"Petit began by recording pulses from a commercial Ibeo Lux Lidar unit. Discovering the pulses weren’t encoded or encrypted, he could simply use them at a later

"Petit began by recording pulses from a commercial Ibeo Lux Lidar unit. Discovering the pulses weren’t encoded or encrypted, he could simply use them at a later time to fool the unit into believing objects were there when they weren’t." That appears to answer my longstanding question as to what might happen when multiple vehicles using lidar are on the road at the same time. (Pulse timing notwithstanding of course, but given enough cars and enough time it could be periodically problematic.) However, regarding stopping a car with fake laser generated obstacles - that's nothing that can't be done with real "obstacles". A roll of paper or aluminium foil stretched across the road can't be discriminated from a solid object, and a a few empty cardboard boxes are as good as concrete blocks to a self driving car. Or even just standing in the road yourself if you have sufficient faith in the technology.