Community leaders gathered Wednesday at the new Interstate 35 bridges over the Brazos River to admire an innovative project completed on deadline pressure.

Building the new $43 million frontage road bridges seemed like a big enough challenge when work began two years ago.

Nobody in the United States had ever built a bridge quite like them, with long steel girders supported by diagonal cables attached to towers. Engineers at the Texas Department of Transportation couldn’t even agree on how to pronounce the exotic hybrid design, which Europeans call “extradosed.”

But pressure mounted when Baylor University announced that it would build a riverfront stadium next door.

The project’s timeline shrunk from 27 to 24 months so traffic could get across the river to McLane Stadium by the opening date of Aug. 31, 2014.

The general contractor, Lane Construction, also had to finish the extension of Martin Luther King Jr. Boulevard past the stadium to La Salle Avenue by game day.

Now that project, called Loop 574, is substantially complete, and the frontage road bridges opened fully last weekend.

State, federal and local leaders celebrated the successful and timely completion of the project, which they said will enhance Waco’s transportation and development. The ceremony at the Texas Ranger Museum drew about 100 people and featured a parade of vintage cars across the bridge.

Waco Mayor Malcolm Duncan Jr. saluted TxDOT for listening to the “crazy idea” of community leaders who wanted a “signature bridge” to complement the city’s riverfront development.

State Rep. Charles “Doc” Anderson, R-Waco, compared the new bridges to the Suspension Bridge that opened in 1870 and cemented Waco’s status as a transportation hub.

“This says the same thing about the energy and forward-looking ability of this community,” he said.

The bridges are seen as a critical step in TxDOT’s plan to rebuild and widen Interstate 35 through Waco. The main-lane bridges over the river will be rebuilt as part of an as-yet-unfunded $300 million plan, but the frontage roads had to be built first so main-lane traffic could be rerouted during their construction.

A local committee worked with district TxDOT engineers to explore possible frontage road bridge designs that would be not just decorative but functional and economical. The bridge designer, AECom, suggested the extradosed design based on bridges its officials had encountered in Asia and Europe.

Gregg Freeby, director of TxDOT’s bridge division, said Hartford, Connecticut, is the only place in the U.S. with an extradosed bridge, but it is made of concrete, while the Waco bridges are primarily steel. He said TxDOT officials saw the Waco bridge project as a “laboratory” to see if the design could be used elsewhere in the system.

“Initially there was a lot of angst about it,” he said. “It was kind of out there.”

But he said the design has proved itself, and the Waco bridge already is being studied as a model for bridges in Texas and other states.

“I believe we will have other opportunities to build other extradosed bridges,” he said. “It is an economical way to do long spans.”

Freeby said the diagonal cables both support and provide lateral tension to the horizontal steel girders, effectively strengthening them. That means the girders can be longer and fewer piers are needed in the river.

The new bridges required only two piers in the river, compared with three for the old main-lane bridges built in the 1960s.

Compared with conventional suspension bridges, extradosed bridges have lower height requirements for the towers and are more economical, he said.

Evoking a tradition

Former Mayor Jim Bush, who attended the ceremony, said the design is modern yet evocative of tradition.

“It gives you a hint of the Suspension Bridge, but it doesn’t take away from the Suspension Bridge,” he said.

Both bridges include wide pedestrian walkways and overlooks. They will also have a state-of-the-art LED lighting system that can be customized for special occasions. While lighting will remain constant for passing traffic, accents on the towers, cables and sides of the bridge can be programmed to change colors, such as green and yellow on a Baylor game day.

A committee with representation from Baylor, the city and TxDOT will control the lighting.

Some Waco City Council members have pointed out that the new frontage road bridges block views of the river from the I-35 main lanes, which are several feet lower.

District engineer Bobby Littlefield said the main lanes will be rebuilt to the same height. He said the bridges already have been designed, along with the rest of the $300 million in planned improvements to I-35 through Waco, but funding has not yet been identified for any of that work.

Randy Hopmann, director of rural and urban engineering for TxDOT, said he is hopeful that state and federal leaders will find a way to fund the work.

“TxDOT is committed to Interstate 35, and the commitment is there from our partners,” he said. “It’s certainly an important project.”