Bold design for a car-free span over Fort Point Channel would reflect a forward-looking city

A rendering shows one of the possible designs for a span to replace the Northern Avenue Bridge.City of Boston

Wow.

That was my reaction Wednesday on seeing the latest renderings for a new Northern Avenue Bridge to link the Fan Pier/Moakley Courthouse wedge of the Seaport with the Financial District.

The old Northern Avenue Bridge had tons of character to go along with its tons of rusting steel and crumbling concrete — most of all the swing mechanism that, back in the day, allowed it to pivot so boats could pass through Fort Point Channel. It was a monument to old Boston and its gritty, working waterfront.

The new span, as envisioned by city officials, would reflect the kind of forward-thinking high-tech hub we aspire to be: smart, sleek, sexy, and green. The plans now on the table give priority to commuters on foot and bike, and people looking for a nice place to hang out. Boston has all but ruled out allowing single-occupancy vehicles and city buses on the bridge.

But with a price tag that could run to $100 million, even $120 million, can we afford our aspirations?

We should push hard for this bridge — and ideally it would be free of all but emergency vehicles.

We must make it easier to get around our flood-prone city without impeding efforts to reduce carbon emissions.

But as with so many infrastructure projects these days, it won’t happen without private money to leverage taxpayers’ dollars. And that makes things more complicated.

A basic design — something like the adjacent Evelyn Moakley Bridge — would be tens of millions of dollars cheaper, but as boring as much of the Seaport’s architecture. And chances are good that it would end up another noisy stretch of concrete and asphalt dominated by cars and corporate shuttles.

Thankfully, the city seems to have taken seriously the widespread calls to think about the Northern Avenue Bridge as more than a way to ease traffic into and out of the Seaport.

Without vehicles, the bridge could be another jewel in an open-space necklace that includes Fan Pier Park, Children’s Wharf Park, the Harborwalk on both sides of the channel, the Rose Fitzgerald Kennedy Greenway, Post Office Square, and Boston Common.

“You can see yourself on the bridge,” said Stacy Thompson, a member of the task force advising the city on the Northern Avenue project and executive director of LivableStreets Alliance, a transportation advocacy group.

No one would say that about the other channel crossings.

Thompson is part of a vocal contingent pushing to bar all vehicles from the bridge, a pledge the city has not made. They argue that the volume of traffic the new Northern Avenue connection could handle wouldn’t make a big dent in the Seaport’s congestion. They also say it makes more sense to add bus rapid transit on nearby Summer and Congress streets, to expand commuting options to and from North Station.

Others, including many businesses in the Seaport, argue that some vehicles should have access to the bridge — at least the shuttles that carry employees around the neighborhood. We can’t ignore this side completely. Here’s why:

Mayor Walsh, who also wants to build a new bridge to Long Island, has set aside $46 million in city funds for Northern Avenue. Boston also has $10 million in federal funds that can be used for the bridge, and has raised $2 million privately.

Where will the rest of the money — some $42 million to $62 million — come from?

City officials and task force members think more funds can be wheedled from the feds, but it seems hard to imagine the gap can be plugged without private money. Foundations focused on greener transportation solutions are likely to step up, but corporate cash will also be needed.

That could entail donations to cover construction costs, a new business-funded improvement district, such as the ones for Downtown Crossing and the Greenway, and other options.

I’m not sure, but I’d bet the corporate money would come with the condition that shuttles be allowed on the new bridge, even if there are logistical issues on the ramps at either end.

If that’s the price we pay to get the new Northern Avenue Bridge, I’ll take the compromise.

But you know what? Those shuttles had better be electric.