How about something like this? You can opt to pay (e.g. hit a payment button inside your car) to enable manual, hands-on driving on a per-roadway basis. Otherwise you let the car drive in what it sees as the most efficient way, and pay nothing. When traffic problems are at their worst, you pay the most. Conversely, on an open road, no charges apply.<p>In addition, some multiplier involving driving conditions (rain, wind, proximity to other vehicles) and driver stats (driving record) comes into play.