Radar on the Teslas, if it works like how I am familiar with, just detects "things". Things that have a decent radar return. This class of things does indeed

Radar on the Teslas, if it works like how I am familiar with, just detects "things". Things that have a decent radar return. This class of things does indeed include cars and other vehicles, but should also include walls and such. It is likely that they're using at least 2-D radar, so the system should be able to discriminate between an object directly in the path of travel, and one that is off to the side.