Methods for Determining the Decisive Traffic Demand for the Planning and Dimensioning of Roads

Problem Statement

The objective of traffic facility design is to ensure that a traffic facility is dimensioned in such a way that it can handle the expected traffic demand. Since this traffic demand is not evenly distributed over time, but fluctuates (largely periodically), either a longer period with fluctuating traffic demand must be considered for the design (period analysis, e.g. "all-year analysis") or a specific demand situation is selected for which the design is carried out as a proxy (design traffic volume of a representative hour, e.g. "n-th hour."). These methods are difficult to use in practice because the necessary measurement data are often missing or cannot be obtained with economically justifiable effort. Under these circumstances, the design traffic volume must be estimated from the available data.

Another major uncertainty in the design of a traffic facility also lies in the determination of future traffic demand.


The aim of this research project is to compare and evaluate different approaches [= design concepts] for estimating the traffic demand of the n-th hour and for determining a traffic demand that is considered decisive for the design of new, reconstructed and expanded roads on the basis of extensive statistical evaluations of traffic data.

The project results are to be prepared for adoption in the regulations and as specifications for the evaluations in the traffic statistics. The focus is on the extra-urban road network. The usability of the design concepts for urban networks will be discussed.


As part of the project, interviews will first be conducted with practitioners in order to obtain an overview of the application and handling of the topic of decisive traffic demand in practice. Requirements for potential new design concepts will be defined and, based on this, new design concepts will be developed accordingly. In order to check and evaluate the design concepts, they are calculated on the basis of a comprehensive traffic database for a large number of traffic facilities.

The IfV is responsible for the development of the traffic database and the subsequent calculation of the concepts for review and evaluation. The traffic database is composed of permanent counting station data provided by the BASt and the federal states of Hessen and Nordrhein-Westfalen. For this purpose, this data must be converted into a uniform format and, if necessary, plausibility-checked and aggregated.