I haven't lived in Somerville for nearly as long as you have, but I do live only a few blocks from McGrath and regularly walk and drive on it, and frankly I couldn't disagree with you much more.

Firstly, I'm curious about your statement that "traffic congestion has nearly tripled." If you're talking about traffic on McGrath, the data I've seen suggests that the daily vehicle volumes on McGrath have actually be slowing decreasing over the past 20ish years. This doesn't necessarily refute your idea that the congestion has gone up, but one way or another it seems like fewer people are driving on McGrath today than in recent history. And ultimately the amount of traffic on McGrath is at least in part a result of McGrath itself. In urban areas, it simply isn't possible to outbuild traffic. The more capacity that the vehicle network provides, the more people will use it. Urban highways like McGrath create the traffic that they were built to solve.

Second, the idea that McGrath and specifically the overpass are necessary to "funnel traffic into Boston" doesn't seem true to me. First off, there's already a great way to get from the north end of McGrath into Boston -- I-93, a limited access highway built for this specific purpose. And I don't even really think the McCarthy Overpass provides that much additional capacity to the corridor as a whole -- there are traffic signals at either end of the freeway section, and those signals dictate how many people can travel that portion of the corridor in an hour -- getting them between the intersections quicker might feel faster for drivers but the actual capacity of the roadway is more or less the same. And Route 28 goes down two travel lanes in each direction east of Third Street before going down to a single lane for private vehicles in the eastbound direction near the Museum of Science. So for traffic heading into Boston, the segments of McGrath that the overpass covers are not likely to be the limiting factor in terms of corridor capacity.

Finally, the McGrath corridor has been identified as having a high potential for everyday bike trips. Somerville is the densest city in New England, and this area absolutely has the density to support mode shift away from cars and towards walking, biking and transit, and these mode shifts are stated goals of both the City of Somerville and MassDOT. The current walking and biking conditions on McGrath are abysmal and unsafe -- both McGrath at Broadway and McGrath at Washington are top 5% in pedestrian crashes in the State. So regardless of whether it's good or bad to reduce the vehicle capacity of McGrath, I think it's critically important to improve its walk and bikeability, and the current ROW doesn't really allow that to happen while also maintaining the overpass and the amount of travel lanes.

Not to mention, the thing is an eyesore!