Roundabouts vs Signals

[Mdcastle]

I've notice a lot of Mn/DOT projects have signals and roundabouts at seemingly random locations. Assuming you're building in a cornfield with plenty of land, what operational issues might lead you to pick one over the other, and is there any benefit to mixing them. The Flying Cloud Drive project has a roundabout, then a traffic signal, then another roundabout. Why not build three roundabouts?

[NE2]

If it's this project, it looks like Carver County made the decision.

[tradephoric]

Assuming you're building in a cornfield with plenty of land, what operational issues might lead you to pick one over the other

I don't like general rules, but...  if the AADT of an intersection exceeds 50,000, a roundabout probably isn't your best bet.  Unequal traffic distributions can also be problematic.

and is there any benefit to mixing them.

There could be a benefit as traffic signals help meter traffic.  Some signals operate solely for the purpose of creating gaps in traffic. 

[roadfro]

I've notice a lot of Mn/DOT projects have signals and roundabouts at seemingly random locations. Assuming you're building in a cornfield with plenty of land, what operational issues might lead you to pick one over the other, and is there any benefit to mixing them.

A couple of things. What's the traffic like? If it's not an overly-busy intersection, it might not meet traffic signal warrants but might be too busy for a 2-/4-way stop. There's also the operational costs...once you pave a roundabout there are no ongoing operational costs outside of pavement wear and occasional sign replacement; however, a traffic signal also has the electric cost of operating the signal, replacement bulb/hardware, and more potential for malfunction/maintenance needs.

and is there any benefit to mixing them.

There could be a benefit as traffic signals help meter traffic.  Some signals operate solely for the purpose of creating gaps in traffic.

You could also say that the roundabout also helps meter traffic in a way, as they could re-distribute a platoon into something more steady.

[txstateends]

Some places (I'm firmly convinced) only wanted to do a roundabout to install an ugly monstrosity like this:
https://www.google.com/maps?ll=32.961414,-96.825946&spn=0.001033,0.001853&t=h&z=19

instead of something on the order of, maybe a *fountain* or even nice landscaping.  Fortunately, over the years, the trees planted along the intersecting streets have grown enough to cover up most of the 'view' there, so I don't have to reach for the eye-wash as much now

[tradephoric]

You could also say that the roundabout also helps meter traffic in a way, as they could re-distribute a platoon into something more steady.

That's a good point.  I don't think i gave the best description when i stated that traffic signals help "meter" traffic.  I should have said traffic signals help create large gaps in traffic (making it easier for someone making a left out of a mid-block drive to find an available gap).