When it comes to advances in technology, young adults are often the first to embrace change. But it’s the 50-plus crowd that could end up as early adopters of a coming revolution in transportation: self-driving cars.

Most major auto makers already are testing such vehicles. In May, Google, the Mountain View, Calif., search giant, which has pioneered the self-driving idea, unveiled its latest prototype car—with no steering wheel, and no accelerator or brake pedals.

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