Peter Dobratz (2018-07-11 07:05:45+00:00): Note: I've reverted this changeset fully in:
https://www.openstreetmap.org/changeset/60597789

First of all, this section of road is not a dual-carriageway.  There is no physical separation between the forward and backward direction.  I'm not sure how you came to the conclusion to make this a dual-carriageway.

However, if this were correct to separate this into a dual-carriageway, then this changeset still would have had problems:

Transit Route Relations:
There were errors in the relations for bus route 4.  If you are not familiar with transit route relations, these are setup so that there is a separate relation for each route variation.  Most bus routes have at least 2 route relations (one for each direction of the route).  The ordering of the members in the relation is significant (Nodes for bus stops, followed by Ways for the route to be followed in order).  After your edit, the Ways for the route were not in the correct order.  The editor iD does not fully support relation editing.  Specifically, iD does not allow you to re-order the members of the relation to be in the correct order.  If you are editing route relations, please use JOSM as if you can download the whole route relation and verify that the members are in the correct order.  JOSM will also warn you if you try to upload a transit route relation that contains a gap.

Admin boundaries:
In this area, we have setup admin_level=10 admin boundary relations for neighborhoods.  In some cases, the roads themselves are used in the admin boundary relation.  However, if there is a dual-carriageway, then the roads are not used in the admin boundary, but instead a separate Way is drawn in between the road Ways.  This separate Way for the admin boundary does not have tags as the tags are already on the relation.  In your edit you have both sides of the dual-carriageway as part of the admin boundary, creating a gap in the admin boundary relation.  Again, please use JOSM for tasks like this as it lets you download the entire admin boundary and verify that there are no gaps.

Sidewalks:
Sidewalks are tagged as attributes of the road, with one of:
sidewalk=no
sidewalk=left
sidewalk=right
sidewalk=both
For a single carriageway with sidewalk=both, this indicates that there are sidewalks on both sides of the road.  When creating a dual-carriageway, this usually changes to sidewalk=right to indicate that there is a sidewalk along the right side of the dual-carriageway (and no sidewalk in the area between the dual-carriageway).  Also, to indicate that pedestrians can cross the dual carriageway at a crosswalk, mark the ends of the crosswalk Nodes using highway=crossing and draw a Way connecting them with highway=footway and footway=crossing.

Bicycle Lanes:
For bicycle lanes, the tags may also need to be altered when converting from a single to dual carriageway.  In this case, it was correct to leave it as cycleway=lane, but on a single carriageway there may be tags like cycleway:left=lane or cycleway:right=lane.  These is a slightly more elaborate tagging scheme from sidewalks.

Turn restrictions:
In this case, there is a turn restriction only_straight_on indicating that you cannot make a left turn from Southeast Division Street heading east to the northbound onramp onto I-205.  When splitting this into a dual carriageway, you have retained this turn restriction, but it should have been deleted.  Care needs to be taken that the members of the turn restriction are correctly assigned roles "from", "via", and "to".  If there was a traffic island separating the road directions on Southeast Division Street, then you would not be able to make a turn across the median traffic island.  In general, turn restrictions should not be used when the road geometry and the oneway tags already imply the turn restrictions.  Typically, at the start and end of a transition from single to dual carriageway, there is either an only_straight_on turn restriction of a no_u_turn turn restriction to indicate that you have to continue on the road and are not allowed to turn around after the traffic island ends.  Note that local laws dictate that you are not allowed to make a U-turn unless there is a sign specifically allowing it.  Check out the Bing streetside images here for additional verification.

Lanes:
This area has detailed lane tagging, including tags lanes, lanes:forward, lanes:backward, turn:lanes, turn:lanes:forward, turn:lanes:backward.  Typically, when converting from a single to dual carriageway the lanes:forward and lanes:backward tags are removed and the lanes tag takes on the respective values.  In this changeset, you have not paid attention to these tags and you have this showing as 4 lanes in one direction and 5 lanes in another direction.  For editing turn:lanes, I use the JOSM plugin turnlanes-tagging (I believe developed by MapBox).  See this informative blog post:
https://www.mapbox.com/mapping/mapping-for-navigation/adding-turn-lanes/



If you can elaborate on the rationale for making this section of Southeast Division Street a dual-carriageway, then I can assist you in making these types of edits correctly.  Again, I recommend JOSM as it has a warning system built-in that would alert you to a lot of these problems.