The report describes the progress of tank car safety upgrades from 2013 through 2020, by tank car type and type of flammable liquid. Class 3 flammable liquids most commonly include crude oil, ethanol, and refined petroleum products. 

In 2020, 111,177 rail tank cars were used to carry Class 3 flammable liquids, which 15% more than the 94,335 tank cars used in 2016. In 2016, only 8% of the fleet carrying crude oil and other Class 3 flammable liquids consisted of the DOT-117s which meet the new safety standards, compared to 54% in 2020, 

Survey results indicate that 7,413 DOT-117 and DOT-117R tank cars are projected to be built or retrofitted in 2021. 

The annual BTS report is required under the 2015 FAST Act (Fixing America’s Surface Transportation Act), Section 7308. Additionally, Section 7308(c) requires BTS to estimate the anticipated number of DOT-117 and DOT-117R tank cars for each year from 2018 through 2029 by collecting data from tank car shops that build or retrofit tank cars. It is expected that by the end of the transition period in 2029 all Class 3 flammable liquids will be carried in rail tank cars that meet or exceed the DOT-117 or DOT-117R specification.