This case study is dedicated to the estimation of marginal infrastructure costs of motorways in Germany. It focuses in its current stage on the marginal renewal cost. Exploring data availability for estimating also the costs of maintaining and operating motorways has not yet been completed1. The case study presented in this report makes use of a database on renewal costs developed within the UNITE project. This database has been extended by including information on factor input quantities and factor input prices which enables to estimate a full translog cost function. The analysis of motorway renewal costs presented in this paper was driven by two research questions. First, charging for the use of infrastructure has become an important issue in transport policy and requires scientifically sound quantitative information on the level of charges to be raised. In this context, the marginal cost of road maintenance and renewal is one component of optimal prices for road use. A second issue dealt with in this paper refers to the economic properties of the motorway renewal process such as factor substitution and the existence of economies of scale. The report is organised as follows: Chapter 2 briefly reviews the state of the art in estimating marginal road infrastructure costs. Chapter 3 discusses the methodological approach. Chapter 4 describes the input data used. Chapter 5 presents the estimation results and derives marginal renewal costs. Chapter 6 concludes.