While the oil shock certainly affected sales, many far more profligate cars were introduced at the same time the SM ceased production, including the hydropneumatically suspended Mercedes-Benz 450SEL 6.9. Peugeot even introduced a V6 powered car of similar displacement and fuel consumption in 1975, the 604. In the U.S. (the main export market for the SM), the SM was actually an economical vehicle relative to its competitors. However, the U.S. National Highway Traffic Safety Administration (NHTSA) imposed new automotive design regulations in 1974, effectively banning the Citroën from the U.S. market.