This paper presents a simplified method of assessing the impact of a motorway under construction on arable lands. The method developed makes it possible to determine all the losses resulting from and connected with the indicated problems of the motor-way impact. A basis for the determination of losses studied is the analysis of variations in land use, soil quality classes, and in the layout of agricultural roads along the axis of the designed motorway. It is assumed a measure of the multilateral impact of motorway on arable lands; this measure is a specific variant of lands value. The specificity of this value variant lies in the fact that while determining it, only the variation in the usefulness to agricultural production is assessed. Therefore, it is a measure to valuate arable land usefulness in the agricultural production. Thus, this assumed measure of the motorway impact is not a market value. The estimated land value will be close to its market value only in typical agricultural regions where the key parameter to mould the land price is production potential of such lands. The presented method of assessing the motorway impact on arable land is exemplified by a section of ‘A-4’ motorway; this section is about 7 km long, it runs between two towns: Cikowice and Bochnia. One kilometre of the motorway constructed will result in the decrease of the arable land value by 2468 corn units. The value of arable land will decrease by around 80% in total owing to taking over lands for the construction of motorway, and because of the toxic impact of the motorway on soils. The remaining 20% of losses in the land value results from the increase in the transport and from the deteriorated spatial arrangement of plots.