Assign Template Point Centerline

In roadway design situations involving varying pavement widths, Assign Template Point Centerline is an effective way to control the edge of pavement horizontal alignment as well as any other element in the template. This command assigns centerline (.CL) files to template ID points, independent of the main centerline, thereby controlling the horizontal location. The assignment of Template ID points to centerline files (.CL) is stored in Template Point Centerline files (.TPC). These files are then used by the Process Road Design and Road Network commands. The slope to these template points is based on the parameters defined in Design Template. Subgrades can be made to follow template IDs if their offset distances are defined not by distance but by reference to the template ID.

The commands that process Template Point Centerlines such as Road Network will make the template grades follow the template point centerlines including along their curves for the output of the template 3D polylines and road TIN surface. This way Template Point Centerlines can be used to create rounded medians and edge-of-pavements that follow alignments that are independent of the main centerline as shown here.
There are a few key settings to a road design with medians as shown here.

• Use Template Point Centerlines to control the alignments of the median and curbs. The Adjust Next Outside Grade Distance option should be ON.
• In the Design Template command, for a template (TPL) with a median crossing the centerline, use the Profile Delta Z set to the height of the median.
• Use the Template Series File command to define the sequence and station ranges of templates (TPL) switching between templates with and without medians. Turn OFF the option to Transition With Previous Template In Series.

Prompts

First you are prompted to create a new Template Point Centerline file (.TPC) or edit an existing one. 

Next the Define Template Alignments dialog is presented, showing a list of existing Template ID-Centerline assignments. Use the Add, Edit and Delete buttons to manage the list of template point centerlines. The Report function creates a report of the template point centerlines in the standard report viewer. The Reference Template is optional for setting the road template (TPL) to use for selecting the template point description from a lookup list.

The Add and Edit buttons bring up the Template Point Centerline Settings dialog.  First, set the Template Point Description which refers to the Template ID for an element in the Template (TPL) defined by the Design Template command. Next, pick the Specify Centerline File button, to choose the file (.CL) to assign to the Template Point ID. Alternatively, you can use the Screen Pick button to select a polyline from the drawing that the program will use to generate a centerline. Specify if this assignment is for the Left or Right side of the main centerline.

The Adjust Next Outside Grade Distance controls how template elements are affected that are outside from the current Template Point Description. This option controls whether to hold the grade distance or grade offset from the main centerline for the outside template elements. When this option is on, the outside grade distances are adjusted by the same amount that the template point centerline adjusts the horizontal alignment. When this option is off, the outside grade distances remain set by their distance defined in the template. For example, consider a template that has an inside median grade (MED) followed by an edge-of-pavement (EP) and the MED has a template point centerline. When this option is on and the template point centerline shifts the MED out 2 feet, then the EP grade is reduced by 2 feet so that the EP offset from the main centerline isn't affected. When this option is off and the MED is shifted out 2 feet, then EP grade distance doesn't change and the EP offset from the main centerline is shifted out 2 feet.

The Skip Grade When Centerline Missing means that the template will only contain the element at stations that have a template point centerline for it. The Additional Grades To Skip specifies other related template elements to skip in this case. The option applies to template elements like intermittent medians that you only want included in the template for stations where they have a template point centerline defined.
Here are two sections along the roadway, illustrating the varying lane widths on the right side of the main centerline. These sections are created by Process Road Design with the TPC set in the input files and these sections are viewed with the Input-Edit Section File command.