> For the complete documentation index, see [llms.txt](https://docs.openbrim.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.openbrim.org/developers/paramml-developer-guide/core-objects/alignment-object/horizontal-segments.md).
# Horizontal Segments
Each "Alignment" object must have at least one object to define the horizontal control line. Multiple segments can be combined to define the full horizontal alignment of the road. Multiple segments can be combined to define the full horizontal alignment of the road.
Horizontal segments are used to design the route between the two predetermined stops in the plan. The elements of "**Alignment**," "**Horizontal Curve**," and "**Transition Curve**" can be utilized in defining the horizontal segments. The road design takes into account ergonomics and cost efficiency and employs a combination of these elements accordingly.
**Example:**
```xml
```
 To view this example in the library, see ()
**Parameters of Straight Object:**
The T=""straight" object is used to define straight segments in the horizontal alignment and can only be included within an "Alignment" object.
| **Label** | **Mandatory** | **Name and Type Attributes** | **Default Description and Value Attributes** | **Other Attributes** |
| --------- | ------------- | ---------------------------- | ----------------------------------------------------- | ---------------------------------------- |
| Length | Yes | N="Length" | D="Length: The length of the straight segment." V="0" | Role="Input" UT="Length" UC="Coordinate" |
**Parameters of Circular Object:**
The T="Circular" object is used to define a curved (Alignment), circular portion of the horizontal alignment.
\| | **Label** | **Mandatory** | **Name and Type Attributes** | **Default Description and Value Attributes** | **Other Attributes** | | --- | --- | --- | --- | --- | | 1 | Length | Yes | N="Length" | D="Length: The length of the circular segment." V="0" | Role="Input" UT="Length" UC="Coordinate" | | 2 | Radius | Yes | N="Radius" | D="Radius: The radius of curvature for the curve segment." V="0" | Role="Input" UT="Length" UC="Coordinate" | | 3 | Direction | Yes | N="Direction" | D="Direction: The direction of the curve at start looking up-station. \[Left=LEFT/Right=RIGHT]" V="LEFT" | Role="Input" |
**Parameters of Sprial Object:**
The T="Spiral" object is used to define transitional segments in the horizontal alignment.
\| | **Label** | **Mandatory** | **Name and Type Attributes** | **Default Description and Value Attributes** | **Other Attributes** | | --- | --- | --- | --- | --- | | 1 | Length | Yes | N="Length" | D="Length: The length of the spiral segment." V="0" | Role="Input" UT="Length" UC="Coordinate" | | 2 | Direction | Yes | N="Direction" T="Text" | D="Direction: The direction of the spiral at start looking up-station. \[Left=LEFT/Right=RIGHT]" V="LEFT" | Role="Input" | | 3 | Start Radius | Yes | N="RadiusStart" | D="Start Radius: Optional radius at the start of spiral segment. Ignored if spiral follows a circular curve." V="0" | Role="Input" UT="Length" UC="Coordinate" | | 4 | End Radius | Yes | N="RadiusEnd" | D="End Radius: Optional radius at the end of spiral segment. Ignored if spiral follows a circular curve, or Start Radius is specified." V="0" | Role="Input" UT="Length" UC="Coordinate" |
---
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