A 50,000-gallon crude-oil spill from a train derailment near Hattiesburg this year is one of several accidents that have transportation of hazardous materials under scrutiny.
The National Transportation Safety Board chairman last week included the derailment in a letter to two senators outlining safety concerns.
Christopher A. Hart, acting NTSB chairman, wrote the letter in response to the senators' questions on safe transportation by rail of flammable products.
The January derailment of 11 tank cars of a Canadian National train in New Augusta -- about 20 miles southeast of Hattiesburg -- spilled 50,000 gallons of crude oil, some of which made its way into a local waterway.
With a "dramatic rise" in transportation by rail of flammable products, safety issues are more pressing than ever, Hart wrote.
He cited the New Augusta derailment along with a 2013 accident in Minnesota and one in February in Pennsylvania.
"The NTSB has investigated numerous accidents in which all types of flammable materials have been released," Hart wrote. "We are aware of several accidents involving crude oil from other regions in which these products were released, causing environmental damage and fires."
n Have the Pipeline and Hazardous Materials Safety Administration and Federal Railroad Administration expand hazardous materials route planning to include trains transporting flammable liquids and to require rerouting to avoid populated and other sensitive areas.
n Have the PHMSA revise spill-response planning to include railroads in worst-case discharges. Require comprehensive response plans in accidents involving unit trains or blocks of tank cars transporting oil and petroleum products.
n Use more-robust tank cars to offer greater protection and reduce probability and consequences of releases in accidents.