Perhaps,at first,they'd only do it on Interstates and other major roads.If so,they could easily do it in the same way that they collect tolls in the Northeast...with a transponder that you attach to your windshield that communicates with a receiver on the highway.
Most of them that I've seen require you to go 15 MPH as you pass the receiver,but one I saw (in NJ,DE or MD..can't recall which) allows you to do 55 MPH as you're passing.
The ones in Houston, Texas work at +80 mph.
They have those in Illinois for the toll roads. The little doo-dad gets pinged at the toll and your 'account' gets debited. You use a credit card to replenish the account in pre-paid amounts.
So, maybe all the roads in Oregon will become tolls then.
Hey, TOLLS FOR TROLLS!!!
(my apologies to those lonely Freepers in Oregon)
Those TollTag/EZPass transponders work up to 160mph - at least the ones here on the Dallas-area tollways do. (Someone with a bike went through a toll zone at 160 and his tolltag read correctly - not me! Someone in a Mustang went through one at 132mph and his tag read correctly, too.)
The ones here in Atlanta work at 85-90 mph apparently on our only toll road. Which is already paid for I might add way ahead of schedule, but those booths are still collecting quarters.