Cost analysis: a tank of gas or a traffic ticket

I pity those who've been stuck behind me on the roads lately. With gas prices topping $3.50+ per gallon, I've made a conscious effort to see how much gas I can conserve per tank. I've been laying off the accelerator and coasting at every opportunity, sometimes even shifting into neutral to reduce drag. So far it's worked. Last week I increased my gas mileage by over 2 miles per gallon. But this exercise spawned a cost analysis exercise recently.

While traversing Kissel Hill by the Lititz Library every day, I've figured out you can coast well into town if you let the vehicle go. But with a posted 25mph speed limit, letting the car go gets it up to 45mph. That made me question whether the cost of gas has increased to the point that accepting the traffic ticket would be more cost effective then a tank of gas.