Have to wonder though why the Turnpike authority in the early sixties did not specify an eight lane cross section all the way out to 128
Much of the Pike's Boston Extension was constructed adjacent to
very active railroad corridors & tracks. An 8-lane corridor plus shoulders would've drastically impacted those rail lines.
Historic note: Fred Salvucci's grandmother was evicted from her home due to the construction of the Boston Extension. This would be the same Fred Salvucci that would later become Gov. Dukakis' Transportation Secretary and the master architect of the Big Dig.
At the time the Extension was built, construction of the Inner Belt (I-695) was still planned, with an interchange in the area where Comm. Ave crosses the Pike. It was probably expected that much less traffic would use the part of the Pike west of that, since Rte 2 and the unbuilt SouthWest Expy (original I-95) would have been easily accessed alternatives.
Quite true. Had the inner Belt (I-695) & the Route 2 Connector been built, a fair amount of east-west traffic would've used those roadways instead of the Boston Extension.
That section should ideally be widened to 4 lanes, but it is probably not practical.
See above. Much of the Boston Extension abuts active railroad tracks.
One improvement that could be made would be to redesign the messy interchange with Rte 95/128 and Rte 30 now that the tollbooths are gone.
It's worth noting that some minor tweaks were done to that interchange, mostly on the Pike's end since those toll booths came down. Given the surrounding area & unlike the I-495 interchange in Hopkinton, I don't believe there's too much one can do with the Weston (I-95 (MA 128)/MA 30) interchange without totally disturbing the surrounding area. Not to mention that
traffic would still need to be maintained during the construction process.