An outline for a validation database for SAMGODS

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Magnus Johansson

A new Swedish national goods transportation model, SAMGODS, has been developed through collaboration among Swedish transport authorities. As the model recently has begun to be applied to real world problems, the need for a validation database has increased. The purpose of such a database is to facilitate validations of the model. The current paper presents a pilot study to create a validation database for SAMGODS. The study focuses on two areas: available data sources that may provide validation data, and how to carry out the validation in practice. The latter is of particular importance since a large number of practical problems arise when matching SAMGODS output data with the validation data. Worth mentioning among the problems that arise are: the inhomogeneous structure of the data tables, the often differing aggregation levels between model output data and validation data, differing time periods, differing systems for commodity groups and elasticities not being immediately available from the SAMGODS data. Other complicating issues are handling of confidential data and the large quantities of data. In this report, a relatively detailed proposal for the design of a validation database is put forward. However, the proposed design is not limited to SAMGODS output data, but it is hoped to be sufficiently flexible to comprise also other goods transportation data from future regional or local models. One of the main ideas in designing the database has been to develop a uniform and flexible data table format in which all relevant data can be stored. This format greatly facilitates the matching between SAMGODS output data and the validation data. Other problems and associated possible solutions are thoroughly discussed.

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