For two decades, my homeward commute (when I’m driving, and these days when I’m also not working from home) has been the same: head south on Mass. Ave. to Newbury St., take the on-ramp formerly known as “exit 21”, and then the Mass. Pike west to Natick. This on-ramp has always been dangerous, with very limited visibility and no merge zone; I’ve narrowly avoided crashes innumerable times by either slamming on the brakes or flooring the accelerator. I didn’t avoid a crash once, many years ago, and got rear-ended by someone roaring down the ramp behind me as I stopped for heavy traffic. This two-mile stretch of highway is four lanes in each direction, with no shoulder; you can see the area I’m talking about on this map (from Google Maps):

This design made a modicum of sense in the original configuration of the Turnpike Extension, from 1963 until the introduction of physically separated E-ZPass lanes in the 2000s: with a mainline barrier toll at the Allston interchange as well as exit and entrance tolls there, westbound traffic was frequently slowed or stopped as far back as Comm. Ave. if not all the way to Copley Square. But when MassDOT implemented all-electronic tolling on the Turnpike in the 2010s, the Allston interchange was reconfigured to have three full-speed through lanes in both directions — which eliminated the bottleneck at Allston. To be clear, this change didn’t increase the capacity of the Turnpike; it simply meant that traffic was not stopped in Allston in addition to being stopped at the Copley (eastbound) and Newton Corner (westbound) lane drops at times of congestion. MassDOT is now engaged in a process that will hopefully replace the outmoded and wasteful Allston interchange, which was designed the way it was to support a connection to the never-built I-695 Inner Belt freeway.

The Prudential Center, one of the first major freeway air-rights projects in the US, was built in conjunction with the Turnpike in 1961–63. The John Hancock Tower and Copley Place followed in the 1970s and 1980s, and the state has long been looking to generate even more revenue from its valuable Back Bay real estate. Since late 2020, two air-rights projects have been under construction between Mass. Ave. and Beacon Street — with a third one under contract but yet to begin — and as a result there has been a lane restriction in both directions between Copley and Beacon St. to allow the construction crews to safely install the buildings’ foundations. After much hue and cry over how much of a traffic impact this would have, the end result has been … nothing. (Granted that traffic has been reduced somewhat as a result of the pandemic, but not so much as that.) With the bottlenecks through Allston and Copley already being limited to three lanes, the traffic capacity simply isn’t limited by the work zone — at least not any more than it is limited by the unsafe merges that were always there. Eastbound traffic still backs up at the Copley lane drop, and westbound traffic doesn’t back up until Market St. or even closer to Newton Corner. On the westbound side, there simply isn’t that much traffic entering at Copley Square or Mass. Ave. and exiting at Allston — that’s simply not a route that makes sense for most of the trips that could conceivably use it — so the traffic that takes exit 127 westbound is traffic that came from I-93 or points east, and without a toll barrier on the exit ramp, that traffic can queue along the whole length of the ramp without backing onto the mainline Turnpike.

This aerial photo shows the air-rights parcels (under-construction parcels shaded in purple, future parcel in green):

(I may be misremembering the parcel numbers, and didn’t bother to look them up, so they’re not labeled on the map.)

One of the most controversial aspects of the project to replace the Allston interchange (which is also supposed to include a bus/train station and significant new construction on the Harvard University-owned former railyard) has been the area called “the throat”, where MassDOT is trying to thread a two-track railway and twelve lanes of freeway (eight lanes of the Turnpike, four of Soldiers Field Road) in a very narrow stretch of land between the Boston University campus and the Charles River, without impacting traffic on the MBTA Worcester commuter rail line or on the Turnpike or on Soldiers Field Road during construction, and without any permanent structures in the Charles, and without unduly limiting use of the Dr. Paul Dudley White path, which parallels Soldiers Field Road. That section is highlighted in the map below:

Community advocates have largely recognized this as a fool’s errand, and contrary to the city’s and state’s climate goals to boot. Fixing the interchange and removing the viaduct through the throat, and of course building the new train station, are all recognized as positives, but even with a Federal Highway Administration waiver for limited shoulder widths, it has proved impossible to squeeze all of these roadways into the space allowed without either elevating one over the other or building into the Charles. Of course, the “impossibility” is a sham: it’s only “impossible” because both MassDOT (through the effort of former MassDOT secretary Stephanie Pollack) and the Department of Cars and Roads Conservation and Recreation have refused to countenance any reduction in freeway capacity. It is quite clear from the results of the current work zone that the Turnpike is two lanes too wide between Allston and Copley, and it would be a tremendous boon for safety and the environment if it was reduced to six lanes with full shoulders and safe merges at the entrance ramps. Likewise, although I do not have as much direct knowledge, the bottlenecks on Soldiers Field Road are all downstream, on Storrow Drive, especially at the Bowker Interchange and at Leverett Circle: Soldiers Field Road could stand to be just two lanes wide in this stretch.

These width reductions (24 feet on the Turnpike, 20 feet on Soldiers Field Road) would have a very limited impact on traffic, if DOT and DCR stopped their obstructionism, and the result would be a much cheaper, more constructable Allston project with bigger buffers between the freeway traffic and park users.