I drive a lot professionally, and on a daily basis I have to fix someone else´s mistake, and on a daily basis someone else will fix a mistake I make. The errors made by humans are a very large factor (probably more than 90%) of the accidents that we are involved in. At the same time the vast majority of would be accidents get fixed by our flexibility.
It makes me wonder if a human were at the wheel of that shuttle if the accident would have been avoided or not, it is not 100% clear cut to me that this accident would have happened in that scenario as well.
At a guess self driving cars will work very well with other self driving cars because they are hopefully never making any mistakes in the first place. But for now they will have to share the roads with us fallible humans and if that causes accidents like these to be far more frequent then that too is some kind of failure.