The 1970s in many ways was a transitional decade in the history of the automobile.
The biggest and most obvious transition was the phasing out of high speed muscle cars as omnipresent and a shift to safer, lighter and more economical vehicles. There were several reasons for these changes, some of which were driven by the energy crisis, as well as traffic casualties that called for stricter safety standards imposed on manufacturers. The environmental movement also played a key role in raising the public's awareness about how bigger engines cause more emissions. By 1979, you could see compact cars everywhere you turned.
During the 60s, muscle cars were very popular high speed sports cars that attracted much attention from fans of auto racing as well as vibrant youth culture. "Pony cars," such as the Ford Mustang and even the Chevrolet Trans Am, which were more compact versions of stylized high performance muscle cars, became popular leading into the seventies. Other pony cars included the Pontiac Firebird and the Mercury Cougar. The Challenger was Chrysler Dodge's luxurious answer to this trend starting in 1970. It was popularized by the 1971 movie "Vanishing Point" and the TV series "Mod Squad." The Challenger was available as a convertible until 1972. Although it was discontinued after 1974 due to declining sales of pony cars, the original Challenger has become a collector's item.
General Motors dominated the seventies, with its relentless top seller, the Chevrolet Impala, which was the number one vehicle most of the decade until its Cutlass Supreme Oldsmobile became a bigger seller toward the end of the decade through the early eighties. The third generation Cutlass Supreme was a midsize luxury vehicle. Convertible models were phased out after 1972, due to safety issues stemming from rollover accidents, though they’re making a comeback now. The final convertible of the decade, which is now a collector's item, was the Cadillac Eldorado, ending production after 1976.
Not quite the "impact" anyone wants, but the Ford Pintos changed history due to rear end explosions from traffic accidents, which by the end of the decade, became a wake-up call for all automakers to build safer vehicles.
The success of the VW Beetle in the sixties inspired a wave of smaller economy cars, from both Detroit and foreign manufacturers. Following the oil embargo of 1973, rising gas prices led to families shifting to more fuel-efficient cars, such as the Ford Granada, which was a smaller version of the Maverick. The Granada became Ford's top seller throughout the decade. The Ford Escort also helped usher in the new era, as well as economy cars from Honda and Toyota. Cadillac had been a status symbol for years, but since it only achieved 12 miles per gallon, it needed to evolve. So in 1975 GM issued the immediately successful Cadillac Seville, which was a smaller luxury vehicle, designed to compete with Mercedes Benz and BMW at a lower price.
Japanese cars started to make their influence strong in the 1970s. The Datsun Z Series, manufactured by Nissan, caught on with sports car fans throughout the seventies. The 280Z used fuel injection starting in 1975, which served to comply with growing government emissions regulations while increasing power.
This system cost less than a carburetor and was surfacing in other economy cars. By the end of the decade automakers began shifting to fuel injection to meet emissions regulations. Over the next few decades it was everywhere. People didn't necessarily enjoy it but it did the job.