Waymo have in house radar, I think in the 70GHz gap in the absorption spectrum. They're pretty obvious as sort of paperback book sized planes, mounted near other sensors IIRC.

The old Velodyne units were actually susceptible to damage if you left two units running right next to each other. I did hear a proposal at some point for a different but similar unit to use GPS time to sync the rotations of all the units we had live so they wouldn't be pointed at each other, but in practice it seemed to not be a huge issue.

BTW I once gave you guff about continuing to bring up Conti's flash LIDAR, and in retrospect I wish I hadn't, I really enjoy your contributions here.