trafikkfordeling

Trafikkfordeling refers to the process of distributing travel demand across the available routes and modes within a transportation network. It is a central component of travel demand modeling and is typically performed after trip generation and trip distribution, producing an origin-destination matrix that shows how many trips occur between each pair of zones and, in some cases, by mode and time of day.

The main idea is to reflect how trips are spread geographically given the network’s impedance, such as travel time, cost, and distance, as well as socio-economic factors. Common models include gravity models, which estimate flows as proportional to zone productions and attractions and inversely related to impedance, and radiation or intervening opportunities models. In more advanced analyses, the distribution is often coupled with route choice in a two-step process: first estimate OD flows, then assign trips to specific routes based on expected travel times and congestion.

Data and methods: Inputs typically include zone productions and attractions, an impedance matrix (travel times or generalized costs), and sometimes mode shares. Calibration may be performed against observed traffic counts or OD matrices. Techniques such as iterative proportional fitting and logit-based approaches are used to refine distributions, especially when incorporating mode choice and varying costs.

Applications and limitations: Trafikkfordeling informs transport planning, congestion management, and impact assessments for new infrastructure or policy changes. Results depend on data quality and model assumptions and are subject to uncertainty. Regular validation and updating with new data are important to maintain reliability.