Automobile manufacturers who began two decades ago to design passenger vehicles that were more fuel-efficient faced a dilemma in the fact that the lighter, more efficient vehicles were less safe on high-speed highways  However, the manufacturers avoided this dilemma by producing two types of passenger vehicles: a lighter vehicle for medium-speed, local transportation, and a heavier, safer vehicle for long-distance travel
Since most automobile traffic is local, a net savings in fuel use was achieved with no loss in safety
Some automobile manufacturers designed prototypes for fuel-efficient passenger vehicles more than two decades ago.