Oregon ran a pilot program in 2006 and 2007 that fitted 300 cars with GPS receivers, which kept track of the cars' mileage. The receivers also kept records of when the cars were on the road, noting whether they traveled during rush hour or not. When the drivers went to several specially-equipped gas stations, they paid a mileage tax based on how far they had driven and when they drove, rush hour being more expensive than the wee hours.