corporate boss Elon Musk has tweeted that shopping mall , parks and crossroads with complex traffic light systems are the biggest challenges facing the city 's autonomous vehicle technology , and it would require a " massive upgrade " to achieve 99.9999 % safety . Musk also cited the end of 2020 as his deadline to have one million robo - taxis on the roads .
Tesla boss Elon Musk has tweeted that shopping mall car parks and crossroads with complex traffic light systems are the biggest challenges facing the firm's autonomous vehicle technology, and it would take a "massive effort" to achieve 99.9999% safety. Musk also specified the end of 2020 as his deadline to have one million robo-taxis on the roads.