They're less common than they used to be, but you can still see some semi-trucks sporting more than one license plate. Why?

Martin Rivera is sympathetic to truckers. His father-in-law, Igor Berlin, is an over-the-road tractor-trailer driver along the East Coast. Rivera knows it’s a sometimes dangerous and often thankless ...

You might have heard the term "jackknifing" with regards to semi-trucks, especially when they're in accidents. What is jackknifing, and how does it happen?