Importance of Highway Capacity, Also explain Practical Capacity

 

Importance of Highway capacity

                              Traffic capacity is the estimation of number of vehicles that can pass through a specific location in a unit time, usually one hour. It is an important characteristic of traffic engineering. Highway capacity will determine that, how many vehicle a specific road can accommodate during its peak hours. During the design of highways, and roads, traffic demand is calculated from statistical analysis and on the basics of traffic demand, the number of lanes, lane width, and other road parameters are designed and finally the traffic capacity is calculated and compared with the traffic demand.

It is the maximum hourly rate at which vehicles can reasonably be expected to cross a point on a roadway during a given time period under prevailing traffic roadway and control condition. For multi lane highway it is 2000pcphpl, and for 2-lane highway is 2800pcph (passenger car per hour).

Units: vph (vehicle per hour or vphpl (vehicle Per hour per lane)

Practical capacity

Practical capacity  is the maximum number of vehicles that can passes through a specific location during unit time under normal conditions, (without causing any unreasonable delay, hazard or restriction). It is an important characteristics with a strong interest in a designer striving to provide adequate space for a highway, too hence this is also called "design capacity"

The following are the important factors that affect the practical capacity of a traffic lane.

1. Lane Width
2. Lateral Clearance
3. Width of Shoulder
4. Commercial Vehicles
5. Alignment
6. Presence of Intersections at Grade