Exchange Requirement: Vertical Alignment
Name
Vertical Alignment
Identifier
er_vertical-alignment
Change Log
| Date (yyyy-mm-dd) | Action | Author (email) |
|---|---|---|
| 2025-12-09 | Initial draft | AI Generated |
Project Stage
Select the applicable project stage(s); remove rows that do not apply.
| Code | Stage |
|---|---|
| 0 | Portfolio requirements |
| 1 | Conception of need |
| 2 | Outline feasibility |
| 3 | Substantive feasibility |
| 4 | Outline conceptual design |
| 5 | Full conceptual design |
| 6 | Coordinated design and procurement |
| 7 | Production information |
| 8 | Construction |
| 9 | Operation and maintenance |
| 10 | Disposal |
Overview
Provide a textual overview of the exchange requirement under the headings Scope, General Description and Information Description. Keep it non-technical and aimed at an executive audience.
Scope
The scope of this exchange requirement is to enable the exchange of vertical alignment geometry including grades, vertical curves, profile references, and elevation data necessary for roadway profile design and earthwork calculations.
General Description
Vertical alignments define the profile view geometry of roadways, establishing the finished grade elevations along the alignment. This exchange requirement captures grade slopes (tangents), vertical curves (crest and sag), and the relationship to reference surfaces. The information model supports multiple vertical alignments per horizontal alignment (for superelevated sections) and enables coordination between roadway profiles and drainage design.
Information Description
The information exchanged through this requirement includes the following parts:
- Alignment General
- Vertical Alignment Reference
- Vertical Alignment Offsets
- Sight Distance
- Vertical Alignment Grades
- Vertical Curve Type
- Vertical Curve Lengths
- Vertical Alignment Key Stations and Elevations
Information Requirements
Preconditions
Before exchanging vertical alignment information, the following information must be available: Horizontal alignment must be established (see Exchange Requirement: Horizontal Alignment). Existing ground surface or digital terrain model must be available. Design criteria including maximum grade and minimum curve length standards must be established. Vertical control survey data and benchmark references must be defined.
Parts
A part is a set of information that achieves a specific purpose or function within this exchange requirement (for example: Select Object, Assign To Group, Associate Library Reference). An exchange requirement is expected to consist of many parts.
Repeat the following block for each part.
Part: Alignment General
- Purpose: Provide general alignment identification, description, and classification data for project organization and document management.
Concept: Alignment Classification and Identification
- Purpose: Establish basic identification and classification of the vertical alignment for design coordination.
Provide a table with the set of information requirements for each concept. Extend the table as needed.
| Idea | Explanation |
|---|---|
| Alignment ID | Unique identification of the alignment for reference for vertical alignment, corridor elements, and other roadside components. (Type: STRING, Cardinality: R) |
| Alignment Description | Description of the alignment to further explain purpose and/or location. (Type: STRING, Cardinality: R) |
Part: Vertical Alignment Reference
- Purpose: Define the relationship between the vertical alignment and reference surfaces or datums for elevation control and survey coordination.
Concept: Vertical Datum Reference
- Purpose: Establish elevation datum and reference surface relationships for survey control and design coordination.
Provide a table with the set of information requirements for each concept. Extend the table as needed.
| Idea | Explanation |
|---|---|
| Horizontal Alignment ID | The horizontal alignment to which the vertical alignment is associated. (Type: STRING, Cardinality: R) |
Part: Vertical Alignment Offsets
- Purpose: Describe the purpose of the Vertical Alignment Offsets part
Concept: Vertical Alignment Offsets Information
- Purpose: Describe the purpose of capturing Vertical Alignment Offsets information
Provide a table with the set of information requirements for each concept. Extend the table as needed.
| Idea | Explanation |
|---|---|
| Offset from Horizontal Alignment | The distance measured from a primary alignment (centerline of the road) to another point of interest, such as a secondary road, lane, or feature like a shoulder or barrier. (Type: REAL, Units: Feet, Cardinality: O) |
Part: Sight Distance
- Purpose: Describe the purpose of the Sight Distance part
Concept: Sight Distance Information
- Purpose: Describe the purpose of capturing Sight Distance information
Provide a table with the set of information requirements for each concept. Extend the table as needed.
| Idea | Explanation |
|---|---|
| Headlight sight distance | Stopping sight distance for a sag vertical curve (Type: REAL, Units: Feet, Cardinality: O) |
| Stopping sight distance | Stopping sight distance is the distance necessary for a vehicle traveling at or near the design speed to stop before reaching a stationary object in its path. For vertical alignments, applies to crest vertical curve. (Type: REAL, Units: Feet, Cardinality: O) |
| Passing sight distance | On two-lane, two-way roadways, provision for a vehicle to pass a slower vehicle while occupying the lane regularly used by opposing traffic. (Type: REAL, Units: Feet, Cardinality: O) |
| K Value | The horizontal distance needed to produce a 1% change in gradient. (Type: REAL, Units: Feet, Cardinality: O) |
Part: Vertical Alignment Grades
- Purpose: Describe the purpose of the Vertical Alignment Grades part
Concept: Vertical Alignment Grades Information
- Purpose: Describe the purpose of capturing Vertical Alignment Grades information
Provide a table with the set of information requirements for each concept. Extend the table as needed.
