As reported last week, tolls on the Pike, already scheduled to rise from $1 to $1.25 at the Allston and Weston booths, and from $3 to $3.50 in the Ted Williams and Sumner tunnels, may need to rise much more than that to cover the cost of the Big Dig.
Another quarter or two certainly adds up for frequent Turnpike travelers, but it is the sort of incremental tax that seems unlikely to become a major issue.
But if the increase is going to be much much more, maybe enough people will stand up in strong opposition to the increase and the increase becomes politically unacceptable. For a long time, many people who use the Pike frequently have said that a gas tax increase would be a more equitable way to pay for the Big Dig, and maybe the threat of it costing $5 or something like that to drive from Waltham to Allston could unify enough voters and legislators to make this happen.
As Elmer mentions on the misc.transport.road newsgroup, the tolls on the Turnpike encourage people to take Storrow Drive instead of the Pike, even when the Turnpike would be faster and more direct. The case could probably be made from an environmental viewpoint that we should not penalize drivers who are coming from the west and want to take the shortest, most direct route to the airport or 93S. Taking Storrow is easier on the wallet but it means more miles travelled and therefore more gas burned.