The different TA models differ in terms of clients and financial backers, whether the studies are carried out by the institute itself or by external bodies, and the extent of public involvement.
The classical TA model is the one wich was used by the US Office of Technology Assessment (OTA) until it ceased to exist in 1995. Is noted for its expert orientation, high in-house expertise, and the indirect involvement of the relevant interest groups. As an office of Congress it was closely linked to the legislative branch. Today the classical model is particularly represented by the Office of Technology Assessment at the German Parliament (TAB)
TA Swiss may be regarded as a prototype model TA secretariat. Here a relatively small team attached to the Swiss Academies of Science has the legal duty to advise parliament and government. Studies are carried out by external experts on the basis of public tenders; participatory projects are implemented by the secretariat itself.
The participatory model is typified by the Danish Technology Board (DBT). This institute is also linked to parliament, but its main focus is on mediating a general social discussion of technological development. The model is characterised by its low level of in-house research and the high priority given to public participation.
This contains the elaboration of working documents for administrators, the provision of decision-making aids for parliament, and the organisation of an information and opinion-forming process for the public. Large-scale TA studies are an essential prerequisite for all these tasks.
The ITA largely follows the classical model, but has recently also carried out a number of participatory procedures. All three models fulfil different roles within a modern democracy.
Internationally there are two networks of TA institutions: the German-speaking Netzwerk Technikfolgenabschätzung (NTA) and the network of European Parliamentary Technology Assessment (EPTA) institutions. A number of TA institutions have formed the European Technology Assessment Group (ETAG) to advise the European Parliament.