The GNR military is pulling over motorists entering the country to ensure the smooth running of an obligatory questionnaire for the National Institute of Statistics.
Questions, including the names of driver and occupants, destination, length of visit and the amount of money that visitors are planning to spend, are being asked at Portugal's road entry points, ports and airports.
Remarkably, the survey is not voluntary as it is required by law to enable the Institute to gather information on tourism.
The exercise involves the GNR whose personnel have been deployed to pull over vehicles so that Institute surveyors can ask their questions. The interviewers also want to know if the vehicle recently filled up with fuel in Spain, not perhaps a question that relates too closely to tourism.
"The National Institute of Statistics, in cooperation with Tourism of Portugal, is conducting the Survey on International Tourism which runs until the end of 2016," said the Institute spokesman.
"This is an official statistical operation developed in accordance with the law covering national statistical systems and it is mandatory to answer questions,” said the organisation.
The method chosen is "by conducting face to face interviews with travelers at the main borders - air, sea and road," said the Institute.
On the roads, the GNR is selecting and stopping cars to allow the interviewers to ask their questions. The GNR are only there to ensure the safety of interviewers and reinforce the legality of the operation.
The Institute wants to estimate the number of residents and non-residents crossing the main national borders, to know the profile of the travellers and their routes, and to get an idea what they are going to be spending.
Turismo de Portugal say they will use the questionnaire findings in the planning of their activities and have no comment as to the effects such intrusion will have on driver and passenger attitudes before and after being hauled over.