ScottRAB

   All modern roundabouts have median islands separating incoming and outgoing auto traffic.  Pedestrians don't have to find a gap in two directions of traffic, just one.  This is safer for pedestrians, especially for younger or older ones, because they only have to concentrate on one direction of traffic at a time.  This is what is meant by two-phase. Cross the first half, pause if you need to, then cross the second half.  On multi-lane crossings pedestrian beacons or signals are often added if the auto (or pedestrian) traffic is too numerous.  The signals can also be two phase, requiring the pedestrian to push a second button when they get to the median.  The median can also have a Z path to reorient the pedestrian to view oncoming traffic.  Also, the signals usually rest in off, so they are only activated if a pedestrian needs the help crossing. This way only motorists that need to stop are delayed.

     Modern roundabouts are the safest form of intersection in the world (much more so than comparable signals).  Visit http://tinyurl.com/iihsRAB for modern roundabout FAQs and safety facts.  Modern roundabouts, and the pedestrian refuge islands approaching them, are two of nine proven safety measures identified by the FHWA, http://tinyurl.com/7qvsaem
   The FHWA has a video about modern roundabouts on Youtube, or check out the IIHS video (iihs dot org).  

First cost is the wrong way to compare projects. It would be like buying a car without knowing the fuel economy or safety of the thing, just its price to buy. Present Value Life Cycle Cost Analysis (LCCA) is the best way to compare two or more choices. When comparing modern roundabouts to signals for a 20-year life cycle (the standard period), modern roundabouts usually cost less. Costs to compare include: first cost (design/land/construction), operation and maintenance (electricity, re-striping, upgrades, etc.), crash reduction (what’s your/your family’s safety worth?), daily delay (what’s your time worth?), daily fuel consumption (spend much on gas?), point source pollution (generated by stopped vehicles = health cost), area insurance rates (this costs more where it is less safe to drive). Each of these things, and others, can be estimated for any two choices and everyone near or using the project area will pay some portion of all of these costs.