FRANKFURT, Germany (AP) — Volkswagen is trying to reassure German customers worried about the future of their diesel cars by telling them they can trade in their new diesel if it is banned from the road by cities trying to meet air pollution limits. The company said Thursday that the guarantee applies to new cars bought from a Volkswagen dealer from April 1 through the end of the year, and would be good for three years. If the car owner is hit with a ban on driving at work or at home, the car could go back to the dealer for a non-banned model.