Overview: In 2018, Italy's Morandi Bridge collapsed, killing 43 people.

For 50 years, the iconic bridge had withstood the elements and stress from ever-increasing traffic.

NOVA investigates what went wrong and explores other bridge collapses across the United States.

How can new engineering techniques make bridges safer and prevent such tragedies?

DVD Verdict: Focusing primarily on August 14th, 2018 when the Morandi Bridge in Genoa, Italy, collapsed, sending vehicles and tons of rubble to the ground 150 feet below and killing 43 people, 'NOVA: Why Bridges Collapse' is a very compelling investigation into a phenomenon that happens all around the world.

Witnesses said the bridge was struck by lightning during a thunderstorm before it crumbled, though lighting alone should not have felled the bridge. Preliminary investigation points to a combination of poor design, questionable building practices and insufficient maintenance.

The Morandi Bridge, finished in 1967, is named after the civil engineer who designed it: Riccardo Morandi, who died in 1989. Before its collapse, it stretched 3,878ft, connecting the A10 motorway toward France and A7 to Milan. Popular for both commercial traffic and local vacationers, the bridge formed an arterial connection between France and Italy.

The bridge was very much a signature Morandi piece. The cable-stayed bridge deck was made from reinforced concrete. The cables linking the towers to the deck were covered in concrete.

Like Morandi’s 1957 design for the General Rafael Urdaneta Bridge in Venezuela, the trestles of the bridge formed a double V: one of the Vs carried the roadway beam, while another one, upside-down, supported the upper tie rods.

On the morning of the incident, Genoa was hit by a fierce thunderstorm. Just before noon, a 300ft section of the highway collapsed, falling almost 150ft to the ground.

“I saw the bridge collapse in front of my eyes; the debris from the collapse landed 20 meters away from my car,” Davide Ricci, who was driving nearby at the time, told Genoese newspaper Il Secolo XIX. “It felt as if electricity was traveling from above downward, as if one of the beams had been struck by lightning.”

According to Angelo Borrelli, Civil Protection Department chief, the collapse took approximately 36 cars and three trucks down with it. Motorists on the bridge weren’t the only ones at risk; apartments and houses built under the bridge were crushed or had to be evacuated.

As hundreds of volunteers and professional emergency workers searched the wreckage for people, still-hanging sections of the bridge creaked ominously overhead.

The death toll stands at 43. In the days after the tragedy, mounting public anger has led to a search for causes: Was neglectful maintenance, shoddy workmanship or poor design to blame for the collapse?

For those seeking answers, the problem isn’t finding one possible solution. It’s determining which of the bridge’s many faults finally caused it to collapse.

Find out more about how further investigations have revealed more thoughts about the bridge's collapse, and how other bridges have suffered the same fate in this brand new PBS documentary 'NOVA: Why Bridges Collapse.' This is a Widescreen Presentation (1.78:1) enhanced for 16x9 TVs.