bigpicture and Arlington the problem with all of this is the T's reach and reliability. Its nice to tell people to eat their peas because its good for you. The problem is, voters will rebel if they're being told they have to eat rotten peas (the MBTA). You will see a referendum on the ballot to repeal this law, just like what happened with indexed gas tax increases, if the other side of the equation isn't solved (the T's reach and reliability again).
Now some would argue you need money to improve the T and a $5 congestion charge helps in that regard. Sure, but from the start the people you're trying to force onto the T will still be dealing with a system not built to handle cross town and multiple connection trips. You have to solve that issue BEFORE trying to hit people with a significant fee (again, $1250 per year out of pocket is a lot of money for working class people based on 5 days a week 50 weeks a year). Otherwise the combination of people who need to drive due to factors outside of their control (T can't easily get them from home to destination) plus those who are now dealing with broken down trains and unreliable busses while pension costs continue to skyrocket will consign this policy to the trash can after the next election.
Its not a bad idea. Your heart is in the right place. But, what's dooming this effort is the T itself. You'd also have to be damn sure the traffic utopia you describe actually occurs (weekday commutes are like current Sunday commute) because cutting commuting times by 5 minutes isn't going to matter to enough people IMHO.
Yes, all of this.
I get the theory, I get the incentives, I get all of it. A congestion tax would definitely make sense in the perfect world. But pushing people to substitute away from driving can be very burdensome when driving's substitutes often don't work very well, and there's little indication that they will improve. This is way more pertinent for commuters into Boston than Boston residents.
What separates transportation from other behaviors that can influenced by targeted fees is that (a) transportation is a necessity; and (b) transportation networks and infrastructure are largely centrally planned by government and unresponsive to economic incentive (while private behavior is responsive to economic incentives).
Point (a) separates congestion from something like smoking, because smoking has no intrinsic value. If everyone up and quit smoking today the overall economic engine of society would not suffer. Smoking has no (significant) redeeming qualities, so limiting it is (pretty much) only a good. Congestion is not like this. If traffic went away totally, a whole lot of economic output and valuable activities would be lost.
And on point (b), think of the difference between a carbon tax and a congestion fee. Upon implementation of a carbon tax, for example, the private sector would, through the powers of innovation, ingenuity, and profit-seeking self interest, come up with new low-carbon sources of energy and production. Through the private sector, the economic incentives created by a carbon fee would directly bring about the carbon substitutes we need. In the face of a congestion tax, the private sector simply can't do this. By their very nature, public transportation networks need to be planned and executed by a central planning authority. Since central planning authorities don't really respond to economic incentives, increasing the economic incentives to improve public transit isn't all that efficient. So a congestion tax would likely increase carpooling (which would be good and doesn't need government action), but it wouldn't necessarily help public transit.
As an example of this, the prevalence and success of Uber and Lyft clearly demonstrate that there exist substantial economic incentives to create and expand alternative transportation networks as a substitute for individual driving and car ownership. But these incentives have not made public transit better.
Also, an important thing to remember is that places that have benefited from congestion taxes (e.g., Singapore, London) have MUCH better public transit networks than Boston does, so the alternative substitutes to driving exist and are better.
And City of Boston reports that list stats pertaining to Boston's transportation mode share look at Boston residents, not Boston workers. For example, from Table 7, 48.4% of Fenway residents walk/bike to work and 28.6% take public transit BUT from Table 6 97.9% of Fenway workers are not Fenway residents and 71.4% are not even Boston residents. I have little doubt that a congestion tax would not affect Boston residents nearly as much as it would commuters. But commuters are important! Someone like Michelle Wu doesn't have a single constituent who commutes into Boston, so of course she's going to advocate for policies that benefit Boston residents (her constituents) at the expense of commuters. That doesn't mean that those policies are a net win for overall welfare.
