Numerous works have addressed the problem of the hedonic modelling of housing prices, in which structural and locational variables of dwellings are considered. Among the latter, it is common to include variables related to transport accessibility. However, few studies have considered the effects of proximity to railway lines, and even less so freight railroads. This study determines the size of the width of influence (buffer zone) of negative externalities associated with the freight train line in the city of Santa Marta, Colombia. Moreover, the effect of this width on housing prices is studied. A hedonic model was estimated using spatial econometrics and geostatistical methods. Geostatistical techniques were used to obtain an isovalues map for the price of a standard dwelling. The study is of interest to the fields of real estate, territorial planning and transport systems, among others.