Roadway Standards - Configure - Concepts

AGi32 provides several roadway standards to chose from when specifying a roadway calculation grid. However, the user may also define a "custom" standard by clicking the Configure button in the Calculation Points - Road dialog. This opens the Roadway Standards dialog. You may start with any of the existing standards, modify point spacing, observer location, and other characteristics, as well as the metrics to include in the custom standard. This new standard is then saved for future reference and use.

The calculation zone may cover one direction of traffic or two-way traffic. For two-way traffic, AGi32 assumes no median width. You may also change the side of the road that the driver is on.

The default settings in the Roadway Standards dialog are determined by the Roadway Standard that is showing in that field (top of dialog). The Calculation Metrics defined by the selected standard are listed in the field on the left side of the dialog. The Configure button below this list allows you to select the metrics to include in the custom standard. Definitions of the roadway metrics may be found in Calculation Metrics.

Clicking on one of the metrics listed on the left gives it focus, and the default definitions of the Calculation Grid point spacing and the Observer position are displayed.

The point spacing across and along the road are defined separately. (Calculation tab)

• For across-road spacing, you may specify:
  • a set spacing,
  • a fixed number of rows of points per lane or per roadway (carriageway), or
  • point spacing based on location of the first point, the number of rows of points desired, and their maximum spacing.
• For along-road spacing, you may specify:
  • a set spacing, or
  • the number of columns of points within a luminaire cycle.

On the Observer tab, you may specify one Observer location per row of points, one per lane, or one for the entire roadway. In addition, you may also specify the height of the Observer above the roadway surface and the distance of the Observer from the beginning of the grid or from each calculation point. In some of the standards,depending on the metric, the Observer's location may be based on a Mounting Height Equation. The default values of this equation may be changed.

It is important to note that the R-Tables are based on empirical data for an observer with a viewing angle of 1 degree below horizontal. If the Observer's height or distance from the grid points changes, this will affect the viewing angle. Small changes will have small effects, but larger changes could invalidate the calculation.

For additional information on creating a custom standard, click on the Procedures tab at the top of this topic.