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.