General Infrastructure

stick n move said:
Interesting. I do like that they all include a left turn onto 93 north, because I feel like most ppl that enter the circle do so only to go around it and back to get onto 93 north, so if you give drivers the ability to just turn left onto the ramp that should drastically decrease the amount of people either going to the new intersection or rotary.
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Because I always approached getting on the highway there from Southie and never Dorchester, I never noticed that you can't take a left from Columbia eastbound to get on 93N. I agree, that would be a major reduction in cars going to the rotary if they could pull it off.
 
I am surprised because one important benefit of a rotary is that you never have cross over traffic to take a left where it may be dangerous
 
FK4 said:
Anyone know if there are any movements afoot to put Revere Beach Parkway on a diet? It's always been such a ghastly road to me, and that third lane seems to unnecessary. It could actually be a pretty parkway if they eliminated both 3rd lanes and put in some trees, but I never hear any discussion on here about this particular DCR deathtrap.
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Kind of? There's efforts going on to rework Wellington and Sweetser Circle - which are both pretty significant, but not a broader corridor thing.

While I don't drive the road that frequently, the core road issue to my eyes seems to be a few absolutely terrible intersections that crush throughput and distort the view of how much roadway capacity is needed.

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To pick the single worst example:

At present you need 3 lanes towards 2nd St not because there's 3 lanes worth of free-flowing traffic or that you should need 3 lanes to move that number of cars down the road, but because the intersection is so broken that you need them for literal car storage, as especially going EB it's frequently a 3/4mi long 3-lane wide queue that already backs up into Sweetser + further breaks it, and would likely gridlock all the way back through Santilli + towards Wellington if you cut it to 2.

You could almost certainly slash a lane off the entire stretch through there if you could find a way to make the 2nd St intersection less hopeless. Would have been better to work on before the Anthem building went up, but I do wonder if you could get the geometry improved meaningfully enough to improve anything with taking the auto body shop to the north.
 
stick n move said:
Interesting. I do like that they all include a left turn onto 93 north, because I feel like most ppl that enter the circle do so only to go around it and back to get onto 93 north, so if you give drivers the ability to just turn left onto the ramp that should drastically decrease the amount of people either going to the new intersection or rotary.
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This is the one and only thing I think we should emulate from Florida specifically for the Columbia/93 exit:
flroida int unedited.jpg

Minus the straight-through lanes because in our case they're ramps not frontage roads
Florida intersection.jpg

Of course it'd be on a smaller scale and we can eliminate the slip lanes but consolidating all movements to a single signalized intersecting point would separate and streamline movements through the intersection. And since I-93 is on quite a sizeable viaduct here there's more than enough room to do this and it could be performed in conjunction with the inevitable replacement of the viaduct structure so that the current support structures underneath aren't in the way.
florida int streetview.jpg

With this configuration there would only need to be 3 signal phases (different colored arrows) and pedestrians could have either a full independent phase or have different segments on a walk whilst there is no traffic green to cross them. Modern adaptive signals could shorten or lengthen phases based on traffic volumes for each movement, prioritizing the yellow phases to keep the rotary from backing up too much from having a signal so close to its branch.

Florida intersection signalized.jpg
columbia 93.jpg

Apologies for the amount of white space couldn't crop it in paint and Windows has some weird browser software that was being a pain
 
another option to the Single Point Urban Interchange (shown above) is to do a diverting diamond interchange. its basically an SPUI but with the Columbia Rd approaches flipped so that all of the left turns (EB to NB on ramp, SB off ramp to EB, NB off ramp to WB, and WB to SB on ramp) dont have to cross traffic.
Of course, this being New England, peoples head would explode when they first saw it.
 
real_EthanHunt said:
another option to the Single Point Urban Interchange (shown above) is to do a diverting diamond interchange. its basically an SPUI but with the Columbia Rd approaches flipped so that all of the left turns (EB to NB on ramp, SB off ramp to EB, NB off ramp to WB, and WB to SB on ramp) dont have to cross traffic.
Of course, this being New England, peoples head would explode when they first saw it.
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One of the options presented in the, er, presentation is a diverging diamond under I-93. I'm a bigger fan of SPUIs for no particular reason; one of the problems with them is that the large paved area can make snow removal problematic, but presumably that's less of an issue under an overpass.
 
Scott said:
I am surprised because one important benefit of a rotary is that you never have cross over traffic to take a left where it may be dangerous
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The existing rotary isn't under the highway, it's 100ish' to the east. I have to loop all the way around it regularly, coming back from Franklin Park Zoo, and being able to just turn left onto I-93 would be awesome.
 
themissinglink said:
www.bostonglobe.com

Mass., Maine receive $11 million from wildlife crossing federal grants - The Boston Globe

Massachusetts and Maine have been selected as two of 16 states to receive a portion of $125 million in grants.
www.bostonglobe.com www.bostonglobe.com
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Oh, that's interesting, they're planning to replace the existing Appalachian Trail bridge over the Pike with a combined trail and wildlife crossing. That'll require some clever design. From the grant statement:
The project will offer separate and distinct areas for wildlife, pedestrians and hikers and include fencing to help funnel wildlife to the crossings
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I kind of doubt that they're going to design in separate trails for thru-hikers and regular pedestrians, but I suppose it's possible.
 
