Parcels and R.O.W. Lines that Adjust to the Road Centerline

In past versions of Civil 3D, right-of-way (ROW) lines could easily be created from the centerline of a road.  Then, parcels could be built off of the frontage created by these ROW lines.  The problem was that if the centerline of the road shifted, the ROW lines and the parcels would not adjust to the new alignment.  It was then up to the designer to manually shift all the parts dependant on the centerline.

New in Civil 3D 2010 is the ability to create offset alignments that stay a uniform distance away from the centerline.  When the centerline changes, those changes are reflected through to the offset alignments.  The parcels created on the frontage of this ROW change as well.  Here is a very basic example of the power of offset alignments. 

The following image shows a parcel with a Polyline running through it. 

The Polyline will be turned into an alignment using the Create Alignment from Objects command.  We will make sure to include this new alignment in the Site in which the parcel resides thereby creating a subdivision and two parcels where one existed.  Also, we will specify the type of alignment as Centerline, a new feature in Civil 3D 2010. 

Next, we will create the ROW alignments using the Create Offset Alignments command.  The program will ask the user to specify the alignment from which the offsets will be created and then a dialog box will open. 

In this box, we will specify a 25 offset from centerline, adjust the styles and names and hit the OK button.  We now have four parcels, two contained within the ROW and two outside the ROW ready for subdivision.

We can now make adjustments to the centerline alignment and watch as the offset alignments follow it.  To show an even more powerful capability, we will create some parcels and allow them to be adjusted with the alignments.

To quickly and easily create an array of parcels, we will use the Parcel Creation Tools command to launch a toolbar.  We will use the Slide Line Create option.

We will choose the parcel on the north side of the road to subdivide first making sure we set our minimum lot size, frontage options, automatic mode to On with the remainder redistributed, choose the starting and ending point along the frontage, and finally choose the angle from the ROW at which our lot lines will be drawn.  This will create equal sized parcels that obey the settings established in the dialog box.  We will then do the same for the parcel on the south and check out our handiwork.

Now we can make any adjustment to our initial centerline alignment and watch as the parcels and ROW lines follow the adjustments.

The user must keep in mind that the parcels may shift slightly away from the original design intent but lot lines created by Slide Line are easily adjusted back to a suitable location.

In general, it is recommended that road alignments be mostly set by the time parcel creation occurs.  But, if minor adjustments like the radius of a subdivision roadway curve need to be made, then this tool will save the user from having to completely break down and build back up an entire block of parcels.