We did vote on, and approved, a constitutional amendment allowing for such tolling after much debate in the prior legislative session. This wasn't a topic snuck through out of the blue.
It isn't double-taxation for a couple of reasons:
1) The gas tax (even after returning the 1/3rd that is shamefully siphoned off for education) doesn't come close to funding all the maintenance and new road projects the state needs. It barely covers maintenance right now, partly because inflation has raised costs while the tax amount hasn't risen. We benefit by inflation shrinking the bite of the tax, but it also reduces the funds available for roads.
2) These tolls are for new roads only, or new expansion of existing roads (with the existing portions remaining free.) So no one currently using a route will have to pay to use it, and people will have the CHOICE of whether to pay the toll on the new roads.
That is actually a more conservative approach to funding, because instead of everyone being forced to pay a tax for something they may not want or use, only those who actually want to use this road will pay for it. The risk for cost overruns also shifts from the gov't to the toll firm's investors, who are making a calculated risk that enough persons will see the tolls worthy of the faster or more direct trip.