It helps to think of metro Atlanta’s transit matrix as being an in-process puzzle.

Some pieces have long been in place, such as the steel cross of the current MARTA system. Add to that the shapes of the various county transit systems and GRTA’s Xpress bus network. Together, they flesh out enough of the puzzle to allow glimpses into where things should head next on the road to enhancing mobility in metro Atlanta.

And there’s still a large box of pieces on a far side of the puzzle table. The challenge ahead for all of us will come in figuring out how best to add these elements toward a cohesive, effective, efficient whole. Friday night’s spectacular fire and collapse of a portion of I-85 illuminates the fragility and vulnerability of our undersized transportation infrastructure.

Getting to a better place will involve future lobbying, politicking and new T-SPLOST elections that may result – or even possible state funding. The promise of all that will be new transportation improvements – many of which have already been on planners’ radar for decades.

Next up in these big initiatives is the in-the-wings expansion of MARTA transit in the city of Atlanta. It’s powered by city voters’ November approval of a half-cent Transportation Special-Purpose Local Option Sales Tax (T-SPLOST) expected to raise more than $2 billion locally over 40 years. It’s hoped that federal matching funds could increase that to as much as $6 billion.

Any funding stream that large is sure to capture – and keep – the public’s attention in ways positive and negative. As a result, the city and MARTA cannot overlook that they will operate under an intense, at times-unforgiving spotlight for years to come.

This demands that both entities behave smartly and remain well above ethical or fiscal reproach in how they choose transit projects and subsequently pay for them.

For its part, MARTA, under CEO Keith T. Parker has greatly improved public perception of the agency and the services it provides. Parker & Co. have literally made the trains run more frequently, quickly returned bus routes to Clayton County after voters chose to join MARTA, and made other service improvements.

Better yet, MARTA’s enhanced fiscal discipline has gained fans at the Gold Dome – a place that had, historically, been deeply skeptical, if not hostile, ground for transit advocates.

Then there’s the city of Atlanta. Despite some positive moves by Mayor Kasim Reed that improved overall municipal finances, the city’s reputation has been battered lately by an ongoing federal investigation into allegations of contracting corruption.

And, more directly relevant to transit in the city and beyond, the Atlanta Streetcar’s vast underperformance to date has proven an irresistible lure for critics of both the city and transit.

The Streetcar, seen in the best light, suffers from being too far ahead of its time. Its current, dismal ridership can only improve if smart, longer-haul transit moves come next. The current, 2.7-mile loop perhaps now most useful to tourists could well see much-greater usage once it ties into future lines designed to move more riders more places.

Other cities have experienced greater success with light-rail or streetcar systems.

St. Louis has a two-mile streetcar loop now nearing completion that will connect a Decatur-like suburb’s main street with the existing rail network, a major museum and that city’s equivalent of Piedmont Park. It builds upon the MetroLink light-rail system that, to the consternation of critics, exceeded ridership projections when it began running in 1993.

Kansas City’s new downtown streetcar line has also initially surpassed rider expectations in that auto-centric city, although usage fell off as cold weather set in.

Atlanta and the rest of the metro can learn from these and other systems. What the city and MARTA do next will be closely watched by the entire region, and will influence other nascent transit expansion efforts.

Much of the current, areawide interest is no doubt driven by the private sector’s big, well-publicized moves to locate – or relocate – business centers closer to transit options. Business leaders attuned to their workforce’s needs are increasingly recognizing their workers want options that don’t involve crawling along crowded roads for long periods each day.

Astute elected officials have taken note, and begun to act accordingly. In North Fulton, State Sen. Brandon Beach, R-Alpharetta, has championed extending MARTA’s rail system further up Ga. 400. Gwinnett County is also seeing some renewed interest in expanding transit.

There will be debate over the merits – or not – of transit proposals in days to come. Such pressure-testing in the public sphere is often not a bad thing.

What should be a commonality among supporters and naysayers alike is a realization that we must do better in terms of enhancing our ability to move more people efficiently around this vast space we call home.

How well the city and MARTA deliver their piece of that puzzle will resonate far beyond Atlanta’s borders.