The aim of this report is to answer the question: what are the environmental effects of construction and improvement of transport infrastructure on a national scale ? Three causes of environmental effects are distinguished: (1) the new or improved infrastructure generate traffic, (2) the new or improved infrastructure attracts traffic that without the improvement would have used another kind of infrastructure (substitution), and (3) construction and maintenance of new infrastructure requires energy. The issue of induced traffic on new infrastructure is controversial. Theoretical considerations, empirical studies and model estimates indicate that extra road capacity result in a greater volume of traffic. In this report a main road lane kilometre eleasticity for car use is estimated of 0.15-0.6 for The Netherlands. High-Speed Rail will result in generation and substitution of traffic. Empirical evidence and model estimates indicate that some 30% of HSR passengers will be generated. The other passengers will be diverted from air, car and other trains. Based on theoretical considerations it is indicated that a new freigh rail infrastructure in The Netherlands (`Betuwelijn') will not generate much transport; most of the transported goods will be diverted from road and water infrastructure. In this report a rough calculation is made of the environmental effects of construction and improvement of main infrastructure in The Netherlands in the period 1995-2020. It is indicated that: (a) on a national scale the expected construction and improvement of main infrastructure will increase the environmental pressure of transport. Without the infrastructure improvement energy use of transport in 2020 will be 2-6% lower; and (b) this increase is caused by the expected extension of road infrastructure in the period 1995-2020 which will lead to induced traffic. Construction of High-Speed Rail and a new freight rail will result in a somewhat lower energy use, but this effect is very small compared to the increase of energy use because of the road infrastructure extention. (A)
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