It would have rear sensors. It knows something is behind at a fixed distance, so it must be matching your speed. If that distance is less than a safe reaction time, stopping is bad.

It knows stuff is happening to the sides and swerving is bad.

Unlike a human, it can slow down to hit the object at minimum speed, then speed up again just in time to not get hit even if the driver behind does nothing, at an optimized profile that gives the person behind time to not overreact and cause a pileup.

Self driving also has the advantage that people might stay away. Unlike regular tailgating you have machinephobia that might actually make people not tail you.

One of the most common accidents with "self driving" thus far has been the auto getting rear ended.

Yes, this is undoubtedly the human drivers fault for following too closely but ... is it being precipitated by unexpected AI braking? In any case, the AI has demonstrated very limited ability to avoid these sort of collisions.

I wonder why there aren't more devices to give you an insurance discount for following to close. Or just to make an unsilencable beep if you try.

In any case, some of those cases were probably due to lack of rear sensors, or lack of any sensors at all besides cameras, and lack of any deterministic code able to override the AI.

Tesla has two branches of their self driving software, the fsd branch which is under active development and the highway branch which has not had major changes in 2 years. The highway software is much worse around pedestrians and obstacles than FSD. It’s hard to say how fsd would handle a situation like that on the highway, but based on my experience with fsd off highway it would never choose to hit a car, so very likely it would run over the debris.