Railway freight transportation presents a degree of complexity which frequently makes impossible to model it with sufficient precision. Currently, energetic and environmental impacts of freight transportation are usually modelled following average data, which do not reflect the characteristics of specific lines. These models allow qualitative approximations which may be used as criteria for designing high-level transportation policies: road-train modal shift, regional energetic planning or environmental policies. This paper proposes a methodology for estimating railway consumption associated to a specific railway line which yields a new degree of precision. It is based on estimating different contributions to railway consumption by a collection of factors, mobility, operation, or infrastructure-related. This procedure also allows applying the methodology for designing transportation policies in detail: evaluating impact of modal shift, consumption and pollutant emissions on a specific line, as well as the effect of building tunnels, reducing slopes, improving traffic control, etc. A comparison of the estimations given by the conventional approach and the proposed methodology is offered, as well as further comments on the results. (C) 2009 Elsevier Ltd. All rights reserved.