High in the wicked folds of the western Sierra Madre, Mexican transportation officials have launched one of the most ambitious road-building projects in history — an experiment in social engineering as much as a structural one.

Across a landscape of yawning ravines and sheer-sided ridges so rugged that locals call it el Espinazo del Diablo — the Devil’s Backbone — the Mexican government is laying down a $1.5 billion “superhighway” that promises to exorcise centuries of isolation and bring an economic boom to one of the country’s poorest and most troubled regions.

When the 140-mile toll road opens as soon as late 2012, it will cut drive time between the interior city of Durango and the Pacific port at Mazatlan from seven hours to 21 / 2, conquering the Sierra’s unholy topography with 62 tunnels and 135 bridges.

More important, Mexican officials say, by completing a modern transportation link between the Gulf of Mexico and the Pacific Ocean, the highway will bring wholesome economic development and the rule of law to a place dominated by some of the country’s biggest dope growers and drug gangsters.

At the heart of the endeavor is the Baluarte Bicentennial Bridge, uniting the states of Durango and Sinaloa with a gravity-defying ribbon of concrete 1,321 feet above the Baluarte River. Completed this month, it is the highest bridge in the Western Hemisphere, the second-highest in the world and highest structure of its kind (cable-stayed bridge) on the planet.

So high is the Baluarte’s road deck that the Eiffel Tower could fit beneath it, or two Washington Monuments stacked end to end. With its long white cables and graceful towers rising 587 feet at opposite ends of the precipice, it may be the most breathtaking structure built in Mexico since the pyramids went up at Teotihuacan circa A.D. 100.

“This is a symbol of the prosperity we want for Mexico, a symbol of the Mexico of the future,” President Felipe Calderon declared at the dedication ceremony for the bridge.

That the Baluarte was built by Mexican engineers was a special point of pride, he said — proof that the country stands with the industrial giants of the world.

But there is ample reason to worry that Mexico’s superlative road could also serve as a super-conduit for drug trafficking.

With Calderon nearing the end of his term-limited, six-year presidency, the highway project is also emblematic of the legacy he wants to leave: one of economic stability and infrastructure modernization, not the savage drug violence that has left 50,000 dead since he took office.

For the president and other officials here, it is taken as a matter of course that the superhighway will bring a reduction in crime and lawlessness, by giving young men an alternative to working for the cartels. Much of the marijuana, heroin and methamphetamine sold on U.S. streets come from the farms and labs of the western Sierra Madre, a place that has long defied the civilizing intentions of government social workers and of missionaries before them.

“Infrastructure means jobs, infrastructure means development, infrastructure means progress toward a more just and prosperous Mexico,” Calderon said in his speech. “By opening up these opportunities, we shut down other activities we don’t want.”

But just as the highway will make Durango and other states in Mexico’s northwest interior attractive to foreign companies looking to build manufacturing plants, it will drive up the area’s strategic importance for the traffickers, who often smuggle their U.S.-bound cargo in legitimate commercial loads.

And it will link two places that are already roiling with cartel violence. Last year, there were 307 homicides in Mazatlan, making it Mexico’s seventh-most-violent city per capita, while Durango was the fifth deadliest, with 474 slayings, according to recent tallies.

Since April, investigators in Durango have pulled 282 bodies from more than a dozen mass graves in and around the city, where the dominant Sinaloa cartel has been fighting off incursions by various rivals, including Mexico’s ascendant criminal power, Los Zetas.

Now, local officials hope transportation engineers can accomplish what police and politicians have not, and bring security to the region with growth, not more guns.

“The best way to fight crime and eliminate poverty is to create jobs,” said Francisco Gutierrez, the top economic development official for the state of Durango. “This is the most important project in all of Mexico right now.”

Pros and cons

Gutierrez has been traveling the world in recent months to promote the new highway, and already the effort appears to be paying off. In November, Chinese firms signed deals on seven new investment projects in Durango totaling more than $220 million in mining, chemicals and auto-parts manufacturing.

U.S. car-parts maker Delphi is adding 3,700 jobs in Durango this year, Gutierrez said, and a Chilean mining and forestry firm is pouring in $150 million in new investment. A Spanish company wants to build one of the world’s largest solar-energy farms in the state.

Durango’s cost advantages appear to trump security concerns for many foreign investors. The average wage in the state is $13 a day, one of the lowest rates in Mexico, and when the superhighway is in place, the Pacific port at Mazatlan will be perfectly positioned for growing trade with Asia.

And yet, development experts say that there is no definitive research proving that better infrastructure reduces crime.

“All kinds of things travel on roads — both desirable and not so desirable,” Jordan Schwartz, the World Bank’s lead economist for Sustainable Development in Latin America and the Caribbean, said in an interview.

“To suggest that better infrastructure leads directly to the rule of law would be naive,” he said. “On the other hand, it is easier to intimidate, co-opt or destabilize an isolated community than one that is employed and connected.”

But others see a clear path to social progress with the new road. In Concordia, the county seat on the Sinaloa side of the bridge, teacher Beatriz Moran said she thought the new highway would help persuade young educators from urban areas to take jobs in rural mountain communities, knowing that they wouldn’t be stuck there and could easily go home on weekends.

“Right now, the kids in those towns only go to school through sixth grade because there aren’t enough teachers,” Moran said.

Jose Eligio Medina, the county’s top official, dreams of adventure tourists and hikers exploring the mountains of Sinaloa — a place that the U.S. government now urges American travelers to avoid. “This road is going to change everything for us,” Medina said, already drawing up plans for a restaurant and overlook at the bridge.

‘It didn’t seem possible’

When the first surveyors and engineers reached the bridge site five years ago, it was a four-hour ride on horseback. “We stood at the edge of the canyon and looked across, and it didn’t seem possible,” said engineer Carlos Zamundio, inviting a reporter to walk the newly completed span and peer into the sucking abyss below. “It was like putting together a puzzle, one piece at a time.”

Tradeco, the Mexican firm that built the bridge, had to put 15 miles of dirt roads into near-vertical canyons just to get equipment to the construction site, where 1,300 laborers were employed at the project’s peak.

“We had to build an entire village down here,” said Salvador Sanchez, supervising engineer on the project, speaking in his office at the bottom of the gorge.

Not a single worker died, he said.

In contrast, during a reporter’s trip to the bridge site, there were two trucking accidents on the old highway, one fatal; and at several locations along the route, the large, lumbering vehicles had to stop completely at tight curves, backing up to allow other drivers to squeeze by.

Sanchez said the new highway will go through — rather than over — the Devil’s Backbone, maintaining a consistent 5 percent grade, even on the Baluarte Bridge.

Made of high-grade, pre-stressed concrete, the bridge’s four-lane roadway is held up by bundles of suspension-mounted steel cables. Each five-eighths-inch strand can support more than 80 tons, and when banded together in bundles of up to 46 cables, they can absorb huge earthquakes as well as massive loads, he said.

“You could park heavy trucks on it from one end to another and nothing would happen,” Sanchez said. “It’s ready for anything.”