This week's Question: Countries like the Netherlands have recently undergone trials of an automobile GPS system that uses a mileage-based formula to  calculate charges based on individual car trips. In particular tests, a  tabulation takes into account a car's fuel efficiency, the time of day,  and whether a route is a busy or less-traveled one. At the end of each  month, the vehicle's owner would receive a charge much like that of a cell phone bill, detailing times and costs of usage. Supporters of  these types of meters contend that the charges are fairer than current taxes like automobile purchase and registration fees; they derive from  actual use rather than mere ownership. If imposed, they could also  replace gas and vehicle taxes as well as tolls, or offer greater charges for vehicles with poor fuel efficiency. Opponents, however, dislike the  introduction of a new type of tax, and some critics have privacy concerns about the monitoring of drivers' locations.   What do you think? Is a GPS-based meter a promising model for cars?   RESULTS