Inconsistency defining stationing (Pset_Stationing) and superelevations (Pset_Superelevation) for roadways

To define a station along an alignment an IfcRelNests relates an IfcReferent to an IfcAlignment. The IfcReferent is located with an IfcLinearPlacement defined along the IfcAlignment. A station is defined with IfcPropertySet containing Pset_Stationing data and is related to the IfcReferent with IfcRelDefinesByProperties.

IfcAnnotation is used to define a superelevation transition along a highway alignment. The IfcAnnotation is placed using IfcLinearPlacement defined along the IfcAlignment, just as the IfcReferent except that IfcRelNests doesn't seem to be applicable for IfcAnnotation. The IfcAnnotation.PredefinedType is set to .SUPERELEVATIONEVENT. For each element of the superelevation transition (start entry transition, end entry transition, begin full super, end full super, start exit transition, and end exit transition) a IfcRelDefinesByProperties relates each IfcAnnotation to a IfcPropertySet containing Pset_Superelevation data.

Why the inconsistency? It seems like Pset_Superelevation data is equally well related to an IfcReferent.

The documentation for IfcReferent [5.4.3.41](https://standards.buildingsmart.org/IFC/DEV/IFC4_3/RC4-voting/HTML/link/ifcreferent.htm) says "Referents may be used for several scenarios: indicating transitions of cross-sections (e.g. beginning of curvature where road is relatively flat, maximum curvature having super-elevated cross-slope to accommodate design speed). However, [5.4.2.18](https://standards.buildingsmart.org/IFC/DEV/IFC4_3/RC4-voting/HTML/link/ifcreferenttypeenum.htm) IfcReferentTypeEnum does have have a value to indicate the referent is defining any portion of a superelevation transition. It seems like the intent is to relate Pset_Superelevation with IfcReferent but the specification doesn't provide details on how this is to be accomplished.

Additionally, [5.4.3.6.3](https://standards.buildingsmart.org/IFC/DEV/IFC4_3/RC4-voting/HTML/link/ifcannotation.htm) indicates that the property sets for objects that are applicable to IfcAnnotation are Pset_AnnotationCounturLine, Pset_AnnotationLineOfSight, Pset_AnnotationSurveyArea, and Pset_SoundAttenuation. However. [5.4.2.2](https://standards.buildingsmart.org/IFC/DEV/IFC4_3/RC4-voting/HTML/link/ifcannotationtypeenum.htm) IfcAnnotationTypeEnum has a SUPERELEVATIONEVENT value and [7.9.4.19](https://standards.buildingsmart.org/IFC/DEV/IFC4_3/RC4-voting/HTML/link/pset_superelevation.htm) says Pset_Superelevation specifies the general properties for a Superelevation event for IfcAnnotation. This is contradictory information. The specifications seem to say that Pset_Superelevation both is and is not applicable to IfcAnnotation - which is it?.

Some additional comments on Pset_Superelevation documentation:

[7.9.4.19](https://standards.buildingsmart.org/IFC/DEV/IFC4_3/RC4-voting/HTML/link/pset_superelevation.htm) Pset_Superelevation, Side property refers to the measurement of a width. What width is being referred to? The PEnum_SideType has values LEFT, RIGHT, BOTH. What demarcates LEFT from RIGHT?

[7.9.4.19](https://standards.buildingsmart.org/IFC/DEV/IFC4_3/RC4-voting/HTML/link/pset_superelevation.htm) Pset_Superelevation, Superelevation property is not specific with respect to the sign convention for the ratio measure(slope). Is a positive value slope upwards, left to right? Are positive values favorable slopes and negative values adverse slopes in terms of the righting or overturning effects of centrifugal forces?

[7.9.4.19](https://standards.buildingsmart.org/IFC/DEV/IFC4_3/RC4-voting/HTML/link/pset_superelevation.htm) Pset_Superelevation, TransitionSuperelevation property only defines a LINEAR transition. Partial parabolic and full parabolic transitions are also common.

[7.9.4.19](https://standards.buildingsmart.org/IFC/DEV/IFC4_3/RC4-voting/HTML/link/pset_superelevation.htm) Pset_Superelevation does not provide a way to specify where the transition pivot point is located. The image below shows pivot occuring about the inside edge, centerline, or outside edge of pavement.