Modify the length of the bridge between abutments by changing the start and end station locations.
Bridge length is reported in the Geometry section of the Stack, as well as in-canvas.
Click the start or end station gizmo to select it.
Click and drag-and-drop the start or end station gizmo along the path of the road to modify the length of the bridge. Click again to place the new location of the start or end station. Press Enter to regenerate the bridge.