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ceo said:
Oh, that's interesting, they're planning to replace the existing Appalachian Trail bridge over the Pike with a combined trail and wildlife crossing. That'll require some clever design. From the grant statement:

I kind of doubt that they're going to design in separate trails for thru-hikers and regular pedestrians, but I suppose it's possible.
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I assume that's just bad phrasing (or language that sounds better for federal grant criteria/scoring or something).

There aren't any "normal" pedestrians, the south side of the bridge only goes to a hiking trail/undeveloped land, you can't walk anywhere else - so you're a hiker of some kind if you are using it.
 
ceo said:
The existing rotary isn't under the highway, it's 100ish' to the east. I have to loop all the way around it regularly, coming back from Franklin Park Zoo, and being able to just turn left onto I-93 would be awesome.
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I am from Dorchester, I know where it is, and it is not wrong to point out that part of the reason that a rotary was chosen way back when was to avoid having to take a left across traffic. Another reason was so that cars don't back up behind the car wanting to take a left. I was not objecting to potential changes, just surprised that a left turn would be added
 
Scott said:
I am from Dorchester, I know where it is, and it is not wrong to point out that part of the reason that a rotary was chosen way back when was to avoid having to take a left across traffic. Another reason was so that cars don't back up behind the car wanting to take a left. I was not objecting to potential changes, just surprised that a left turn would be added
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As of now, the circle gets completely backed up during rush hour from everyone trying to go around the circle from Morrissey to get on 93N. A more regimented left turn at a signalized intersection, plus the two lanes on Columbia dedicated to 93N (as shown in the documents) could solve this. I fear a new circle would run into the same issues that occur now. For higher capacity roads, sometimes a signaled intersection is superior to a roundabout.
 
A SPUI or DDI right next to a subway station seems idiotic, to me. Much of Dorchester is already cut off from its waterfront by the expressway, why would you want it to be even more of a barrier to get to the subway and the water?
 
as02143 said:
A SPUI or DDI right next to a subway station seems idiotic, to me. Much of Dorchester is already cut off from its waterfront by the expressway, why would you want it to be even more of a barrier to get to the subway and the water?
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I’m not sure what you think would be a better solution. Wouldn’t it be better to have signaled crosswalks at all of the ramps? A SPUI or DDI will include this and the current layout doesn’t have any (at the ramps or roundabout). Either proposed option would be a major improvement over the existing conditions
 
as02143 said:
A SPUI or DDI right next to a subway station seems idiotic, to me. Much of Dorchester is already cut off from its waterfront by the expressway, why would you want it to be even more of a barrier to get to the subway and the water?
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Would it be any worse than what exists now with having to cross slip lanes to enter a subway station? You wouldn't need a Florida sized SPUI because it wouldn't be interfacing with 8 Florida lanes of traffic but rather maintain the existing number of lanes and can eliminate the slip lanes. You're never gonna get a fantastic pedestrian experience with a highway exit and I don't see them removing it since this is America. A DDI is a different story that I think would be terrible for everyone involved.

Scott said:
I am from Dorchester, I know where it is, and it is not wrong to point out that part of the reason that a rotary was chosen way back when was to avoid having to take a left across traffic. Another reason was so that cars don't back up behind the car wanting to take a left. I was not objecting to potential changes, just surprised that a left turn would be added
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Problem is not only does all the traffic traveling on Columbia eastbound have to go around the rotary to get on 93N but also all traffic coming off 93N needs to go around the rotary to head westbound on Columbia. It's very unevenly loaded with demand to go all the way around rather than taking the 1st or 2nd exits meaning openings for other traffic to enter from other points are harder to come by. Reconfiguring the area so that the rotary doesn't have to handle 100% of 93N movements and Columbia westbound movements would allow those traveling elsewhere through the rotary an easier time and it to do its job better. The reason I propose an SPUI is because it has the least signal phases/traffic movements and smallest footprint for our purposes here. For the left turn backup concern: Because there are few phases they can individually be longer without too long of an overall cycle time, and the existing approach layout allows for a dedicated left turn lane all the way to Dot Ave whilst the left turn from the rotary onto 93S isn't nearly as high demand so the signal cycle could just be timed appropriately or have sensors.
 
Koopzilla24 said:
Would it be any worse than what exists now with having to cross slip lanes to enter a subway station?
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Yes, it would be worse. Longer crossings with exposure to wild highway drivers and then the interminable waits to cross. A DDI or SPUI would make this more like the Somerville highway of death for Dorchester.

It would be nice to make what doesn't work today better - get some better ped crossings here today over the exit and entrance ramps. Shortening the crossing distances, making them 90 degree turns. It's not rocket science.
 
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