The Globe and Mail reports in its Thursday edition that one of the world's largest experiments in driverless cars suffered an embarrassing setback as a number of robot taxis abruptly stopped moving in traffic Tuesday in Wuhan, China, stranding their passengers and sometimes blocking other vehicles. A New York Times dispatch to The Globe says police in Wuhan announced Wednesday that it had received a "succession" of reports that self-driving cars had stopped. The cars were part of the extensive Apollo Go program of self-driving cars run in Wuhan by Baidu Inc., a large Chinese Internet company. The police said a "system failure" had occurred, and did not say how many cars had been affected. Baidu has hundreds of the cars in Wuhan. Waymo LLC, an American provider of robot taxis, had a somewhat similar incident in December in San Francisco, when an hours-long power failure prompted Waymo cars there to pull over and stop. Robot taxis are typically programmed to stop if they encounter an unfamiliar situation. In July, tests on 36 car models from 20 brands found that slightly fewer than half the cars could safely avoid a crash when they encountered trucks near a construction site at night. Tesla models proved most reliable.