In February, Senator Ed Markey (D-MA) sent letters to seven U.S. companies working on autonomous vehicle technology with a list of questions. He especially wanted to know how often these companies’ vehicles — operated by Aurora, May Mobility, Motional, Nuro, Tesla, Waymo, and Zoox — rely on input from remote staff. They all refused to say, according to the results of Markey’s investigation, which were released Tuesday. The information published by Markey’s office is the latest example of how hesitant autonomous vehicle companies are to share details about how their operations truly work — despite the fact that they are all experimenting with this technology on public roads. “This report has revealed a stunning lack of transparency from the AV companies around their use of [remote assistance operators] to help guide their AVs. The investigation exposed a patchwork of safety practices across the industry, with significant variation in operator qualifications, response times, and overseas staffing, all without any federal standards governing these operations,” Markey’s office wrote in its report. Markey said Tuesday that he is …