This is like a machine that it's always something you need to fix, to oil, to repaint, to clean and possibly to replace.

The Manhattan Bridge needed major repairs at a relative early age. The threat came from the very trains it was built to carry. Held in place by steel cables, the Manhattan has the advantages and drawbacks of a suspension bridge. One advantage, it can flex; one drawback, it can flex. That drawback emerged when the first subway train crossed. As the heavy cars pass, the bridge sways. One side dips, the other rises a full meter. Steel isn't made to flex. The relentless torsion snapped off beams, spanning the lower roadway.

The Manhattan Bridge was so neglected, the tracks finally had to be closed for repairs. In the 1980s, the city invested 2.5 billion dollars in a 3-decade program to overhaul its bridges. On the Manhattan Bridge, engineers installed heavy steel braces to stop the swaying.

注：聽力文本來源于普特