Self-driving vehicles being operated by Waymo, the autonomous driving division of Google, have been attacked or threatened at least 21 times since 2016.
Incidents have included a resident waving a hand gun at a passing Waymo car, being run off the road, tyre slashing, being assaulted with rocks, and verbal abuse.
In figures dug up by the Arizona Republic, police have recorded 21 incidents against Waymo vehicles in past two years since the company began testing its self-driving vehicles in the Phoenix area.
The newspaper understands the number of actual events may be higher because Google's backup drivers usually contact an internal dispatcher first, with police intervention only sought in more extreme cases.
Police reports seen by the Arizona Republic show Roy Leonard Haselton, a 69-year old man, was arrested in August 2018 and had his 0.22-calibre gun confiscated.
Haselton told police he pointed his gun "as the Waymo vehicle passed by and that his intentions were to scare the driver".
One Jeep driver has reportedly tried to run the company's vehicles off the road at least six times. On more than one occasion the Jeep intentionally drove head-on towards the autonomous car, while at other times the Jeep entered the Waymo people mover's lane and then slammed the brakes hard.
In another incident an inebriated 37-year old man stood, silently, in front of Waymo car in order to stop it from operating.
Waymo began testing its self-driving vehicles, including its fleet of Chrysler Pacifica plug-in hybrid people movers, in Phoenix, Arizona, in 2016. Late last year the company began limited commercial service in the same region.
With the company's technology still under development, all self-driving vehicles have a backup driver on-board, who can take over in an emergency, handle customer queries, and deal with incidents.