The Pennsylvania Turnpike has done a good job of laying the foundation for all-digital toll collection, to the point that more than 70 percent of all turnpike drivers now use E-ZPass transponders rather than cash.

Over the years the turnpike aggressively has marketed the transponders, created more non-stop gates at toll areas and, most important, created a toll structure that reflects the higher costs of collecting cash tolls. E-ZPass use now includes a discount of about 25 percent per toll, compared to paying by cash.

Recently the commission decided to implement its plan to eliminate all of the system's 76 toll booths by the end of 2018, in favor of a non-stop, automatic toll collection system through E-ZPass. It's goal, which seems feasible, is to have 85 percent of drivers pay by E-ZPass by 2018. It would use other means - billing drivers after recording their license plates, setting up pre-paid toll accounts tied to license plates or some combination - to collect from drivers who don't use the E-ZPass system.

The change is inevitable, given the technology and the advantages. It costs 20 cents to collect an electronically paid toll and $1 to collect a cash toll. But the E-ZPass also allows traffic to keep moving, reducing congestion and rear-end collisions at toll areas and reducing pollution from cars that are stopped rather than getting nearer their destinations.

Now, just as the commission has laid the foundation for automatic toll collection, it and PennDOT should begin the process of preparing for digital tax collection.

Highway taxes are collected primarily at the site of fuel sales. But as vehicle mileage continues to increase and technology moves toward electrically powered vehicles, the system of paying for highways inevitably will have to change. Taxes eventually will have to be based on a the number of miles traveled by vehicles rather than on the amount of fuel they use.

That means that a system, akin to E-ZPass, will have to be developed to record vehicle miles. To do so without revealing where a vehicle has been - which is certain to be a major privacy issue - transponders will have to be developed that record and send only the number of miles driven.

The future already is on the turnpike. But it's right around the corner on every other road.