Unbuilt roads around metro Boston

[Charlie_mta]

One on 28 in Milton with a 45 MPH arrow straight approach is under design now.

On higher speed approaches, usually it's wise to put a small reverse curve in the approach road to slow down traffic before it enters the roundabout, such as this one:

 

[JeffDowntown]

On higher speed approaches, usually it's wise to put a small reverse curve in the approach road to slow down traffic before it enters the roundabout, such as this one:

The ones around Green Bay, Wisconsin look a lot like that.

There is one place near Green Bay where there are three of these in a row as part of the interchange of US 41 and WI 54. It is a bit much!

 

[Highwayguy]

On higher speed approaches, usually it's wise to put a small reverse curve in the approach road to slow down traffic before it enters the roundabout, such as this one:

Agreed. That is obviously the ideal, and what would happen on 88 if that intersection was to be replaced with a roundabout. S curves are standard treatment in DOT’s roundabout design guide for high speed roadways. I was referring to the roadway alignment for the mile or two prior to the intersection rather than the approaches themselves.

 

[jass]

Indeed. The state has been pretty keen on roundabouts and recently developed a white paper and design guide: https://www.mass.gov/lists/guidelines-for-the-planning-and-design-of-roundabouts

There's a lot of nuance with how they're designed, but in short if you think it's too much to ask people to slow down for a rotary then whoa boy. Let me tell you about what happens when people don't slow down/stop for a red light. Safety at intersections along high-speed roadways will always be difficult, but it's far preferable to have a few more drivers overrun curbs than to set up a situation where you'd expect high-speed T-bone crashes.

Not saying a roundabout is always the right solution, but a higher number of crashes isn't always a bad thing if crash severity is greatly reduced. Also, roundabout =/= rotary.

" Exit radius Multilane typically ranges between 200’ to 350 "
" However, if adequate deflection is achieved at the entry and maintained in the circulatory roadway, resulting in lower circulating speeds, the exit geometry can use flatter curves or tangents. "

Garbage. This is why American roundabouts are garbage. The lack of deflection on exit means cars are accelerating to 40mph as they arrive at the crosswalk.

Page 50 is a nightmare.

 

[ra84970]

I'm waiting for these roundabout innovations to make their way to Massachusetts highway building.

"Rotor" turbo roundabouts - with signalization, of course

I don't know if you all have experienced the types of multi-lane modern roundabouts that are partially "spiral" or "turbo" styled. This is where you have to select your lane before entering the circular roadway. MassDOT and DCR seem to be restriping a lot of the rotaries inside 128 with these principles, without rebuilding them. I think the most effective implementation that I've seen has been the "turbo" striping on the rotary at Exit 40 on Route 128. DCR has done some striping at the BU Bridge Rotary on Mem. Drive, kinda. And at the rotary on Alewife Brook Parkway at Concord Ave.

The next level of (no longer) circular intersections would be to go full-in on "rotor"-style turbo roundabouts with signalization like the example below.

Example from Westerlee, NL

This example is located at the end of the A20 freeway and is clearly meant to handle a lot of truck traffic given adjoining landuses. It was super wild to watch videos of this one --

 

[Equilibria]

I'm waiting for these roundabout innovations to make their way to Massachusetts highway building.

"Rotor" turbo roundabouts - with signalization, of course

I don't know if you all have experienced the types of multi-lane modern roundabouts that are partially "spiral" or "turbo" styled. This is where you have to select your lane before entering the circular roadway. MassDOT and DCR seem to be restriping a lot of the rotaries inside 128 with these principles, without rebuilding them. I think the most effective implementation that I've seen has been the "turbo" striping on the rotary at Exit 40 on Route 128. DCR has done some striping at the BU Bridge Rotary on Mem. Drive, kinda. And at the rotary on Alewife Brook Parkway at Concord Ave.

The next level of (no longer) circular intersections would be to go full-in on "rotor"-style turbo roundabouts with signalization like the example below.

Example from Westerlee, NL
View attachment 11762
This example is located at the end of the A20 freeway and is clearly meant to handle a lot of truck traffic given adjoining landuses.

Isn't this basically what Wellington "Circle" currently is? Also, this looks flat out awful for cyclists or pedestrians (I mean, that example doesn't even try). They'd be better off with grade separation.

 

[ra84970]

Isn't this basically what Wellington "Circle" currently is? Also, this looks flat out awful for cyclists or pedestrians (I mean, that example doesn't even try). They'd be better off with grade separation.

Wellington Circle is probably a bit too local access-y on the northern side of the intersection. This Dutch intersection design is highly limited in the access to the street/highway.

All of the Dutch intersections like this have cycling and walking handled either as under or overpasses. Note that the turbo roundabout referenced above even has a motorvehicle underpass to the left/west.

 

[FK4]

We need a rotary at Walter St @ Centre in W. Roxbury. That would do wonders in slowing down traffic, making that entire stretch less suicidal for pedestrians, and making turns there safer. The city doesn't want to do it and their overall inaction on the entire corridor is an embarassment. I'd rank Centre between the VFW and Arborway rotary as a top 3 disgrace as far as local Boston roads go, at least ones with very easily fixable issues.

 

[FK4]

I just came across this map on mapjunction that I thought I would share. I didn't know that that 1948 highway proposal that we transit history nerds often see on every metro site mentioned, actually had some detailed plans. Basically lays out a lot of stuff that was never built along with some stuff that was (McLellan, also the Rt 9 / Brookline Village widening that I never knew was part of a larger plan). At any rate I found it and find most interesting the Roslindale / Mattapan stuff that would have had an American Legion style highway running down through Rozzie and Hyde Park, toward Dedham. Links for specific maps on mapjunction dont work but it's the "1948 Massachusetts Highway Master Plan Detailed Mosaic". If you hover over where American Legion hits Cummins you will be able to find it as a choice in the maps. Very nice stuff.

As an aside for those truly nerdy, Mapjunction also is a great site to find the original paths of the Stony Brook and its tributaries, prior to their being put underground.