Amid the super-scaled changes spawned by the replacement of the old Transbay Terminal, it’s oddly heartening that the first segment of the new transit center to be completed is a taut work of functional infrastructure.

The structure is the new bus bridge that crosses Howard between First and Second streets. Fourteen steel cables hold up the north end of the ramp that will give buses from the East Bay a straight shot off the Bay Bridge to the new Transbay Transit Center.

Within the transit center’s $2.26 billion budget, a $57 million ramp is small change. And because the new facility doesn’t open until sometime next spring, the bridge, with its concrete tower flanked by roadways, isn’t yet in service.

But even viewed solely as sculpture, the robust span holds its own amid the emerging, emphatically urban scene.

The single tower itself is stark, unadorned concrete with angled slots where the cables are attached. The cables fan down in stiff diagonal lines, gripping the horizontal “ribs” that connect the two sides of the busway.

The structure has been likened to the eastern span of the Bay Bridge, which opened in 2013, but the only similarities are the presence of a central tower and diagonal cables with a white sheen. The newcomer isn’t a suspension bridge, the type we’re accustomed to in the Bay Area. It’s a cable-stayed span, the roadway held rigidly in place — a type of bridge more often seen in Asia, though Boston’s cable-stayed Zakim Bridge has been turning heads since 2003.

“As a bridge designer, I’m always a little surprised to hear the comparison,” says John Eddy, who leads the infrastructure practice in the firm Arup’s San Francisco office. “One had nothing to do with the other.”

Nor does the bridge aspire to be a visual symbol of the transit center, which will feature a rooftop park above an undulating white metal skin. It’s there because an underground train box for future rail service to the center means that when the overhead ramps approach Howard Street from the Bay Bridge, there’s only a compact spot where they can be given the support they need.

So instead of standard thick columns, as is the case where the bridge ramps cross Folsom Street, there’s a single narrow tower. On either side, narrow ramps flare around it heading north and south — the horizontal beams that connect the ramps are spaced about 15 feet apart, allowing wide shafts of light to reach Howard Street below.

The oppressive underpasses you’re used to? Not the same thing at all. In fact, below the bridge there will be a two-block-long park on the south side of Howard Street.

The bus lines also slice across Howard at an angle dictated by property lines, and with a slight tilt to the east. Both elements add kinetic energy to the visual show, something passersby will sense even if they can’t quite pin down why.

“The curved alignment was baked into the design, but it’s cool that it turns. And I love the fact that we were able to split the deck,” Eddy confesses. Overall, though, “we knew if we added ‘architecture,’ it would be cut out (because of cost pressures). So we were on a mission to keep it simple.”

Given the setting in an increasingly busy part of town on a now-prominent block of Howard Street where two towers will rise alongside it, I wish the bridge were more polished. The tower’s concrete form could be detailed, or chamfered at the top. Illumination above the roadbed would have been welcome after dark — not Bay Lights gaudy but a simple tracing of the silhouette.

Yet the perfunctory finishes jibe with the straightforward task at hand.

To see what I mean, take in the view from Second Street.

The background is silvery and sleek, the city of tomorrow sprung to life in thin metal and glass. In the foreground is the matter-of-fact masonry from the past, low-slung and nonchalant.

And in the middle, we have a self-confident celebration of getting from point A to point B. It has no desire to be an icon. These days, that’s a virtue in itself.

Place is a weekly column by John King, The San Francisco Chronicle’s urban design critic. Email: jking@sfchronicle.com Twitter: @johnkingsfchron