Sure it was autonomous? Might be a mapping vehicle. Can’t see the front so don’t know what the forward sensors are. Robocars put their main focus on forward sensors, mapping vehicles more to the sides.
No idea on the dome, but it could be a secret sensor. Because LIDARs operate in the infrared, you can make a cover for them that is opaque to visible but transparent to infrared, but it would not normally be a cloudy white, I would think.