A series of letters sent by autonomous-vehicle (AV) developers to Democratic US senator Ed Markey of Massachusetts sheds the most light yet on the human side of robot vehicle operations. In the documents, submitted to Markey as part of an investigation into self-driving-vehicle technology and released on Tuesday, seven companies, including Tesla, Amazon-owned Zoox, and Uber- and Nvidia-funded Nuro, released new details about their “remote assistance” programs. All the companies that responded to the senator's office say they use remote assistants—humans charged with responding to autonomous vehicles when they get confused, stuck, or in emergencies. The programs, experts say, are an important part of any autonomous vehicle company’s safety considerations, a backstop for a technology that’s becoming safer by the year but will continue to run into new situations on the road indefinitely. In a report also released Tuesday, Senator Markey said the new details were not enough. “Every autonomous-vehicle company refused to disclose how often their AVs require assistance from [remote assistants]—hiding key information from the public about their AV’s true level of autonomy,” he wrote. “This information is critical for lawmakers, regulators, and the public to understand the potential safety risks with AVs.” Markey called on the nation’s top federal road safety regulator to look more closely into autonomous vehicle companies’ remote assistance programs, and said he would soon introduce legislation responding to the “safety gaps” his investigation found. Remote-Controlled Robotaxis The responses from the autonomous vehicle developers show that, in one critical way, Tesla is an industry outlier. Six of the firms insisted that their remote assistance workers, who work across the US and even, in the case of Waymo, in the Philippines, never actually drive the vehicles directly. Instead, the humans provide input that the autonomous vehicle software then decides to use or ignore. Not so