Distance-decay functions for daily travel-to-work flows

•We model distance-decay function on the example of the travel-to-work flows.•We identify specifics of the distance-decay function for selected centres of the Czech Republic.•We propose a new parameter, radius of influence of selected centres, on the basis of the distance-decay functions.•We propose a universal distance-decay function based on the population and number of jobs in the centres. The non-homogeneity of geographic space brings about the processes that horizontally relate sections of geographic space, in transport geography referred to as spatial interactions. The distance separating different types of locations plays a crucial role in these interactions. Distance is the major factor that influences the values of interaction intensities. The question is how the intensities decrease with distance, since this decrease is usually not linear. This paper pursues the issues of the shape and parameters of the distance-decay functions based on daily travel-to-work transport movements, taking regional centres in the Czech Republic as the example. First the special distance-decay functions for individual regional centres are presented and discussed, followed by the expression of the universal distance-decay function approximating generally to the traits of the Czech settlement system and the nature of the interaction flows, i.e., travel-to-work. The expression of the universal function is based on the application of two easily accessible variables: population and number of jobs.