Highway alignment:  

The position or layout of center line of highway on ground is called the highway alignment. Highway alignments includes both horizontal and vertical alignment of roadway. The horizontal alignment includes straight path, horizontal deviation and curves while vertical alignment includes vertical curves gradients etc.

A new road should be aligned carefully as improper alignment would result following disadvantage.

• Increase in construction cost
•  Increase in maintenance cost
•  Increase in vehicle operation cost
• Increase in accident rate

Requirements of good highway alignments
Short: The alignment between two terminal stations should be short and as far as possible. But due to some practical considerations deviations may be needed. Short alignment can reduce the vehicle operation cost and also save the time.

Easy: The alignment should be easy to construct and maintain. Also the alignment should be easy for the operation of vehicles with easy gradients and curves. 

Safe: Alignment should be safe enough for construction and maintenance from the Highway Engineering: Grade 10 13 viewpoint of stability of natural hill slopes, embankment and cut slopes and
foundation of embankments. Except that, it should be safe for the traffic operation with safe geometric features.

Economical: Highway alignment should be economical as far as possible. Alignment could be considered economical only ,if the total cost including initial cost ,maintenance cost and vehicle operation cost is lowest.ie least earthwork, use of locally available materials, least fuel consumption, least wear and tear of vehicle parts, least maintenance cost and maximum use to the population.

Factors which controls the highway alignment:

The various factors which controls the highway alignment are as follows:
1. Obligatory points
2. Traffic
3. Geometric design
4. Economics
5. Other considerations

1.Obligatory points are specific locations or features that a highway must either pass through, connect to, or avoid, and they significantly influence the alignment (route) of the highway.

Types of Obligatory Points: Obligatory points may be divided into two categories:

a). Point through which alignments has to pass : Some examples of point through which alignments has pass are

• Alignment along the hill side pass.
•  Alignment to suit proper location of bridge.
•  Alignment to connect intermediate place.
•  Alignment to connect industrial area or zone

b). Points through which alignment should not pass: Some examples Points through which alignment should not pass are 

• Historically and archeologically important property.
•  Restricted zone for defense, national security.
•  Costly structural elements requiring heavy compensation.

2.Traffic: In the context of highway engineering, traffic refers to the movement of vehicles and pedestrians along roadways. It includes the volume, type, speed, and pattern of movement, and is a critical factor in planning and designing highways.