Alley widths, street frontages, were captured during the vector property effort and reside in their own feature class. 99% of the time, these features should be coincident with the square boundary. The exceptions to this are internal alley s that might be overlaid by a tax lot. They were captured largely to enable continuity within each square. Alley Polygon does not exist. They could be created with this data by using an automated routine which searches linear feature of the Record, Tax and Parcel Lots feature classes where Line_Classification = 3, 4 and 6, then turning these selected lines into poly s, another method would be clipping a square boundary with the tax and record lots.Created as part of the DC Geographic Information System (DC GIS) for the D.C. Office of the Chief Technology Officer (OCTO) and participating D.C. government agencies. Please visit http://vpm.dc.gov/ for additional information.