Over the next nine months, metro Atlanta will engage in a debate over its transportation future. But in a larger sense this is really a debate over the region’s economic future.

Last month, a regional roundtable of 21 local elected officials approved a list of transportation projects to be financed by a 1 percent sales tax. This levy must be approved in a 10-county regional referendum scheduled for July 31.

Will we invest in the necessary and appropriate infrastructure to support future growth and provide a decent quality of life for our residents? Nothing short of that is at stake in this vote.

The good news is that the project list approved by the roundtable offers a remarkable new direction for metro Atlanta — one that would invest in transit in a balance with roads and begin to provide more mobility and choice to residents.

From a transit standpoint, here’s what’s on the list:

● Three new rail lines (the Beltline, Clifton Corridor and the I-75 Corridor to Cobb County) that will serve an estimated 40,000 new riders daily and provide 22 miles of new capacity;

● Significantly expanded regional bus service including a new high-capacity line to South DeKalb County, restoration of the Clayton County system, and expanded service in other parts of the region;

● $600 million in badly needed capital improvement investment in the existing MARTA system; and

● Planning and engineering money to lay the groundwork for the “next generation” of rail transit projects, including Gwinnett rail, 400 North heavy rail extension and Atlanta-Griffin commuter rail.

Taken together, transit projects account for 52 percent — or more than $3.2 billion — of the overall list. This is truly transformative, both in terms of the shift in funding emphasis to transit and in the magnitude of new investments in the region.

There is still plenty of funding for roads on this list — nearly $3 billion for some 125 different projects throughout the region. And this is on top of nearly $11 billion in road money that will be available over the next 10 years from traditional gas tax and related funding sources.

But the big story in next year’s referendum will be transit — and the fact that local officials have called for bold new approaches and investments.

This is really not a choice for the region, but a necessity.

Our region is projected to continue to grow — by some 3 million people in the next 25 years, to a total of 7 million. During this period, our region will become distinctly older, have far fewer households with kids and will be comprised of a growing number of residents interested in living where they have good access to where they work. That means they will want more transit.

Virtually every one of Atlanta’s major competitor regions — such as Charlotte, Dallas and Phoenix — are investing in transit to create a place that employers will want to invest in because of better access for workers to jobs.

The Atlanta region has reached a “tipping point” with respect to support for transit. One can see it in various poll and survey results. And one can sense it in the growing coalition of supporters that includes urban residents and suburban commuters, environmentalists and business people.

A clear majority of our residents want more and better travel options. This referendum is, above all, a giant step in that direction through its $3.2 billion transit commitment. We can’t afford not to take advantage of this once-in-a-generation opportunity.

Ray Christman is a former executive director of the Livable Communities Coalition of Metro Atlanta. Jim Stokes, former president of the Georgia Conservancy, is the coalition’s interim executive director.