AutoCAD P&ID is the best program on the market for creating and documenting your 2D and 3D piping and instrumentation designs. Autodesk AutoCAD P&ID 2016 is more object-oriented compared to standard AutoCAD, so you get a smarter program while still working in the familiar AutoCAD environment. 

AutoCAD P&ID allows you to produce your instrumentation and process diagrams more quickly, easily and efficiently. 

As of April 2017 AutoCAD P&ID ceased to be a separate title. However, the AutoCAD P&ID functionality is still available in AutoCAD 2019 and in Architecture, Engineering & Construction Collection 2019.

This is the only way, in the new licensing structure, to "buy" AutoCAD P&ID 2016 (further information on licensing).