ST. PAUL (AP) — Two bridges that, for now, span the Mississippi River side by side are more than just old and new crossings of the heavily traveled Highway 61 in Hastings. They are symbols of an aggressive push in Minnesota to deal with deteriorating bridges after an eye-opening tragedy.

The skinnier steel truss bridge — long identified as a worrisome structure — is being demolished a section at a time now that two lanes of a state-of-the-art concrete bridge carry the load. By winter, all four lanes will be open.

As these projects go, the swap happened in a flash once state transportation officials determined the old bridge had been pushed to its limit. It was originally scheduled to be replaced starting in 2018. The project moved ahead with haste following the collapse of the Interstate 35W bridge in Minneapolis.

The city’s residents had grown leery of the rusting bridge and are ecstatic about its $130 million replacement, Mayor Paul Hicks said. “They’re proud of how it looks and that it is new and that they don’t have to worry about traveling over a rickety old bridge,” he said.

Bridge safety remains a topic of concern nationwide as aging structures take on serious signs of wear. A new Associated Press analysis of federally collected data shows that thousands of bridges coast-to-coast have multiple red flags.

More than most places, Minnesota has a heightened vigilance around bridge conditions since the I-35W bridge buckled during an August 2007 rush hour — a disaster that killed 13 people. In response, lawmakers raised the state’s gas tax to finance a 10-year bridge construction program focused on tackling those with deep-seated problems. Some $1.2 billion has gone into the effort so far, according to the Minnesota Department of Transportation.

The campaign has helped to roughly cut in half the starting-point list of 172 state bridges deemed structurally deficient, fracture critical or both. Among the remaining bridges, 27 were determined to need only routine maintenance in the near term. A few others have private owners.

A bridge is typically labeled “structurally deficient” if regular inspections uncover significant deterioration such as advanced cracking in concrete or steel components. The rating often leads to weight restrictions and increased monitoring and maintenance. “Fracture critical” is applied to bridges without multiple backup features, meaning that if one critical component failed, the entire structure could give way.

In the years since the I-35W collapse, dozens of Minnesota bridges, including some managed by local governments, have undergone significant rehabilitation or outright replacement. Many were simply closed. Still more will be fixed or torn down before the current campaign ends. Some, like the Hastings bridge, leaped years ahead on the construction schedule. Along the Mississippi River alone, six Minnesota bridges will have been rehabbed or replaced by 2018.