My first night following a garbage truck was on a sweltering Thursday in July 2016. After many rejections, I had persuaded a driver to let me follow him for a shift. He was taking a big chance: Workers can get fired in an instant, but he was willing to risk his job to take me into his world. What I saw opened the door to a far more complex investigation than I’d anticipated, one that involved dozens of interviews over 18 months with drivers, helpers, regulators, owners and experts; combing through thousands of pages of civil and criminal records; reviewing hundreds of documents obtained through public-records requests; and building a database of federal truck inspection records.