References
If the toll is $.15/mile then some multiplication and unit cancellation gives you the equivalent gas tax:
$.15 | 15 miles $2.25
-------|------------ = ---------
mile | gallon gallon
This shows $.15/mile toll multiplied by a car that gets 15 miles/gallon. The miles units cancel, leaving you with $ per gallon. Basically multiply the toll rate per mile by the mileage to find the equivalent gas tax.
The intent isn't to tax fuel efficient vehicles, that's just the way it works out when everyone pays the same toll, but uses different amounts of gas. A gas hog pays the same toll, but spreads that toll out over more gallons consumed leading to a lower equivalent gas tax.
The cost per mile is in the material CAMPO posted on their WWW page. SH-130 and SH-45SE were both projected to cost around $30M/mile. I don't know if they are coming in over or under that figure now. SH290W, at the Y in Oak Hill, was projected to cost around $70M/mile, due to the large amount of elevated roadway.
--Steve Ravet, Libertarian

...I'm relying on the reputations of Vince, Steve Ravet, and Art DiBianca based on their prior successful work to make sure enough of the details (about the toll roads) are correct ....
--Wes Benedict, Executive Director, Libertarian Party of Texas