Capacity

How much traffic can a facility carry? This is one of the fundamental questions designers and traffic engineers have been asking since highways were constructed. The term “capacity” has been used to quantify the traffic-carrying ability of transportation facilities. The value of capacity is used when designing or rehabilitating highway facilities to determine their geometric design characteristics such as the desirable number of lanes; it is used to design the traffic signalization schemes of intersections and arterial streets; it is used in evaluating whether an existing facility can handle the traffic demand expected in the future; it is also used in the operations and management of traffic control systems (ramp metering algorithms, congestion pricing algorithms, signal control optimization, incident management, etc.).