Even though there is a high likelihood of future fuel constraints due to capacity limitations, there is little knowledge about the impacts on the economy and freight transport. This research used Input-Output (I-O) analysis to model the relationship between fuel constraints and economic impacts. The total reduction of financial flow imposed on the economy by peak oil was calculated through the supply constrained I-O model. The Leontief price model (LPM) was used to calculate the impacts of a fuel price increase. Initially, the monetary relationships and the economic trade among the different sectors and regions of New Zealand were analysed through the I-O and MRIO (Multi-Regional Input-Output) models. In terms of individual industries, the 51 sectors I-O table indicates that the most significant industries were service industries: trade, construction, housing, and finance and insurance. This analysis contradicts the widely stated view that the New Zealand economy is based on tourism, primary industries and international trade. The economic trade relates to the physical trade, as the exchange of money between regions corresponds to the trade of goods and services observed in the real world. The physical trade describes the transport activities. The outputs of the I-O and MRIO models were used to model freight transport. The literature review indicated that combined models were more suitable to this research, as they can be linked to I-O models, allowing one to perform trip generation, followed by simultaneous trip distribution and assignment. Such an approach guarantees that equilibrium is reached and the errors are minimized. This model can reproduce well the current freight transport movements among regions, and the impacts of fuel constraints can be assessed using the result of the MRIO model after the application of a fuel constraint. While fuel constraints can happen due to many reasons (e.g. strikes, natural disasters and trade barriers), the focus of this thesis is the Peak Oil scenario, in which no excess capacity will be available. Due to its transitional nature, no immediate adjustment will likely take place within the economic system. The mixed I-O model allows for the estimation of reductions in outputs given defined constraints in selected sectors (in the case of this research, the fuel sector). Fuel constraints were estimated in physical terms (approximately 2% reduction per annum) and financial terms (total reduction of financial flow imposed upon the economy by peak oil). The monetary constraint analysis was performed using the LPM and assuming a 100% fuel price increase. It was observed that the mixed I-O showed insensitivity to a small change in fuel availability. The LPM, on the other hand, showed higher impacts than the mixed I-O. The most affected sectors were fuel intense sectors, such as mining, fertilizers and transport related services. Assuming that the economic trade between regions can well describe the freight transport movements, the overall impact reduction in transport flows was estimated at 0.07%. This value indicates no significant impact on trip distribution and traffic flows, so a new transport model was not necessary.