The Air Cushion Restraint System (ACRS) was developed by General Motors in the early 1970s, and consisted of both a driver's and passenger's side air bag, along with a lap belt and status indicator light. The system was first installed in a test fleet of 1,000 1973 Chevrolet Impala 4-door sedans, painted in a unique green color. The exterior of these Impalas were identical to regular 1973 production models, but used a 1974-style Oldsmobile instrument panel and brand-new steering wheel design. The chassis of these cars were reinforced, and each Impala was equipped with a high-performance 350 cubic-inch V8 engine, the same one used in the Corvette.