I inherited layers that divided each county into "Routes". The previous work had no precision and the routes had gaps and overlaps. I tried several different techniques and found the following to be most expeditious and precise. I used the Align Tool, but it removed some curves and precise angles that I had put much time into creating.
Assuming the drawing shows a Northern Polygon and a Southern Polygon being separated by a Road.
- Select a separation line. If the map is cluttered or the cut is complex, create a new layer for the cutlines by tracing the Streets Layer or by using a definition query on the Streets Layer to only show the needed roads.
- Redraw the Northern polygon so that it completely overlaps the road. Do the same with the Southern polygon.
- Select both Polygons and use the Cut Polygons Tool to trace along the road. This will slice both polygons along the same road, using the same vertices, and create two new "waste" polygons.
- Delete the newly created polygons.
Note: for further precision, divided highways and interstates can be used by selecting the North/South or East/West line or create a copy then use Collapse Dual Lines To Centerline Tool to create a single line down the middle for splitting polygons.