CARACAS (Reuters) - Venezuela on Friday began a census of car owners, a move the socialist government says will help determine a “rational” use of fuel but critics warn could lead to rationing in the crisis-stricken OPEC nation.

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Fuel shortages are already frequent in Venezuela, where a fifth straight year of a brutal recession has led to refinery outages and steep falls in oil production.

President Nicolas Maduro over the weekend said Venezuela needed “rational” gas use and that a census was “the answer to that.” One top party official also proposed increasing the price of highly subsidized fuel, the world’s cheapest.

Details of the government’s plans are scarce and the Information Ministry did not respond to a request for comment, but Venezuelans have fretted that the census could be setting the stage for more restrictive gasoline sales.

“I am registering myself because I am scared that if I am not in the census, they will not sell gasoline to me,” said taxi driver Juan Suarez, 45, who had spent six hours in line in downtown Caracas on Friday. He and others in the line said they also hoped that being registered could grant them access to cheaper gas.

But dozens of truck drivers blocked streets in Caracas to reject the census they say will not solve chronic shortages that have decimated the number of functioning buses, forcing many poor Venezuelans to rely on precarious flatbed trucks to get around.

“We have not received the tires and lubricants we need to be able to work. The problems of transport workers will not be solved with this census,” said Jose Luis Trocel, the head of the main transport workers union, as he drove toward the Transport Ministry to stage the protest.

Under the census, car owners had to use a government-issued “fatherland card” to register details of their vehicle and gasoline consumption online. They then had to line up at government offices to scan the card.

Venezuelans who do not have the card cannot participate. Anti-Maduro politicians say that marginalizes government opponents who have refused to get the card the government now uses in distribution of everything from food to bonuses.

“They ruined Venezuela. They destroyed (state oil company) PDVSA and now they are trying to ration fuel sales through the fatherland card in the country with the biggest oil reserves of the Western Hemisphere. Say no to this blackmail,” tweeted opposition lawmaker and economist Jose Guerra.