Road alignment is the position occupied by the center line of a road in plan. The center line of the road is marked before its actual construction. The cost of construction, maintenance safety and ease in travel depends upon its alignment. Therefore a road alignment should be selected carefully. The basic principles of road alignment should be selected carefully.
1. The alignment of the road should be as short as possible to provide economy in the cost of construction.
2. The alignment should be as straight as possible which ensure higher speed to the traffic and lower cost of construction.
3. The alignment should be easy for construction, maintenance and traffic operation.
4. The alignment should cross the railway lines and other roads and bridges at right angles.
5. It should cross the rivers, canals or streams etc., at place where its width is minimum.
6. The alignment serves maximum population by connecting intermediate important towns and group of villages.
7. The alignment should pass through regions of natural beauty and scenery.
8. The alignment should be such that is crosses the minimum number of bridges, crossing culverts and embankment places.
9. It should provide smooth curves and easy gradient.
10. It should be such that minimum earthworks in embankment or cutting is done.
11. The alignment should provide good sight distance.
12. It should be free from obstruction like ponds, lakes, wells, monumental buildings and historical buildings etc.
13. The alignment should run through such places where materials of road construction and labor are easily available.
14. As far as possible it should run on good soil having good bearing capacity to bear the loads of traffic safely without any damage to the road.
15. The alignment should not run through much costly and cultivated land. It should also avoid forests.
16. The alignment should not have uneasy zig-zags in the way which reduces the speed of the traffic and increases accident possibility.
17. The alignment should not have lengthy straight routes to avoid monotony. Hence after certain length of straight routes (say 5km) of a road, a slight bend should be provided to break the monotony and to keep the drives alert.