Roadway Capacity In Highway Design

Roadway Capacity depends on the traffic volume. Traffic volume can be served at each level of service are referred to as "Service flow rate".Once each level of service has been chosen for particular design, the corresponding service volume logically becomes the 'design service volume'. It indicates that if the traffic volume using the facility exceeds design service volume, the operating conditions of the roadway will be in inferior to the level of service. The level of service appropriate for various various type of roadways are given below:

	Type of Area and Appropriate Level of Service
Highway Type	Rural Level	Rural Rolling	Rural Mountainous	Urban and Suburban
Freeway	B	B	C	C
Arterial	B	B	C	C
Collector	C	C	D	D
Local	D	D	D	D

Level of service = General Operating Condition

A = Free Flow

B = Reasonably Free Flow

C = Stable Flow

D = Approaching Unstable Flow

E = Forced or breakdown flow.