Because they use public infrastructure and in their passing almost exclusively move through spaces we share with them. This is a story, in part, about those ext

Because they use public infrastructure and in their passing almost exclusively move through spaces we share with them. This is a story, in part, about those externalities. As this author describes, linking extremely dangerous chemical cars onto an already overwhelmed structure means it's not if you will have another mass-casualty event[1], it's when. [1]: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1997246/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1997246/