The control of goods transportation growth by modal share re-planning: the role of a carbon tax

A simple model is proposed, at the macrolevel of variable aggregation, as a support for policy making in the control of goods transportation growth by possible alternative modes. The impact of feasible changes in the levying of "carbon tax" can be investigated with the proposed model, as well as the effects of investments in infrastructure and of the coverage of operational costs. Based on some transport externalities, various cost indices are identified and suitably minimized using optimization techniques, so that a quantitative definition of public policies can be derived. As an example, the model is used to evaluate an application of alternative policies in Germany. This case study shows that the model system of goods transportation has a slight sensitivity to the public interventions considered. The application of the carbon tax shows significant effects on the increase of fiscal revenues rather than on the reduction of carbon dioxide emissions and on the share of road transportation. Reductions in carbon dioxide emissions and in transportation by road are best achieved by higher investment in the infrastructures of alternative modes of transport, together with a reduction in fuel taxation.