vägkapacitet

vägkapacitet is the term used in transportation planning to describe the maximum volume of traffic that a roadway can handle while maintaining acceptable levels of performance. It is generally expressed in terms of average daily traffic (ADT), vehicle hours of travel (VHT) or capacity per lane per hour.

The capacity of a lane depends on several factors, including lane width, pavement roughness, curvature, grade, and the mix of vehicle types. Driver behavior and traffic conditions such as acceleration, deceleration, and merging also affect the actual amount of traffic a lane can convey. Advanced microsimulation models estimate capacity by simulating individual vehicles, while empirical data from traffic counts and free‑flow observations provide calibration points.

Urban planners use capacity estimates to design roadway projects, assess the need for capacity expansion, and evaluate the impact of new development. Capacity studies are part of the broader field of performance‑based traffic engineering, which also incorporates traffic safety, environmental impact, and economic assessment. Capacity limits are often represented in the form of a "capacity index" that compares observed traffic flows to the theoretical maximum.

Current road design standards in Sweden, such as the Swedish Highway Authority’s guidelines, set specific lane and right‑of‑way dimensions that aim to achieve a target capacity of about 2,000–2,400 vehicles per lane per hour under normal conditions. Traffic management strategies, such as ramp metering, variable speed limits, and intelligent transport systems, can help maintain or temporarily increase capacity by smoothing traffic flow and reducing congestion.