Enticing though they are, such arguments conceal a logical flaw. As a classic 19th-century theory known as a Jevons paradox explains, even if autonomous vehicles eventually work perfectly — an enormous “if” — they are likely to increase total emissions and crash deaths, simply because people will use them so much.
Even if you perfectly solve crashes (doubtful, definitely not something that exists right now), the problems of microplastic pollution from tires and emissions from electricity generation are non-trivial.