Protection device for a vehicle against an impact

Device for vehicle (5) has inflatable element (1) which once inflated fits general shape of vehicle zone to be protected. Device has casing (2) which is deployed using inflatable frame (3) having volume capacity much less than casing volume. Pressurizing and deploying inflatable frame ensures rapid deployment of casing and simultaneously causes filling with air of internal volume of inflatable element through non-return valve carried by casing.