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Road Class ID

Use this dialog to specify parameters for road class according to Handbook N100. Roads are divided into different design classes, which set requirements for road widths, curvature, technical standards, cross-sections out to the shoulder, alignment parameters, intersection solutions and driveways, solutions for pedestrians and cyclists, public transport facilities, and lighting systems.

Where can I find the dialog?

In the toolbox, select the SFI Properties... icon, then the Properties tab, the Show button to the right of Road Class, and finally the Road Class ID tab.

Using the Dialog

The standard classes are installed with the program and cannot be changed by the user. For roads with other requirements, users can create their own design classes.

Handbook V120 explains and describes the parameters used when designing a road alignment, as well as the formulas they are part of. This formula set and the parameters are implemented in the Gemini Terrain road design library.

The parameters and other requirements are entered in this dialog, divided into the following tabs:

  • Road Class ID
  • Speed
  • Road and Lane
  • Superelevation
  • Stop
  • Intersection Solution (information only)

During construction, the design library continuously calculates values for the parameters, such as horizontal curve radius, vertical curve radius, clothoid, gradient, and so on. This is a useful tool that helps you design roads that meet the requirements of the standard.

See Handbook V120 Premises for Geometric Design of Roads for a detailed description of the formulas and basic parameters.

Some of the parameters are commented on below:

  • The option for Narrow road is an important parameter for roads with a single carriageway. If this is checked, the vehicle can use the entire carriageway in curves, resulting in smaller width expansions.
  • Vehicle type is used by the program to calculate width expansions in curves. You can define your own vehicles with the vehicle editor (Tools - Vehicle Editor).

A horizontal curvature (centerline) can contain three elements: straight line, circular curve, and clothoid:

Figure: A = Circle, B = Clothoid, C = Straight line

The option Requires clothoid in horizontal curvature determines whether the curves should be built with a clothoid or not: A–R–A or only R. If you check this option, the program will suggest values for A–R–A during construction. If you check fixed minimum radius, this becomes the standard value during construction.

A vertical curvature can contain three elements: straight line, circular curve, or parabola.

Figure: A = Crest, B = Sag

You can override the calculation of curve radii for horizontal and vertical curvature by entering fixed minimum values. This may be desirable for certain user-defined roads.