The report highlights four important tasks for CATRIN. o To provide more evidence on the relationship between marginal cost (MC) and average cost (AC), i.e the cost elasticity. Ultimately this relationship will define the rate of cost coverage from marginal cost based charges. o To improve the knowledge on the shape of the cost curve (decreasing versus increasing). The shape of the MC curve will define the MC based price and rate of cost coverage for infrastructure with different levels of traffic demand and thus explain regional differences. o To increase the knowledge of marginal cost in relation to different vehicle types. For this differentiation the CATRIN case studies include a meta-analysis of engineering experience in the field of infrastructure deterioration. o To improve the comparability of results between different studies and ensure a clear classification of cost items included. An important characteristic of research on marginal cost estimation for infrastructure is the lack of sufficiently detailed data on the cost of maintaining, operating and renewing transport infrastructure as well as on the use of infrastructure across all modes of transport. It appears that for applying state-of-the-art estimation methods, researchers have to allocate a considerable bulk of time and resources to collect this type of data. This will also hold true for the CATRIN case studies. While a general improvement of the data situation is a task for the administrations in the sector and cannot be subject of a research project like CATRIN, the CATRIN case studies have to anticipate this problem and should care for a thorough documentation of data collection including a precise definition of the type of data collected.