Car debt is piling up for consumers, according to a Bloomberg News report. The outlet found that the amount of negative equity, or the amount that debt surpasses a vehicle's value, is building up. This has led many car owners to show up at lots underwater, which is also known as "upside down," as they try to trade in their debt-burdened cars. The situation has emerged against a backdrop of rising interest rates, with the average new-car interest rate hitting 6.9 percent in January, up from 4.3 percent a year earlier, according to Edmunds.