Horizontal Alignment

Horizontal Curves

For central angles smaller than 30 minutes, no curve is required.

The minimum curve length for central angles less than 10 degrees should be 240 m to avoid the appearance of a kink.

Above a 6000 m radius, a parabolic curve may be used. In no event should sight distance or other safety considerations be sacrificed to meet the above requirements.

ATTRIBUTES OF HORIZONTAL ALIGNMENT
Factors Influencing the Selection of Horizontal Alignment

 General Criteria
 Sight Distance Measurements for Horizontal Curves
 Horizontal & Vertical Alignment Coordination
 Striping No-Passing Zones 
 Intersecting Roads
 Utilities
 Transition (Spiral Curves)
 Circular Curves
 Superelevation
      Superelevation Transitions    
     Sample Calculation
     Superelevation Transition for 2 Lane Highway
     Rural Low Speed
     Urban Low Speed
     High Speed
     Superelevation Transition for Divided Highways
     Maximum Relative Gradient (English)
     Maximum Relative Gradient (Metric)
 Traffic Diversion Alignment
     Traffic Diversion Design