There are simple low cost effective ways to reduce risk such as filling cars only half full that can be effected immediately.  Then there expensive actions that require both time and massive money such as replacing current oil cars.  Car replacement will take years.  So if safety was the real issue, we would not talk about leaving oil in ground, we would require trains at 20 mph, half full, with more frequent track inspection, etc.  (Short trains vs long does not have a clear correlation with safety.)  But the point is that once leaving the oil in the ground is mentioned, we are no longer talking safety.  If those worried stuck strictly to solutions to safety issues that are consistent with real current needs for oil, we might even get the safety issues addressed.  The instant leaving oil in the ground is mentioned, all safety related credibility is lost.