In Mexico's booming auto industry, the cars rolling off assembly lines may look identical, but how safe they are depends on where they're headed.

Vehicles destined to stay in Mexico or go south to the rest of Latin America carry a code signifying there's no need for antilock braking systems, electronic stability control or more than two air bags - if any - in their basic models.

If the cars will be exported to the United States or Europe, however, they must meet stringent safety laws, including as many as six to 10 air bags and stability controls that compensate for slippery roads and other road dangers, say engineers who have worked in Mexico-based auto factories.

Because the price of the two versions of the cars is about the same, the dual system buttresses the bottom lines of automakers such as General Motors and Nissan. But it's being blamed for a surge in auto-related fatalities in Mexico, where laws require virtually no safety protections.

"We are paying for cars that are far more expensive and far less safe," said Alejandro Furas, technical director for Global New Car Assessment Program, or NCAP, a vehicle crash-test group. "Something is very wrong."

In 2011, nearly 5,000 drivers and passengers in Mexico died in accidents, a 58 per cent increase since 2001 according to the latest available data from the country's Transportation Department. Over the same decade, the US reduced the number of auto-related fatalities by 40 per cent. The death rate in Mexico, when comparing fatalities with the size of the car fleet, is more than 3.5 times that of the US.

Nevertheless, Mexico hasn't introduced any safety proposals other than general seat-belt requirements for its 22-million strong auto fleet. Even then, the laws don't mandate three-point shoulder belts necessary to secure child safety seats.

Brazil and Argentina, on the other hand, have passed laws requiring all vehicles to have dual front air bags and antilock braking systems by next year.

An Associated Press investigation this year found that Brazil's auto plants produce cars aimed at Latin American consumers that lack basic safety features. Like Brazil, Mexico doesn't run its own crash test facility to rank cars' safety before they hit the road.

Dr Arturo Cervantes Trejo, director of the Mexican Health Ministry's National Accident Prevention Council, said the country has a long way to go to upgrade safety standards, but challenging the nation's US$30 billion auto industry could be difficult.

- AP