- Jul 15, 2006
- Reaction score
The ones around Green Bay, Wisconsin look a lot like that.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.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:
" Exit radius Multilane typically ranges between 200’ to 350 "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.
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.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.
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.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.