A pilot program tests a recording and payment system based on miles driven.

Colorado is rethinking its 22-cents-per-gallon gas tax, which is less effective in generating revenue today as vehicles continue to gain better mileage per gallon.

The Denver Post reported that beginning in December, The Colorado Department of Transportation (CDOT) is rolling out a program that will try out a new way to raise money: requiring motorists to pay for every mile they drive.

The Road Usage Charge Pilot Program is set to run for four months and is recruiting 100 volunteers, who will record how far they drive and pay 1.2 cents per mile. No actual money will change hands in the experiment, but it aims to give CDOT a sense of how the system might work. One CDOT spokesperson told the Denver Post the system would be similar to how people already pay for electricity and water based on how much they use.

CDOT told the Denver Post it plans to provide three ways for drivers in the pilot program to track mileage: reporting and recording what the odometer shows or plugging a device into their car that tracks mileage either with GPS capability or without.