State Highways is used to display state highways on a map display. Each record represents a segment of highway where the county, route, postmile prefix, and postmile suffix are unchanging, and there are no gaps or overlaps in the postmiles.

Each segment is coded with the district, county, route, postmile prefix (if any), begin postmile, end postmile, and postmile suffix (if any). One additional field - AlignCode - should be understood by the user for effective use of this data set (refer to the Entity and Attribute Information section of this metadata).

The field AlignCode indicates if the state highway segment is on a Right alignment, Left alignment, Right side of an independent alignment, or Left side of an independent alignment. Where TSN (Transportation System Network - the source database) considers most state highways to have just a centerline, the underlying LRS (Linear Referencing System) linework that these segments are based upon has a line for each direction.

In some cases the right and left lines are identical (where there is no median). In other cases the right and left are separated (where there is a median, or dual carriageways), but TSN treats the segment as a single centerline. In the last case the underlying linework has dual carriageways, and TSN treats the segment as an independent alignment (where there are independent right and left alignments). In some cases (especially for small-scale mapping), it may be appropriate to display linework for just one alignment (e.g. Right alignment), and only for the other side where TSN indicates independent right and left alignments. In other cases (e.g. large-scale mapping), it may be appropriate to display linework for both alignments, regardless of how TSN treats the segment.

This is an example of a query string that displays linework only for the right alignment where TSN indicates just a centerline, and on both right and left alignments where TSN indicates independent alignments:

"AlignCode" <> 'Left'.

The bOdometer and eOdometer fields represent the actual distance in miles from the start of the highway to the begin and end of each highway section. This is in contrast to the begin and end postmile values, which no longer represent these values as each highway is realigned (and made longer or shorter) over time.