TubeCAD allows multiple tubes to be drawn and projected together within a TubeCAD layout. This feature aids in finding the distance and anglular relationship between tubes where they meet in assemblies. (This image is from an AutoCAD drawing created by TubeCAD.)

The images below show a multi-tube assembly rendered in IntelliCAD 98.
(IntelliCAD is currently bundled with every TubeCAD 5.8 package.)

Click on the images to see enlarged views.