In this case, the RPO clerks died by telescoping cars. After more years and more deaths in this manner, the Post Office issued standards for the construction of RPO cars to try to prevent such deaths. Existing cars would also require modifications for some of the changes.
So when I read the article, these cars with rail enforced ends are what I thought of. Those rails are on the end of this car because of regulations that were written by the blood of many RPO clerks.