As fuel prices rise, gas tax receipts drop, and money for roads and bridges dries up - Gas prices are soaring. That's the bad news.But as they soar, motorists drive less, and that produces some benefits: less air pollution and less congestion. That's the good news.And then there's the bad news about the good news. The federal gas tax is levied on a per-gallon basis. So the less people drive and the less gas they use, the less the federal government collects from gas taxes. So it is that recent record high gas prices have produced record low gas tax...