A week before Halloween last year, city of Austin employee Rachel Castignoli sent a polite but firm email to a government relations staffer at self-driving vehicle developer Cruise. "We would like you to not operate between 5 pm and 9 pm on Halloween," she wrote in bold text highlighted in yellow, documents obtained by WIRED through a public records request show. More children are killed by vehicles on Halloween than on any other night of the year, she wrote, and the city wanted to limit traffic--regardless of whether software or a human was behind the wheel. "Please acknowledge receipt of this email," Castignoli concluded, also in bold, adding "Thanks!" Castignoli's email is an example of the strange position of officials in some US cities chosen by Cruise and rivals such as Alphabet's Waymo as testing grounds for self-driving taxi services. Castignoli works for Austin's Transportation and Public Works Department, which like local agencies around the country, is responsible for what happens on city streets, setting speed limits and traffic restrictions.