| Idea | Explanation |
|---|---|
| Incoming Grade | Slope of profile as it approaches a specific point. Typically expressed as a percentage, indicating the vertical rise or fall over a horizontal distance (Type: REAL, Cardinality: R) |
| Outgoing Grade | Slope of profile as it departs a specific point. Typically expressed as a percentage, indicating the vertical rise or fall over a horizontal distance (Type: REAL, Cardinality: R) |
| Incoming Grade | Slope of profile as it approaches a specific point. Typically expressed as a percentage, indicating the vertical rise or fall over a horizontal distance (Type: REAL, Cardinality: R) |
| Outgoing Grade | Slope of profile as it departs a specific point. Typically expressed as a percentage, indicating the vertical rise or fall over a horizontal distance (Type: REAL, Cardinality: R) |
Part: Vertical Curve Type
- Purpose: Describe the purpose of the Vertical Curve Type part
Concept: Vertical Curve Type Information
- Purpose: Describe the purpose of capturing Vertical Curve Type information
Provide a table with the set of information requirements for each concept. Extend the table as needed.
| Idea | Explanation |
|---|---|
| Symmetrical Curve | A vertical curve in which the Point of Vertical Intersection (PVI) is located at the midpoint between the Point of Vertical Curvature (PVC) and the Point of Vertical Tangency (PVT). This configuration results in equal curve lengths on both sides of the VPI, providing a balanced transition between grades. (Type: BOOLEAN, Cardinality: R) |
| Unsymmetrical Curve | A vertical curve in which the Point of Vertical Intersection (PVI) is not located at the midpoint between the Point of Vertical Curvature (PVC) and the Point of Vertical Tangency (PVT). This results in unequal lengths of curve before and after the PVI, typically used when design constraints require different approach and departure grades or limited space. (Type: BOOLEAN, Cardinality: R) |
Part: Vertical Curve Lengths
- Purpose: Describe the purpose of the Vertical Curve Lengths part
Concept: Vertical Curve Lengths Information
- Purpose: Describe the purpose of capturing Vertical Curve Lengths information
Provide a table with the set of information requirements for each concept. Extend the table as needed.
| Idea | Explanation |
|---|---|
| Length of Vertical Curve | The horizontal distance in feet from the PVC to the PVT. (Type: REAL, Units: Feet, Cardinality: R) |
| Middle Ordinate Vertical | the maximum distance between the midpoint of the curve and the midpoint of the long chord. (Type: REAL, Units: Feet, Cardinality: R) |
Part: Vertical Alignment Key Stations and Elevations
- Purpose: Describe the purpose of the Vertical Alignment Key Stations and Elevations part
Concept: Vertical Alignment Key Stations and Elevations Information
- Purpose: Describe the purpose of capturing Vertical Alignment Key Stations and Elevations information
Provide a table with the set of information requirements for each concept. Extend the table as needed.
| Idea | Explanation |
|---|---|
| Point of Vertical Curvature Station | The station of the point at which a tangent grade ends and the vertical curve begins. (Type: REAL, Units: Stationing, Cardinality: O) |
| Point of Vertical Curvature Elevation | The elevation of the point at which a tangent grade ends and the vertical curve begins. (Type: REAL, Units: Feet, Cardinality: O) |
| Point of Vertical Intersection Station | The station of the point where the extension of two tangent grades intersect. (Type: REAL, Units: Stationing, Cardinality: O) |
| Point of Vertical Intersection Elevation | The elevation of the point where the extension of two tangent grades intersect. (Type: REAL, Units: Feet, Cardinality: O) |
| Point of Vertical Tangency Station | The station of the point at which the vertical curve ends and the tangent grade begins. (Type: REAL, Units: Stationing, Cardinality: O) |
| Point of Vertical Tangency Elevation | The elevation of the point at which the vertical curve ends and the tangent grade begins. (Type: REAL, Units: Feet, Cardinality: O) |
| High Point Station | The station at the highest point on a curve where the gradient changes from positive to negative. (Type: REAL, Units: Stationing, Cardinality: O) |
| High Point Elevation | The elevation at the highest point on a curve where the gradient changes from positive to negative. (Type: REAL, Units: Feet, Cardinality: O) |
| Low Point Station | The station at the lowest point on a curve where the gradient changes from negative to positive (Type: REAL, Units: Stationing, Cardinality: O) |
| Low Point Elevation | The elevation at the lowest point on a curve where the gradient changes from negative to positive (Type: REAL, Units: Feet, Cardinality: O) |
| Point of Vertical Curvature Station | The station of the point at which a tangent grade ends and the vertical curve begins. (Type: REAL, Units: Stationing, Cardinality: O) |
| Point of Vertical Curvature Elevation | The elevation of the point at which a tangent grade ends and the vertical curve begins. (Type: REAL, Units: Feet, Cardinality: O) |
| Point of Vertical Intersection Station | The station of the point where the extension of two tangent grades intersect. (Type: REAL, Units: Stationing, Cardinality: O) |
| Point of Vertical Intersection Elevation | The elevation of the point where the extension of two tangent grades intersect. (Type: REAL, Units: Feet, Cardinality: O) |
| Point of Vertical Tangency Station | The station of the point at which the vertical curve ends and the tangent grade begins. (Type: REAL, Units: Stationing, Cardinality: O) |
| Point of Vertical Tangency Elevation | The elevation of the point at which the vertical curve ends and the tangent grade begins. (Type: REAL, Units: Feet, Cardinality: O) |