?

Metro is studying two options for the dedicated bus lane running either down the right side of the road or a combination of right and center lanes.

The busway could also have other features to speed it up, like priority at stop lights, curbside fare collection, boarding through all doors and fewer stops.

An L.A. Metro presentation shows the two concepts for a dedicated busway on Vermont Avenue. LA MTA

Metro has budgeted $25 million from Measure M for the project and $400 million from other sources. The current timeline has the project breaking ground in 2024 with completion between 2028 and 2030.

But only after 2067, when obligations end for projects approved under Measure M, would funding be freed up to build a rail line on Vermont.

After hearing community feedback, and at the request of the Metro board of directors, the agency is studying and refining options for some kind of rail to pursue at that later date — or if unanticipated funding becomes available to move on it. The options include two for light rail, one for a streetcar and three subway alternatives.

Metro hopes to narrow down the rail alternatives to three for further study.

Why wasn't the Vermont corridor originally planned as a rail project?

The short answer: rail is expensive and L.A. County has limited resources to invest in it.

While the Measure M sales tax increase is expected to raise $120 billion over 40 years, hard choices still had to be made about which projects the money should fund.

Metro arrived at the final list of Measure M projects by asking representatives from different parts of the county to prioritize the projects they wanted based on available revenues, and a rail line on Vermont didn't make the cut.

Part of the calculation in choosing which projects get funded is that Measure M needed to appeal to two-thirds of county voters, the threshold to pass a sales tax increase. To do that, the measure had to fund projects that satisfied voters from all over the county, not just those in the central urban areas that most use transit.

So projects were not strictly chosen based on which lines would have the highest demand and greatest return on investment, but rather on appealing to voters across the county who would be footing the bill.

Taking such factors into consideration in picking which projects to fund is driven in part by how transportation projects are now funded.

L.A. County, and pretty much all local governments, now pay for transit with local sales taxes approved by voters. Back in the 1970s, the federal government covered up to 80 percent of major transit investments, but the share has dwindled since.

In the infrastructure plan proposed by the Trump administration last year, the roles would be reversed with the federal government putting up a 20 percent match and local dollars funding 80 percent, and only for major projects that won approval.

More than 80 percent of L.A. Metro's funding comes from voter-approved county sales tax increases, four of which have been passed: Proposition A in 1980, Proposition C in 1990, Measure R in 2008 and Measure M in 2016. About 10 percent comes from the state and 7.5 percent from the federal government.

Tonight's meeting on the Vermont Avenue project runs from 6 p.m. to 8 p.m.

at the EXPO Center, Roy A. Anderson Recreation Center, at 3980 Bill Robertson Lane.

Vermont Corridor Presentation May 2018 by Metro Los Angeles on Scribd