Tool to add triangular polygon

[AlanTonkin]

I have a road layout and at the road intersections I need to create what are termed "splays" in the Survey world. This is usually done by choosing the apex point and then creating a vertex a defined distance down each polygon edge running away from the apex point. The triangle is then created by joining the two new vertices with the apex vertex. I then need to merge this new triangular polygon with the adjoining polygon. See below:

And the end result being:

Is there a way to create a tool in ArcMap to achieve the above easily? Currently the method I am using is very cumbersome. Or has anyone already created such a tool?

Thanks in advance!

[BruceLang]

Reshape polygon seems appropriate.  See http://desktop.arcgis.com/en/arcmap/10.3/manage-data/editing-existing-features/reshaping-polygons.ht...

[AlanTonkin]

I know I can use the Reshape Polygon tool but I'm looking for something that will speed the process up significantly as I have a lot of these "chamfer" type triangles to add at these road intersections. In the interim I have decided to use a point layer as a construction layer and have used the "Point at end of line" construction tool to create the points at my specified distances down each polygon edge away from the apex point. I then just edit the vertices of the polygon to include my constructed points. I was ideally looking for a way that I could create a simple tool to automate my series of clicks and typing distances in.

[RebeccaStrauch__GISP]

I would say yes this is very doable (but can't help right now).  I would do a search on either "arcpy split along line"  or split line at point, or some of the other terms similar.  Questions that would help others...

• Do you already know the apex (i.e. maybe separate point layer)
• are the distances the same for 1) each apex, 2) each line/direction

You should look at Geometry—Help | ArcGIS for Desktop    You can do just about anything in a python script with this, that is breaking any feature down to it's smallest part, basically an x/y coordinate. But someone may have already written something to I would look around on the web.

The "official" code sharing page from esri now is here: ArcGIS Code Sharing