Commenting on correspondence to officials about the Mass Pike polls, John made these good points:
On the larger question of the effect of tolls on driver behavior, I think you have to consider the possible effect of diversion of traffic off the Turnpike onto local roads when tolls are increased. This, like the interaction between tolls and T fares, is hard to estimate without the use of computer models, and even then the results may not be dramatic.I think he's hit the nail on the head.
On time-varying tolls, I support that, although it would be good to seem some analysis showing that it encourages drivers to "spread the peak" rather than divert onto local roads. Unfortunately, ours is the only corridor into Boston where tolls are charged on the highway as opposed to just the bridges.
If you want to shape transportation behavior in the region, you have to think comprehensively about the interrelationship among modes. And, before you consider significant changes to one mode, you have to model the effects on the other modes.
Whether the changes end up being dramatic depends on whether the objective is revenue change or behavior modification. It may be that meaningful decrease in motor vehicle commuting -- where mass transit is currently available -- is going to need a combination of sharp increases in the cost of commuting by car, particularly during peak hours, and improvement in mass transit service.
And, steps will have to be taken to mitigate the effects on local streets.