Trading in an Upside Down vehicle is not the answer. Not only do you loose money because of the accelerated depreciation, but usually people get a double whammy because they add the loss from the current car (Upside Down amount) to the loan of the new car.
This means that you stay in a cycle of debt that is higher that the vehicle is worth. Should you become financially unable to make the payments, say from a loss of a job, you will face another whammy trying to sell an Upside Down car and coming up with the balance.
Some new car loans are 68 months while older cars are up to 63 months. It is horrible to think of having car payments for 5 years or longer. An average new car is about $35,000. If you get tired of making loan payments, have problems with the vehicle, or loose a job, etc., you will probably owe more than the vehicle is worth for the many years of the note.
If your car is wrecked or stolen, the insurance company will not pay off your loan. In fact, the settlement may depreciate your car, making it difficult to come up with another car to drive.