Source: Federal Rail Association (https://safetydata.fra.dot.gov/officeofsafety/publicsite/query/TenYearAccidentIncidentOverview.aspx) DM me for the .csv file. Data is available from 1975 to 2022.

Tool: Basic Plot in R

The plot shows total hazmat train derailment from 1997 to 2022 in the United States. The total derailment is divided by the total number of miles driven by trains for that year.

The lowest hazmat derailment per total train miles was in 1986 at 79.6 hazmat derailments/10 million miles (450 total that year). Notably , the total employee hours worked has been steadily decreasing since 1975. I am unable to tell whether there has been an increase or decrease in derailments due to changes in regulation.