Methuen Rotary interchange reconstruction begins

[roadman]

Among other things, this means that peak hour breakdown lane use on I-93 will be eliminated between the north end of the Merrimack River bridge and the Pelham Street interchange.  This change, which starts next Monday (July 28th), is to accommodate the temporary lane configurations within the project area.

http://blog.mass.gov/transportation/massdot-highway/methuen-rotary-project-travel-impacts/

[DJStephens]

Interesting.  The link shows a rotary being replaced by a partial cloverleaf.   Up there they are working to get rid of rotaries, down here, they think they are the next great thing. 

[froggie]

Up there they are working to get rid of rotaries, down here, they think they are the next great thing.

You're not confusing rotaries with roundabouts, are you?

[DJStephens]

am lumping them all together in the same bucket.  doesn't a "roundabout" really a small rotary, anyway??    Mentioning that they were getting rid of rotaries was  meaning MassDPW, had removed such facilities as the former Alewife, Bourne, and Sagamore rotaries.   And there probably are more.  Wonder if that "Reformatory Circle" near a state pen on their state route 2 still exists.  Remember it as being pretty ugly, and dated.   

[Alps]

am lumping them all together in the same bucket.  doesn't a "roundabout" really a small rotary, anyway?? 

No. A roundabout has all entering legs yield to traffic inside.

[Pete from Boston]

am lumping them all together in the same bucket.  doesn't a "roundabout" really a small rotary, anyway??    Mentioning that they were getting rid of rotaries was  meaning MassDPW, had removed such facilities as the former Alewife, Bourne, and Sagamore rotaries.   And there probably are more.  Wonder if that "Reformatory Circle" near a state pen on their state route 2 still exists.  Remember it as being pretty ugly, and dated.

It's still there.  It's hardly the biggest problem on Route 2 in that area, which is a distinction reserved for the traffic-light intersections.  At least Crosby's Corner is moving along.  I had some pics of that work I long ago forgot to post, but I never thought I'd see it even start.

[mass_citizen]

am lumping them all together in the same bucket.  doesn't a "roundabout" really a small rotary, anyway?? 

No. A roundabout has all entering legs yield to traffic inside.

In MA, this is also the law in regards to rotaries. The issue with this particular interchange is that because people exiting the highway had to yield to traffic inside the rotary, traffic would frequently backup onto the mainline highway at rush hour.

[mass_citizen]

am lumping them all together in the same bucket.  doesn't a "roundabout" really a small rotary, anyway??    Mentioning that they were getting rid of rotaries was  meaning MassDPW, had removed such facilities as the former Alewife, Bourne, and Sagamore rotaries.   And there probably are more.  Wonder if that "Reformatory Circle" near a state pen on their state route 2 still exists.  Remember it as being pretty ugly, and dated.

IIRC, there is still a rotary on the Cape side of the Bourne bridge. In the example of the Sagamore and the Methuen rotary eliminations, they were/are being replaced with facilities that are more efficient than a rotary or roundabout. In Sagamore, a complete flyover was built allowing uninterrupted flow over the bridge. In Methuen a complete interchange should also be more efficient. 

In my experience of growing up with MA rotaries as well as driving through some of the newer roundabouts, I do find that the larger diameter rotaries allow more sight distance for yielding when entering. I also believe that the higher speeds in rotaries allow for wider gaps between cars allowing for easier entry. This combined with the fact that the roadway within a rotary is typically wider than a roundabout (usually rotaries are about 2-3 lane widths), cars can often use that space as an acceleration/deceleration lane. IMO, replacing a rotary with a flyover/interchange is a good idea. Replacing it with a traffic light or smaller roundabout not so much. I do like roundabouts though and I believe they are much better than signalized intersections. However I don't know of any examples in this area of a roundabout replacing a rotary. Usually it becomes a signalized rotary as in Chelmsford MA 4 @ US 3, or it becomes an interchange/flyover. I believe there are plans to eventually replace the Concord rotary with a flyover.

[Alps]

am lumping them all together in the same bucket.  doesn't a "roundabout" really a small rotary, anyway?? 

No. A roundabout has all entering legs yield to traffic inside.

In MA, this is also the law in regards to rotaries. The issue with this particular interchange is that because people exiting the highway had to yield to traffic inside the rotary, traffic would frequently backup onto the mainline highway at rush hour.

Your next post reminded me another difference - roundabouts generally have a certain maximum diameter that's related to their operation. Rotaries are much larger - as much as half a mile.

[froggie]

I also believe that the higher speeds in rotaries allow for wider gaps between cars allowing for easier entry. This combined with the fact that the roadway within a rotary is typically wider than a roundabout (usually rotaries are about 2-3 lane widths), cars can often use that space as an acceleration/deceleration lane.

The downside to this is that vehicle speeds are higher in the rotaries, and operational experience suggests that the higher speeds make them less safe than roundabouts.

I've also found it easier to enter roundabouts than rotaries in part because of the slower speeds.  Don't need as much room to merge in at 10 MPH than you do when rotary traffic is going 30.