You can change the tangency and parameter constraints of alignment lines, curves, and spirals.
When you create an alignment, you define the geometry of each line, curve, and spiral by specifying a set of parameters, or constraints. After an entity is created, you can only edit the parameters that affect the specified constraints. The alignment layout honors the constraints, even if the geometry of adjacent entities is changed.
As you edit the alignment, you can change the constraints for each entity as needed.
There are two types of alignment constraints that you can change:
Tangency Constraints
A tangency constraint is a parameter that can constrain an entity's geometry to the geometry of an adjacent entity.
There are four tangency constraints:
Not constrained (Fixed) 
Constrained by Previous (Floating) 
Constrained by Next (Floating) 
Constrained on Both Sides (Free)
The manner in which an entity can be edited may be restricted by its tangency constraint. For example, an entity that is constrained on both sides will always maintain tangency to the entities that are immediately before and after it, even if one of the adjacent entities is moved.
You can specify that if an entity's tangency constraint is changed, the tangency constraints of adjacent entities will be changed so that tangency is maintained.
Parameter Constraints
Parameter constraints are the parameters by which an entity was constrained to when it was created. Following are examples of parameter constraints:
- pass-through points
- radius
- length
- angle
Parameter constraints may be locked for either each entity, or for all entities in an alignment.
- Locked: The Parameter Constraint cannot be changed. Only the parameters permitted by the Parameter Constraint can be edited.
- Unlocked: The Parameter Constraint can be changed, which enables a wider variety of parameters to be edited.