Capacity of a highway

Before we discuss the capacity of a road pavement , the following terms may be clearly understood

1. Traffic valume - the number of vehicles moaving in a specified direction on a roadway that pass a given point during a specified unit of time , is called traffic volume 
2. Traffic density - the number of vehicles occupying a unit length of a roadway at a given instant, is called traffic density . It usually expressed as vehicles per kilometre 
3. Traffic capacity - the maximum number of vehicles in a roadway that can pass a given point in unit time, is called traffic valume 
4. Basic capacity - the maximum of passengers cars that can pass a given point on a roadway during one hour under the most ideal road and traffic conditions , is called basic capacity . It is something called theoretical capacity 
5. Practical capacity - the maximum no of vehicles that can pass a given point on a roadway during one hour without imposing any restriction to the driver's freedom for driving the vehicles, under prevailing roadway and traffic conditions , is called practical capacity . It is some times called design capacity.