Have you been toll-jacked on the new Chisholm Trail toll road in Tarrant County?You have if you have entered the toll road at McPherson Road and exited at Farm Road 1187. Or if you have entered at Sycamore School Road and exited at Alta Mesa Boulevard.And there are other places where this could happen to you.The North Texas Tollway Authority advertises a tolltag rate of 16.16 cents per mile on the new road. But a drive from McPherson Road to Farm Road 1187, a distance of 3.2 miles, will get you a toll charge of $2.08 instead of the advertise rate, which would be 52 cents. A drive from Sycamore School Road to Alta Mesa, about one mile, will get you a charge of 74 cents instead of the advertised 16 cents.The NTTA designed the Chisholm Trail such that there are three “mainlane toll gantries” strategically placed on the 27.6-mile road, along with 24 ramp gantries. However, there are about 19 locations on the toll road where drivers can usually enter or exit it in both directions. If the NTTA really wanted to charge for use of their toll road based on the distance you actually drive on the road, they would need to have about 70 ramp gantries instead of only 24. NTTA calls their tolling policy and practice “influence-distance-based tolling,” which is jargon for the longest distance you can travel between main tolling points determines the toll charge. Not having tolling equipment at all locations, NTTA charges by how far you could potentially drive in a given section of the road that falls under the “influence” of a mainlane toll gantry.At Sycamore School Road, for example, there is a ramp gantry for entry northbound on the toll road. But there is no ramp gantry at the northbound exit onto Alta Mesa. So, the NTTA system does not know if you have exited at Alta Mesa. It just assigns an “estimated” charge of 74 cents to your tolltag account based on how far you might have gone. Strange math, but it works for them. NTTA’s design for the tolling system extracts the maximum amount of money from toll road users. In other words, they knew they would be toll-jacking some, if not many, of the users of the road. They knew that for many users the effective toll rate would be much more than 16.16 cents per mile. Some might conclude that NTTA’s tolling practices are not right; that they are, on the face of it, discriminatory and inequitable. We can’t make those judgments here.Just be aware that you can be toll-jacked on the Chisholm Trail toll road. If you are, there is nothing you can do about it but pay up! And if you don’t have a tolltag, the charge is 50 percent more. Another happy thought: We are assured that the Chisholm Trail toll road is “a true Fort Worth road.” William L. Humm lives in St. Francis Village, just outside Fort Worth’s southwest city limits.