As the average length of a new-vehicle loan has increased to nearly six years, according to credit tracker Experian, so has the number of buyers who trade in a vehicle on which they owe more money than it’s worth. This is known as negative equity or being “upside down” on a vehicle. For example, if a car has a trade-in value of $10,000, but the owner still owes $14,000, the negative equity is $4,000. But what if you want to get rid of that vehicle?