An approach to determine the frequency of bridges in an urban context: The case of European cities

The purpose of this paper is to determine the existence of a possible expected bridge frequency (number of bridges per unit of measurement) in an urban context. To achieve this, a method was developed to calculate the real frequency of crossing points already built over water bodies in inner cities. The method was based on collecting different measurable data of different cities using images from Google Earth. Furthermore, this method was applied to evaluate bridges built in several European cities that have a river. The results show that there is a clear link between the frequency of urban bridges and the width of the river, expressed by a power law function which defines bridge frequency as an inverse function of river width. Also, there is no direct link between the size of the city and the number of crossing points built in the city. Additionally, two new urban development projects on rivers were evaluated by using the defined power law function. Thus, it was concluded that future urban development close to rivers could use this function to decide the number of new crossing points. Furthermore, the ideal distance between consecutive urban bridges has been determined.