Symbolizing individual highway network segments in ArcMap

Question

I have a highway layer that I need to style in ArcMap in such a way to differentiate between individual highway sections, ideally using no more than 6-7 distinct colors. Each highway is divided into one or more sections. Highways have Road Number and Section Number attributes that I can use for styling. The symbology will need to be exportable to ArcPad. I can calculate/add new fields to the table, if that helps.

Here's an image of how a section of highway may look like:

Note that in the image, the colors aren't repeated, but they will definitely have to be over the entire highway network. All I'm looking to accomplish is show highway section breaks with a limited subset of colors.

Answer 1

In ArcMap go to the menu Customize -> Style Manager.

In your personal style (or whatever works for you) click on Color Ramps. In the area to the right, right-click New -> Preset Color Ramp...

Change the colors to what you want. If you only want 6 or 7 colors you'll have to repeat colors.

Use this ramp to symbolize the highway segments.

This will get you the same effect if in a hackish kind of way.

Answer 2

I hacked together a quick script yesterday to add a category to each highway section based on the sections it intersects. The script will automatically decide what the max number of categories is as it goes along. Its not necessarily the most efficient/clean method, but I didn't any more free time to look into it. I'm also fairly new at python/arcpy, so the code could use a bit of cleanup:

import arcpy
from arcpy import env

# Set the workspace
env.workspace = "C:/Projects/Misc/HighwaySymbology"

# Create a copy of the highways shapefile
arcpy.CopyFeatures_management("highways.shp", "highways_out.shp")

# Add a category field
arcpy.AddField_management("highways_out.shp", "hwycat", "LONG", 9)

# Create a feature layer
fl = arcpy.MakeFeatureLayer_management("highways_out.shp", "Highways")

# Create the update cursor
rows = arcpy.UpdateCursor("highways_out.shp")

# Create the in-memory layer to select with
arcpy.MakeFeatureLayer_management("highways_out.shp", "HwySelection")

# Loop through every highway segment, one by one
for row in rows:
    arcpy.SelectLayerByAttribute_management("HwySelection", "NEW_SELECTION", "FID = " + str(row.FID))

    arcpy.SelectLayerByLocation_management("Highways", "INTERSECT", "HwySelection", "", "NEW_SELECTION")
    numSelHwys = int(arcpy.GetCount_management("Highways").getOutput(0))

    # Number of selected highways should always be > 1, 
    # as it will at least select the current highway
    if numSelHwys > 1:
        # Loop through all sections of the road and find the
        # lowest unused highway category
        selHwys = arcpy.SearchCursor("Highways")

        hwyCategories = []
        for selHwyRow in selHwys:
            # Skip the current highway
            if selHwyRow.FID == row.FID:
                continue

            if selHwyRow.hwycat > 0:
                hwyCategories.append(selHwyRow.hwycat)

        # Sort the list and find the first available category
        hwyCategories.sort()
        lastCat = 0
        for cat in hwyCategories[:]:
            if cat - lastCat > 1:
                break
            else:
                lastCat = cat

        lastCat += 1
        row.hwycat = lastCat
        rows.updateRow(row)

    else:
        # No adjoining segments, set the category to 1
        row.hwycat = 1
        rows.updateRow(row)


print
print "DONE"