Regarding Overpasses

Over the course of the next few posts, I’m going to attempt to break down my proposal for the Mass Pike Realignment into bite-size chunks. After being asked a few questions regarding the feasibility of extending currently dead-end streets near the BU across the Pike and into Lower Allston, I decided this would be the perfect place to start.

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As it currently stands, a vast swath of Lower Allston is cut off from Allston proper and the remainder of Boston by the chasm that is the Mass Pike and the MBTA’s Worcester Line. To access the commercial district along Commonwealth Ave, the B branch of the Green Line, or downtown Boston, residents must take a detour to the only practical crossing at Cambridge Street.

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Demand for this crossing is high. Jobs, education, restaurants, transit, entertainment, and myriad other amenities require Lower Allston residents to trek out of their way every day. After crossing at Cambridge Street, there are only two north-south streets that are practical to reach Comm Ave and the Green Line; and they are narrow and vastly over capacity.Image

This demand is not only one-way. Not only do Lower Allston residents need to return to their homes at the end of the day, but there are many attractions in the neighborhood and beyond that encourage those from the south to trek north. Access to the Mass Pike, Harvard and Central Squares in Cambridge, the massive redevelopment currently under construction at Barry’s Corner, Herter Park for its scenic beauty and canoe rentals, and the Allston Public Library all reside on the far side of the Pike. The same two streets are used for reverse travel as well.

If only there were some way to shorten this trip and reduce overcrowding on Linden Street and Harvard Avenue…

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Dead-ending at the abandoned Beacon Park rail yards, Malvern Street, Babcock Street and Agganis Way (itself an extension of Pleasant Street) have the potential to triple the current capacity on this North-South journey while slashing trip times.

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The maps that precede this one were made primarily from a pedestrian viewpoint. But drivers can not be forgotten, after all, this projects genesis is rebuilding a highway. So lets take a look at a pretty common trip: from the entrance/exit of the Mass Pike in Lower Allston to around Babcock Street on Comm Ave. That is, everyone going to or from the Pike from Allston, BU, Kenmore, Brookline, parts of Brighton, and possibly the Longwood Medical area and beyond. Any car exiting or entering the Massachusetts Turnpike from the south must cram through the tiny streets of Allston Village.

In the 1.4 Miles it takes to go this roundabout route, one encounters seven traffic lights. If an overpass were added at Babcock Street, this trip would be cut by more than half, to less than 0.6 Miles, all while bypassing the ultra-congested heart of Allston Village. But that only benefits drivers, coming from afar on the turnpike.

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From the top floors of some homes in Lower Allston, one can see the Green Line running down the center of Commonwealth Avenue. And yet to get to it, one must walk far out of the way across Cambridge Street. Once across that overpass, your lowly pedestrian may either choose to take their life in their hands and make a legal yet extremely dangerous crossing at Linden Street** (as shown), or go even further out of their way to Harvard Ave.

Starting at the intersection of Empire and North Harvard Street to the MBTA stop at Packards corner, the current walk is nearly a mile. If an overpass were built at Malvern Street, that same journey would be reduced by a third of a mile, to just around 0.6.

**A crossing is legal if it is more than 300 feet from a marked crosswalk. Linden Street is nearly 400′ from the nearest crossing, meaning that despite the DOT dropping Jersey Barriers and proposing a fence to discourage crossing here, it is perfectly legal and within your rights. 720 CMR 9.09

In recent years, the city has made some great strides to improve cycling facilities. Bike Lanes on Comm Ave and around the neighborhood have vastly improved the experience of cycling downtown. Of course, long before the lanes were striped, Allston has had a wonderful, carfree way to bike downtown via the Paul Dudley White bike path, at least theoretically.

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If your proverbial cyclist was to start at Packards Corner to take the bike path downtown, they essentially have two choices. Either risk 1.1 miles on the right hook and dooring prone Comm Ave to the nearest overpass at BU Central, or 1.3 miles on the the equally deathalicious Cambridge Street. Building an overpass at the end of Agganis Way cuts that trip down to a mere half mile.

 

So extending these streets would be unquestionably good for the area. It would reduce trip times for automobiles, cyclists and pedestrians. It would drastically reduce the amount of traffic crawling through Allston Village, not to mention air pollution from all those idling vehicles. But the question remains, is it feasible? Many people have noted that in this section, the railroad tracks and highway are at grade, directly at ground level. This is true, however as luck would have it, this grade descends from Commonwealth Ave towards the Mass Pike, considerably so in the last block between Ashford Street and the tracks.

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AGGANIS WAY —— 100′ Run, 7′ Rise (7% Grade)

At Agganis Way, BU has constructed a retaining wall next to the tracks, that is by visual estimate at least twelve feet high. Above, I have used the terrain feature from Google Earth to model a bridge from this location. While GE is not entirely accurate, it is close enough for these purposes. As you can see in the picture below, taken from Buick Street, Agganis Way (where the road curves out of view at the top of the photo) is considerably higher than the adjacent tracks.

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Some quick background on my bridge models. Interstate Highway standards mandate 16′ of vertical clearance, and (not that it matters for local streets), a maximum 7% grade. To make things a bit harder on myself, I instead used CSX railroads recommended minimum vertical clearance for double stack containers, which is 22’6″. To account for the margin of error in Google Earth terrain, I made the clearance at least 23’6″. In short, the bridge’s I’m showing are higher than necessary. The bridge itself is three feet thick.

Getting back to Agganis Way, thanks to the retaining wall, the grade to climb is very short, starting roughly at the end of BUs 33 Agganis Way dormitory tower. Below is a (very) rough rendering of how it could appear from street level.

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BABCOCK STREET —— 230′ Run, 14′ Rise (6% Grade)

Moving west to Babcock Street, we have another bridge with no problem to get up and over the railroad and any other at-grade structure. As you can tell in the photo below, from Ashford Street, Babcock slowly descends to near level with the tracks, meaning that a bridge starting in this location already has considerably less height to climb.

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The only complexity in constructing this overpass would be relocating the loading bays for some BU services, seen at the very rear left of the above picture. The fire exits seen on the right would also have to be moved or otherwise accommodated. In the grand scheme of the project, these issues are relatively minor. Seen below another rough rendering from approximately the same location.

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MALVERN STREET —— 270′ Run, 13’6″ Rise (5% Grade)

The final potential crossing I examined was Malvern Street. Like the two previous sites, a decline from Ashford Street makes the start of the bridge already higher than the tracks and highway it has to cross.

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A bridge at Malvern Street is no problem, however the site has a few challenges. unlike the previous two examples, Malvern ends at Ashford Street instead of the tracks. This means that a taking would be required, and the small one story building at the left of frame above would have to be demolished. In addition, Malvern Street is narrower than either Babcock St or Agganis way. Narrow streets are certainly not unique in Boston, and this issue could be mitigated by making the road either one way or removing on-street parking. However, as is the case with Babcock Street, these issues are relatively minor, and hardly unheard of in similar construction.

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I believe I have stated it previously, but I am not a traffic engineer, or an engineer of any kind. I don’t have survey equipment or the tools to 100% accurately take measurements on this scale. However, with the resources available to me, I see no reason why MassDOT could not construct overpasses in these locations as part of the realignment project. The effects on traffic reduction and load spreading would be incredible. Access between Lower Allston and Comm Ave would be vastly improved. In the scope of rebuilding a large interchange, three overpasses are hardly going to break the budget. Since these new overpasses would be used to spread traffic to and from the turnpike, it is firmly within the scope of this project.

At the very least, MassDOT needs to send an engineering team here to determine exactly why, or why not this can happen. No is not an answer, facts and figures are.Image