Atlantans who pay attention to such things have been reeling from the news: We rank dead last for income mobility.

It’s one thing to start out low on the income scale. It’s far worse to be unable to move up.

If upward mobility is limited in metro Atlanta, as a high-profile economic study last month found, what should we do about it?

The study did not identify what causes low mobility here or elsewhere. It could only point to conditions correlated with low mobility, such as poor K-12 education and a large share of single-parent families. One much-discussed factor for Atlanta is physical mobility — people’s ability to reach workplaces, especially via mass transit.

Transit’s specific effect on income mobility in metro Atlanta is unclear. But it’s an intriguing question, particularly in light of last year’s failed T-SPLOST referendum.

As you may recall, the T-SPLOST would have raised $7.2 billion in 10 years for transportation, with half of the money tabbed for transit. Voters, weary from traffic but wary of the plan, rejected it.

T-SPLOST advocates and opponents debated how much should be spent on transit. The better questions were not “how much” but “what kind” and “where.”

To the degree our transit limitations hold back upward mobility, “what kind” and “where” remain key.

Poverty has been rising in Atlanta’s suburbs, where 87 percent of the region’s poor lived as of 2010. Combine that finding with the income-mobility study, and it’s likely many of people stuck at the bottom of the income scale live OTP.

For them, the issue is not the “last mile” connectivity to popular destinations that transit advocates usually seek. MARTA already goes to many places where the poor work, or could work. Rather, they lack “first mile” connectivity from their homes to MARTA.

Now let’s recall the transit projects on the T-SPLOST list. There was some money to maintain existing GRTA commuter bus service. There was also a hazily defined project linking MARTA’s Arts Center station to Cobb County: either “premium bus service” to Acworth or, if federal funds were available, a light rail line to Cumberland, barely OTP.

But two of the biggest transit expansions were decidedly ITP: the Clifton Corridor rail line, and a pair of streetcar segments along the Beltline. The T-SPLOST’s transit expansions largely would have been intown, and mostly in areas that are relatively well-off and already served by buses.

That’s not to say those projects are unworthy. They just aren’t the biggest priorities when the most congested roads, and most poor people, are elsewhere.

T-SPLOST’s backward priorities largely reflected the stubborn notion that public transportation should be a catalyst for economic development, and not chiefly a way to help people go where they already need to go but can’t.

Speaking to the latter, the free-market Georgia Public Policy Foundation has proposed the state spend $30 million a year to begin expanding fast, efficient bus service to the suburbs. It will release a more detailed plan later this month.

Does it seem odd that free marketeers have a plan to improve mobility — of both kinds — for the poor? It shouldn’t.

Income mobility is a goal across the ideological spectrum. Acting in a fiscally responsible way to help people move efficiently to jobs, when we don’t have lots of money to spend more dreamily, should be as well.